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Metropolitan Washington RegionMetropolitan Washington RegionTraffic Signal SystemsTraffic Signal Systems

White PaperWhite Paper

FINAL DRAFT

Prepared for:Metropolitan Washington Council of Governments

May 29, 2002

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METROPOLITAN WASHINGTON REGION TRAFFIC SIGNAL SYSTEMS WHITE PAPER

Final Draft

May 29, 2002

EXECUTIVE SUMMARY1.0 INTRODUCTION............................................................................................................................................1

1.1 BACKGROUND..................................................................................................................11.2 PURPOSE...........................................................................................................................1

2.0 TRAFFIC SIGNAL OPERATIONS AND MAINTENANCE IN THE METROPOLITAN WASHINGTON REGION.............................................................................................................................2

2.1 TRAFFIC SIGNAL OPERATIONS.........................................................................................22.2 TRAFFIC SIGNAL MAINTENANCE.....................................................................................62.3 SURVEY RESULTS: JURISDICTIONAL SIGNAL SYSTEMS PROGRAMS...............................72.4 AGENCY COMMENTS ON SIGNAL SYSTEMS OPERATIONS.............................................172.5 AGENCY COMMENTS ON SIGNAL MAINTENANCE PROGRAMS......................................17

3.0 OPPORTUNITIES FOR COLLABORATION/ IMPROVEMENT PLANS.........................................19

4.0 CONCLUSIONS...........................................................................................................................................22

APPENDIX A: NARRATIVE SUMMARY OF AGENCY SURVEY RESULTS...............................................24

GLOSSARY..................................................................................................................................................................34

Traffic Signal Operations White Paper Trichord, Inc.Quality Consultants Group

EXECUTIVE SUMMARY

Severe traffic demands are being placed on the major arterials in the Metropolitan Washington region — no longer just during the typical weekday rush hour periods. Rather, these demands are occurring more frequently throughout the day, virtually every day. Many of these demands involve conflicting vehicular and pedestrian movements that require a high degree of traffic control to assign rights-of-way.

When incorporated into a system that operates interdependently, traffic signals are one of the best tools for state and local traffic engineers to use in addressing these traffic demands and conflicts — not only on corridors within particular jurisdictional boundaries, but throughout the Metropolitan Washington region.

Traffic engineers and transportation professionals in the Metropolitan Washington region face a number of technical challenges and resource conflicts in their quest to optimize traffic flow and signal coordination. At a technical level, traffic engineers address issues in signal coordination, communications, and traffic control strategies. At a financial resources and staffing level, traffic engineers address management, operations, and maintenance issues.

This traffic signal systems white paper summarizes the region’s capabilities in traffic control, signal operations, and system maintenance. It presents the results of a regional survey of signal system capabilities, categorizes the signal system capabilities, and identifies system characteristics by geographic area.

Throughout the Metropolitan Washington region, significant coordination of traffic signals occurs both within individual jurisdictions and between regional partners. There are currently several ongoing multi-jurisdictional traffic signal activities that promote regional objectives to improve traffic flow and safety in the region. These efforts, facilitated by the Metropolitan Washington Council of Governments (MWCOG), include the Pilot Arterial Corridor project, the regional traffic signal problem reporting system website, and the Traffic Signal Preemption/Priority study. From these activities, many regional partners have discovered unexpected similarities in their signal systems.

Each jurisdiction is trying to optimize the use of technology to save money. Integrated Traffic Management Systems (ITMS) is the next technological phase for many transportation agencies around the country — the Metropolitan Washington region is part of this evolution. The District of Columbia Department of Public Works currently has an ITMS initiative underway, which will integrate their arterial and freeway management operations (as well as some emergency services functions) into one center. It is envisioned that this effort will serve as a springboard for other agencies to begin considering the “hard” integration of functions and technologies to better serve their own needs, as well as the needs of the region.

Likely candidates for future potential opportunities involve those agencies that have both signal systems and freeway management system operations, e.g., CHART and Montgomery County’s ATMS, as well as VDOT’s Northern Virginia District Smart Traffic Center and its Traffic Signal System.

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All of the transportation agencies throughout the Metropolitan Washington region are taking tremendous advantage of the evolution of computer technology and using it to more efficiently and effectively operate and maintain their traffic signals and systems. Common areas of technology include the prevalent use of NEMA controllers and SYNCHRO optimization software, as well as system data archiving activities.

The region is performing well under difficult circumstances. In the face of limited staffing and funding, transportation agencies’ staff continue to find creative ways to use technology to help save time and money, as well as to maximize their limited dollars and staff - especially in the area of signal maintenance.

The region could perform better with additional resources. While all agencies are doing a great job with what they have, these transportation officials could do even more, if additional resources were made available, including:

More staff, in order to be more proactive and responsive in systems operations and maintenance (for example, increased staffing levels would enable the agency to perform signal retiming and optimization on a routine basis, to keep up with the real world fluctuations of traffic demand and citizens’ complaints)

Closed circuit television for remote system monitoring (to include verification and resolution of traffic and system problems before going out into the field; e.g. immediate adjusting of signal timings during an incident or identification of a signal bulb outage)

Video detection

Access to more communications infrastructure with greater bandwidth capabilities

Greater event tracking capabilities within the systems (created in a database format to enable query of activities)

Ability to observe signal operations in an off-line format

Communication between the on-street master controllers

Expanded master controller capabilities and functions

Better traffic signal coordination capabilities, specifically on side streets

Improvement of traffic responsive features to make procedures less cumbersome

Ability to review preemption information from a central location

Capability to work directly with optimization software from the system.

While facing the everyday reality of limited staffing and funding resources, these agencies still manage to take a proactive approach to traffic management by utilizing a variety of tools to mitigate the effects of increasing vehicular, bicycle, and pedestrian demands on the limited capacity of transportation facilities in the region.

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Although the functional responsibilities and the technical complexity and size of each agency’s systems vary, there is no doubt that each jurisdiction’s system functionality is very important plays a vital role in meeting the transportation goals of the regional transportation network. These transportation agencies are operating and maintaining their systems to meet a demonstrated need locally, while at the same time, also providing a valuable service and benefit to the region.

Traffic Signal Operations White Paper iii Trichord, Inc.Quality Consultants Group

1.0 INTRODUCTION

Severe traffic demands are being placed on the major arterials in the Metropolitan Washington region — no longer just during the typical weekday rush hour periods. Rather, these demands are occurring more frequently throughout the day, virtually every day, and many of these demands involve conflicting vehicular and pedestrian movements that require a high degree of traffic control to assign rights-of-way.

While there are various schools of thought on the need for traffic signals (and their advantages and disadvantages when installed), it has been shown that when a traffic signal is appropriately justified, properly designed, and effectively operated and maintained, it can be one of the best tools for state and local traffic engineers to use to address these traffic demands and conflicts.

When incorporated into a system that operates interdependently, traffic signals can be one of a jurisdiction’s most effective tools to assist in keeping traffic flowing in an efficient and safe manner — not only on corridors within its own jurisdictional boundaries, but throughout a region.

1.1 Background

In the 2000 The Region report (Vol. 39) published by the Metropolitan Washington Council of Governments, one of the main elements in Theme # 3 of the “Key Themes of the Vision” for the region is “the need to put together a package of projects to fund.” Within this element, projects were categorized into three (3) basic types: Fix-up, Enhancement, and Expansion.

In the “Fix-up” category, the report stated that “the region needs to invest more for fix-ups, such as sidewalk and traffic signal maintenance”; under the “Enhancement” category, the Council of Governments felt that investments in strategic improvements in areas such as traffic control would help the region get a lot more out of its existing transportation system. The implementation, operation, and maintenance of computerized traffic signals and systems is an example of one such strategic improvement being effectively used in the Metropolitan Washington region.

Because of the numerous jurisdictions in the Washington metropolitan region and the “invisible” jurisdictional boundaries that the traveling public experiences on these major highway corridors, it is critical that a high level of communication, coordination, and cooperation take place among responsible transportation agencies in traffic matters. In the Metropolitan Washington region, experience has shown that state and local transportation officials have taken a strong and visible leadership role to ensure that this takes place.

1.2 Purpose

The purpose of this paper is to document not only the technical aspects of the traffic signal system programs being operated and maintained around the Metropolitan Washington region, but also to highlight the creativity and successes of state and local transportation agencies in addressing the challenges and opportunities created by ever increasing traffic demands on limited capacity facilities — especially in the face of limited staffing and funding.

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2.0 TRAFFIC SIGNAL OPERATIONS AND MAINTENANCE IN THE METROPOLITAN WASHINGTON REGION

Traffic signals in the Washington, D.C. region are either a state or local matter – i.e., state and local transportation agencies are responsible for the justification, administration, installation, operations, and maintenance of traffic signals in their respective jurisdictional areas. These individual jurisdictions determine where, when, and how these signals are installed.

Once these signals are installed, however, officials do not just walk away from the devices and let them work on their own. The operations and maintenance of traffic signals are dynamic, day-to-day traffic management functions of state and local agencies, performed not only during rush hour periods, but also during incidents (vehicular and non-vehicular) and special events.

Many signals in the region operate without any relation to an adjacent jurisdiction’s signal operation. However, as land use development continues to increase and to expand along major regional corridors (usually resulting in the need for more signals), the likelihood of signals needing to work interdependently also increases.

2.1 Traffic Signal Operations

When operating a traffic signal system, the traffic engineer must consider a number of technical issues: signal coordination, communication methods, and control systems.

Signal Coordination: When a corridor has several signals in close proximity, the traffic engineer may find it beneficial to consider coordinating these signals to improve traffic flow. Several factors must be reviewed when considering coordination, including (but not limited to):

Traffic signal spacing Traffic volumes (vehicular and pedestrian) Turning movements Transit activity (loading and off-loading) Safety history On-street parking Traffic speed Land use

While the above factors are of a physical, measurable nature, the traffic engineer must also take into consideration those factors that may be somewhat more difficult to measure, such as driver comfort and satisfaction. The expectation of the typical “layperson” driver is to experience as smooth a ride as possible along a corridor, with minimal to no delay or random stops.

Figure 1 identifies which organization is responsible for signal coordination in different parts of the Metropolitan Washington Region.


Communications/Interconnection Methods: Once the decision to coordinate has been made, there are two basic methods that traffic engineers can consider to achieve interconnection: through a wire-line or a wireless communications connection.

Wire-line Connection. This method uses a physical wire connection to provide two-way communications between the controller assemblies in the field and/or back to a central control center. This direct connection can be achieved through various means — the most commonly used for signal communications in the Metropolitan Washington region being copper wire, coaxial cable, fiber optic cable, and leased lines.

Copper wire, also referred to as twisted pairs, is a widely used medium for interconnection of traffic signals. The copper cables are twisted in pairs in order to reduce electrical interference, or “cross-talk” – interference due to signal ingress in one communication channel caused by signal egress from an adjacent channel. This medium is mainly used for signal data transfer and has limited capacity for use with video.

Coaxial cable, initially used mainly by cable television service providers, has been found to have tremendous benefits to the transportation sector. Coaxial cable, also called “coax,” is a broadband communications technology that consists of a single inner conductor that has a


Virginia Department of Transportation

Maryland State Highway Administration

DC Department of Public Works

Montgomery County

Local Jurisdictions

FrederickCounty

LoudounCounty

Prince WilliamCounty

FairfaxCounty

Prince GeorgesCounty

Arlington County

Alexandria

Washington,DC

MontgomeryCounty

Figure 1: Organizations Responsible for Signal Coordination in the Metropolitan Washington Region

Fairfax

ViennaFalls

Church

City of Frederick

Herndon

Leesburg

ManassasPark

Manassas

Rockville

common axis with a second outer conductor (shield). This medium has the capacity of carrying many channels to transmit data, as well as video.

Fiber Optic cable is rapidly increasing in use by transportation agencies, due to its tremendous bandwidth capacity (compared to copper and coaxial cable). It is considered analogous to a multi-coaxial cable, but is much smaller physically, has much greater capacity, can carry a signal over long distances, and is virtually immune to electromagnetic interference, because it transmits light pulses (rather than an electrical signal).

Leased Lines are generally telephone-type twisted pairs or fiber optic cables that are leased by transportation agencies from a local communications company. A major drawback to using leased lines is the high on-going lease costs that are sometimes tied to the service provider’s general service rate increases.

Wireless Connection. While not commonly done with traffic signals, transportation agencies may also utilize wireless connections, such as radio or time-based coordination to achieve interconnection.

Radio systems are a form of wireless communication connection and come in various forms, including cellular networks, satellite, and spread spectrum radio. While still not widely used for traffic signal operations, there are special circumstances where radio may be the best communications media to utilize. Examples of such circumstances include situations where there are no available landlines or when right of way is not available for communications infrastructure installation. There are disadvantages to radio, however, including line of sight requirements, fading issues, and limited bandwidth capacity.

Time-based coordinators are also used to achieve communications between signals without cables. These time-based coordinators are basically accurate internal clocks that supervise a local controller unit by sync pulses and commands, similar to a master controller. Interconnection is achieved when several adjacent controllers are similarly equipped and operate from the same time reference point. The obvious drawback to this method is that two-way communication between controllers cannot be achieved, and the need for the clocks to be updated on a routine basis to ensure accuracy.

Figure 2 identifies the communication methods used for traffic signal systems in different parts of the Metropolitan Washington Region.


Control Systems: There are several control systems available for signal system operation. Three types of control systems in operation in the Metropolitan Washington region include: (1) central control systems, (2) closed loop systems, and (3) hybrid systems.

1. Central control systems involve a computer control system in which the master computer, central communication facilities, console, keyboard, and display equipment are all situated at one location (e.g. a signal operations center). This approach can include the use of a master controller to control cycle lengths, offset and split for each cycle; or, a mutually coordinated system of intersections that does not require a master controller. Signal system staff coordinate and control traffic signals throughout a defined geographic area from the signal operations center.

2. Closed loop systems provide two-way field communication between the intersection signal controller and its master controller. The master controller then communicates information back to the signal operations center.

3. Hybrid systems are a combination of various control systems, strategies and technologies that a jurisdiction implements in a systematic fashion (e.g., time-based coordination, isolated intersections, etc.).


Agency-owned Copper Wire

Combination of Agency-owned Copper and Fiber

Leased Lines

Agency-owned Copper Wire,Fiber, and Leased Lines

Leased Fiber

Combination of Owned Copper& Leased Lines

Information Unavailable

Figure 2: Communication Methods

FrederickCounty

LoudounCounty


FairfaxCounty Prince Georges

County

Washington,DC

MontgomeryCounty

Fairfax

Vienna

Herndon

ManassasPark

Manassas

Rockville

Arlington County

Alexandria

Falls Church

City of Frederick

Leesburg

These computerized signal systems, with their communications links, provide great operations and maintenance benefits to transportation agencies’ staff. Personnel can use these systems to (remotely) monitor and adjust signals, as well as to respond more efficiently to incidents (e.g., adjusting signal timing in real-time during incidents and special events).

Figure 3 identifies the types of control systems used in different parts of the Metropolitan Washington Region.

2.2 Traffic Signal Maintenance

With all agencies experiencing increasing demands on their transportation infrastructure, as well as their staff, maintenance is a critical element in the success or failure of their signal system programs. There are several types of signal maintenance activities that a jurisdiction can undertake. The three main categories include: 1) repair maintenance (malfunction and breakdown), 2) preventive maintenance, and 3) response maintenance.

1) Repair Maintenance covers two basic areas: malfunction and breakdown.

a. Malfunction: any event that impairs the operation without losing the display and sequencing of signal indications to approaching traffic. Malfunctions include


Central

Closed Loop

Hybrid

Unknown

FrederickCounty

LoudounCounty


FairfaxCounty

Prince GeorgesCounty

Washington,DC

MontgomeryCounty

Figure 3: Control Systems

Fairfax

Vienna

Herndon

ManassasPark

Manassas

Rockville

Arlington County

Alexandria

Falls Church

City of Frederick

Leesburg

timing failures, detection failures (vehicle and pedestrian), loss of interconnected control, and other similar occurrences.

b. Breakdown: any event that causes a loss of signal indication to any or all phases or traffic approaches. Breakdowns include controller unit failures, controller cabinet equipment failure, cable failures, loss of power, and signal lamp burnout, leaving no indication visible.

2) Preventive Maintenance: Checks and procedures to be performed at regularly scheduled intervals for the upkeep of traffic signal equipment. This includes inspection, cleaning, replacement, and record keeping.

3) Response Maintenance: Procedures and repairs made in the event of reported failed traffic signal equipment and its restoration to safe, normal operation.

Benefits Of Maintenance Programs: Computerized systems and technology can reduce demands on limited agency manpower, and improved design of these systems can further assist an agency to offset system maintenance and related costs. Even with good system design, there are even more significant benefits that can be gained through a formal, properly funded and staffed maintenance program, regardless if an agency’s system is “high tech” or not. On the other hand, if signal maintenance is not performed on these systems consistently, negative impacts can quickly result, including poor signal operations that can result in increased stops and delay, vehicular and pedestrian safety concerns, unstable traffic flow, congestion, increased emissions, etc.

2.3 Survey Results: Jurisdictional Signal Systems Programs

Seventeen agencies throughout Maryland, Northern Virginia, and Washington, D.C. are responsible for the administration, implementation, operation, and/or maintenance of signal systems. These agencies were recently interviewed to gather technical information on their current signal system programs, as well as their thoughts and concerns on their systems’ effectiveness.

Sixteen of these agencies with operations and maintenance responsibilities are listed in Tables 1 - 9, along with their systems’ attributes. Fairfax County, which allows the Virginia Department of Transportation (VDOT) to operate and maintain its signals, is not included in the table, but rather, is represented by VDOT.

Detailed summaries for each agency’s signal system program, can be found in Appendix A of this document. These summaries are based on the survey responses received from agency personnel.


System TypeSystem Type Operating SystemOperating System CommunicationsCommunicationsOptimizationOptimization

SoftwareSoftware ControllersControllers

Traffic SignalTraffic Signal Management Management

Support SoftwareSupport Software Other System FeaturesOther System Features

Central Control

Closed Loop Hybrid

OS/2 or

UNIXWin

95/98/NT

Copper Fiber

SYNCHRO Other NEMA 170 MONARC Other

Priority Detection

Archive DataOwn Lease Own Lease

Fire, Rescue Transit Video Loop

Microwave Infrared/Radar

DCDPW/DCDOT X X X NT X X X QuicNet X X

MDSHA X X NT X X X X ARIES X X X X

Montgomery County X UNIX NT X X X Custom X COMTRAC X X X Microwave Radar

Prince Georges County X NT X X N/A N/A X Street-wise

Virginia DOT X OS/2 NT X X X X X MIST X X Microwave X

Arlington County X X OS/2 95, NT X SCOOT X X (SCOOT)

X UW X X Infrared X

Fairfax County X

City of Alexandria Client server NT X X X TSP4 X X X X X X X

City of Fairfax X OS/2 X X X X X X Radar X

City of Falls Church Time-Based Coord.

? ? X ? ? X ? ? X X

City of Frederick X N/A N/A X N/A N/A X N/A N/A X X X

Town of Herndon UW NT N/A N/A N/A N/A UW X Peak X UW X

Town of Leesburg X NT N/A N/A N/A N/A PASSER X PASSER UC X X

City of Manassas X NT X X X VMS 330 X X X

City of Manassas Park X X X N/A N/A X ? X X X ?

City of Rockville X 98 X X X X Aries X X UW

Town of Vienna X 98, NT X X X LM X LM X

Key: N/A – Not Applicable UW – Underway ? – Information Not Available UC – Under Contract 11/12/01 – MWCOG

TABLE 1: MWCOG Region Traffic Signal Systems - Signal System Features and Capabilities


Control SystemsControl Systems Signal Optimization SoftwareSignal Optimization SoftwareCentralCentral ClosedClosed

LoopLoopHybridHybrid SynchroSynchro ScootScoot PasserPasser OtherOther NoneNone

DCDPW/DOT MDSHA Virginia DOT City of Alexandria TSP4Arlington Co. (UTCS)City of Fairfax (SIM Traffic)City of Falls Church N/A N/A N/A N/A N/ACity of Frederick Town of Herndon UW N/A N/A N/A N/A N/ATown of Leesburg (NETSIM)City of Manassas (SIM Traffic)City of Manassas Park ? ? ? ? ? ? ?Montgomery Co. CustomPrince Georges Co. City of Rockville Town of Vienna LM

N/A – Not ApplicableUW – Underway? – Information Not Available

Table 2: Control Systems and Optimization Software


FreeFree OperationOperation

Fully-Fully-ActuatedActuated

Semi-Semi-ActuatedActuated

FlashFlash Time-basedTime-based CoordinationCoordination

TrafficTraffic AdaptiveAdaptive

TrafficTraffic ResponsiveResponsive

Time ofTime of DayDay

Pre-TimedPre-Timed

DCDPW/DOT MDSHA Virginia DOT Testing Testing

City of Alexandria Arlington Co. City of Fairfax City of Falls Church City of Frederick Town of Herndon Town of Leesburg City of Manassas City of Manassas Park ? ? ? ? ? ? ? ? ?

Montgomery Co. Prince Georges Co. City of Rockville Town of Vienna


Table 3: Control Strategies


ControllersControllers CommunicationsCommunicationsType 170Type 170 NEMANEMA Copper*Copper* Fiber*Fiber* LeasedLeased

LinesLinesRadioRadio Time-basedTime-based

CoordinatorsCoordinatorsDCDPW/DOT MDSHA Virginia DOT City of Alexandria Arlington Co. City of Fairfax City of Falls Church City of Frederick Town of Herndon N/A N/A N/A Future Town of Leesburg City of Manassas City of Manassas Park ? ? ? ? ? ?

Montgomery Co. Prince Georges Co. UW

City of Rockville Town of Vienna

N/A – Not ApplicableUW – Underway? – Information Not Available* - Agency Owned’

Table 4: Controllers and Communications


MonarcMonarc MistMist ScootScoot PasserPasser QuicNetQuicNet OtherOther

DCDPW/DOT MDSHA ARIES

Virginia DOT City of Alexandria Arlington Co. City of Fairfax City of Falls Church ? ? ? ? ? ?

City of Frederick N/A N/A N/A N/A N/A N/A

Town of Herndon TCT-LM

Town of Leesburg City of Manassas VMS 330

City of Manassas Park ? ? ? ? ? ?

Montgomery Co. COMTRAC

Prince Georges Co. Streetwise

City of Rockville Aries

Town of Vienna LM


Table 5: Traffic Signal Management Software


InductiveInductive LoopsLoops

VideoVideo MicrowaveMicrowave MagneticMagnetic ProbesProbes

RadarRadar InfraredInfrared

DCDPW/DOT MDSHA Virginia DOT City of Alexandria Arlington Co. City of Fairfax City of Falls Church City of Frederick Town of Herndon UW

Town of Leesburg City of Manassas City of Manassas Park ? ? ? ? ? ?

Montgomery Co. Prince Georges Co. MicroCity of Rockville Town of Vienna


Table 6: Detection


OpticalOptical Push ButtonPush Button AudibleAudible GPSGPS

DCDPW/DOT (F&R, T)MDSHA (F&R, T) (F&R)Virginia DOT (F&R) (F&R) (F&R)City of Alexandria (F)Arlington Co. (F&R, T-U) (F&R)City of Fairfax (F)City of Falls Church (F)City of Frederick (F)Town of Herndon (F&R)Town of Leesburg UW

City of Manassas (F&R, P)City of Manassas Park ? ? ? ?

Montgomery Co. (F) (T)Prince Georges Co. (F)City of Rockville

Town of Vienna

Fairfax Co. (F&R) (F&R)

F – FireR – RescueT – TransitP – PoliceN/A – Not ApplicableUW – Underway? – Information Not Available

Table 7: Preempt / Priority


WIN 3.1WIN 3.1 WIN 95WIN 95 WIN 98WIN 98 WIN NTWIN NT OS/2OS/2 UNIXUNIX VMSVMS DOSDOS

DCDPW/DOT MDSHA Virginia DOT City of Alexandria Arlington Co. City of Fairfax Future City of Falls Church ? ? ? ? ? ? ? ?

City of Frederick ? ? ? ? ? ? ? ?

Town of Herndon Town of Leesburg City of Manassas City of Manassas Park ? ? ? ? ? ? ? ?

Montgomery Co. Prince Georges Co. City of Rockville Town of Vienna


Table 8: Operating Systems


OracleOracle SQLSQL DBase IVDBase IV SyBaseSyBase OtherOther

Data Archived?Data Archived? Database Schema Available?Database Schema Available?

YesYes NoNo YesYes NoNo

DCDPW/DOT MDSHA ? ?

Virginia DOT City of Alexandria Arlington Co. City of Fairfax City of Falls Church ? ? ? ? ? City of Frederick Town of Herndon Town of Leesburg ? ? ? ? ? City of Manassas City of Manassas Park ? ? ? ? ? ? ? ? ?

Montgomery Co. Prince Georges Co. City of Rockville Access Town of Vienna


Table 9: System Databases


2.4 Agency Comments On Signal Systems Operations

Overall, the majority of those agencies which have computerized systems have found that their systems are easy to operate and user friendly, resulting in their ability to do their jobs in a more proactive and efficient manner. Agency personnel feel that these systems and technologies enable them to quickly respond to citizens’ complaints and system problems.

Staff engineers and technicians feel that these systems also make it easier to manipulate traffic data and to more rapidly create (or modify) timing plans. The ability to remotely perform this data collection, as well as the uploading and downloading of traffic signal timings to intersections, is a major plus to optimizing traffic flow. Collection and utilization of real-time traffic data offers significant benefits to the agencies, as they are able to gain more knowledge and a better, more realistic understanding of the traffic demands on their roadway systems.

Staff from one Signals Operations Center indicated that their system has the capacity to provide comprehensive failure reports for communications and controller status, system and local flash operation, and status of system timing plans. This feature allows them to more accurately determine system problems and in turn, provide better and more expedient response maintenance.

Others noted that they like the variety of features found in their systems, such as the closed-loop system operation, alternate phasing sequences, and transit priority control capabilities. These additional features allow them to be more creative in finding solutions to traffic problems, and also gives them the ability to assist a variety of transportation modes, such as transit, in providing better service to their customers.

2.5 Agency Comments On Signal Maintenance Programs

Many agencies agree that having computerized systems help them tremendously in their maintenance activities, as they are able to more quickly respond to repair needs (due to increased accuracy in defining the problem). One agency noted that their maintenance costs have decreased significantly (95%) due to their ability to replace computers more quickly and at lower costs.

Preventive Maintenance Programs: All of the agencies in the region with traffic signal responsibilities have some form of a Preventive Maintenance program, although they vary according to system size and sophistication, as well as maintenance staffing levels and schedules.

Some agencies in the region have no set schedule for preventive maintenance work, while others have preventive maintenance work scheduled as frequently as every 90 days, others do the work every six months, and still others schedule preventive maintenance annually or every two years.

Several agencies have defined schedules for certain pieces of equipment, such as signal heads being replaced every two years and going into controller cabinets to do preventive maintenance at least once a year. Still other agencies base their preventive maintenance schedules on field versus system devices. For some, the goal is to do preventive maintenance work on field devices annually, and system devices every two years.


Contract maintenance is used by those agencies with limited maintenance staff. One agency reported that while contract maintenance is conducted annually, their practice is that whenever a signal is upgraded, the contractor is directed to check out everything related to that signal and to repair anything needed at that time.

Response Maintenance Programs: All area jurisdictions responded that they have response maintenance criteria to follow when dealing with repair calls. In response to the question of “target times” for repairing non-functioning traffic signals, the answers varied based on signal location and time of day. However, the general time range for response maintenance functions runs from “immediately” to 24 hours.

With regard to geographic location, for one agency, the response times vary from three hours if the signal is in a downtown area, to five hours for those in residential areas.

For those that have time-of-day criteria, most stated that their target time ranges from “immediately” and “15 minutes” during business hours to “longer after working hours.”

One agency stated that their response maintenance was “immediately, if not sooner. The longest ever was two hours.”

Some agencies noted that they have staff on 24-hour call for signal maintenance and this helps them greatly in their efforts to be immediately responsive to traffic signal malfunctions or breakdowns.

Signal Program Administration and System Constraints: Even with all of these technical advantages and benefits, most agencies find that some limitations still exist in their signal system programs. However, they recognize these as opportunities to creatively improve the systems in order to do their jobs even more efficiently and effectively.

All agencies felt that additional staff support and funding would be extremely helpful, allowing them to operate their systems in such a manner that they could perform even more traffic management functions to assist in mitigating traffic congestion, unnecessary stops and delays.

Having additional technology resources was also noted as something that would be beneficial. For example, some feel that video-based features (such as video detection and CCTV) would allow agency personnel to better monitor traffic conditions and remotely adjust/change signal timing, as needed. It is felt that this would be a more proactive and efficient way of addressing traffic signal problems, instead of having to rely on citizens’ complaints and/or radio traffic reports of malfunctioning signals. There are also issues with technology (controllers) becoming obsolete, resulting in poor vendor support and increased costs.

Communications issues were noted by several agencies, from those who had no communications infrastructure in place at all (but need it), to those who felt their system’s performance was hampered due to communications bandwidth limitations.


Custom features were also noted as potential trouble spots – one agency noted that the process to create reports was cumbersome (due to a custom reporting feature), making the process time consuming.

Desired Additional Program Administration and Signal System Features: While all agencies are doing a great job with what they have, these transportation officials could do even more, if additional resources were made available. Some of the features that agencies would like added to their programs and systems include:

More staff, in order to be more proactive and responsive in systems operations and maintenance (for example, increased staffing levels would enable the agency to perform signal retiming and optimization on a routine basis — to keep up with the real world fluctuations of traffic demand and citizens’ complaints)

Closed circuit television for remote system monitoring (to include verification and resolution of traffic and system problems before going out into the field; e.g. immediate adjusting of signal timing during an incident or identification of a signal bulb outage)

Video detection


Greater event tracking capabilities in the systems (created in a database format to enable query of activities)








Although the functional responsibilities and the technical complexity and size of each agency’s systems vary, there is no doubt that each jurisdiction’s system functionality is very important and plays a vital role in achieving the transportation goals of the regional transportation network. These transportation agencies are operating and maintaining their systems to meet a demonstrated need locally, while at the same time, also providing a valuable service and benefit to the region.

3.0 OPPORTUNITIES FOR COLLABORATION/ IMPROVEMENT PLANS

While there are significant benefits to providing and conducting good traffic operations and maintenance practices within a single jurisdiction, even greater gains can be achieved when State and local transportation agencies jointly pursue and initiate collaborative efforts in traffic operations and maintenance across jurisdictional borders. Not only can these efforts maximize


the effectiveness of an agency’s limited resources, but they can also provide tremendous benefits to the traveling public such as smoother traffic flow, and reduced delays and stops along a corridor.

Opportunities for cooperation between State and local transportation agencies can take the form of either technical or institutional collaboration, and can often be accomplished at very low (to no) cost to an agency. Examples of technical collaboration include activities such as:

Signal coordination on an arterial corridor across jurisdictional borders Signal timing optimization along a corridor.

For example, in order to move traffic smoothly along an arterial corridor that goes through more than one jurisdiction, traffic engineers in neighboring jurisdictions may decide to coordinate their traffic operations, e.g. use the same cycle length along the corridor.

Institutional collaboration can be accomplished between agencies in many ways, including:

Joint procurement and possible sharing of signal equipment Development, endorsement, and implementation of similar signal timing plans Sponsor and conduct joint training courses for staff, and Knowledge transfer among staff.

An example of knowledge transfer could involve sharing the expertise of one agency’s staff in a particular area. For example, many systems in the region utilize NEMA controller technology. If there is a state or local traffic engineer or signal technician who has considerable experience and expertise in the operations and maintenance of NEMA controllers, this knowledge and wisdom could be shared with other agencies that may have limited or no staff with knowledge or experience in this area.

As another example, joint training courses could be arranged for regional participants. The work of MWCOG’s Professional Capacity Building Working Group could be used to identify joint training needs and opportunities.

The Metropolitan Washington region has already recognized the tremendous benefit of collaborative efforts in the area of traffic signals and systems. There are currently several ongoing multi-jurisdictional traffic signal activities that promote regional objectives to improve traffic flow and safety in the region. These efforts, facilitated by the Metropolitan Washington Council of Governments, include the Pilot Arterial Corridor project, the regional traffic signal problem reporting system website, and the Traffic Signal Preemption/Priority study. These efforts all serve as models of collaborative regional efforts in which an agency can participate with minimal disruption to its ongoing traffic signal system program.

Another potential area of collaboration involves traffic data. The majority of agencies surveyed currently do some level of traffic data archiving, and the remaining agencies have plans to do so in the future. This data is a valuable resource, not only to traffic signal-related functions, but also for regional transportation and land use planning activities and (as evidenced recently) in


incident and evacuation activities. Being able to share this data with minimal, if any, need for database modifications would be of tremendous benefit to the region. Agencies could consider utilizing database programs that ease the sharing of data across jurisdictional lines.

There are still other opportunities for collaboration worthy of review by area transportation and other governmental agencies. A major goal for the Metropolitan Washington region is to optimize traffic flow for all travelers. To that end, the majority of agencies surveyed have underway (or will in the near future) programs geared towards optimizing signal timings to improve traffic flow. This activity can yield tremendous “bang for the buck,” being one of the most cost-effective measures an agency can take using existing resources.

While this optimization is geared towards improving traffic flow for all travelers, state and local agencies are also sensitive to the special traffic flow needs of their partners in the transit and emergency services communities, and are seeking safe and efficient ways to assist them in this area.

For example, the Metropolitan Washington region is becoming more and more transit-dependent as single occupant vehicular (SOV) congestion continues to increase on the highway network. Transportation officials feel that transit is a valuable alternative for travelers to consider to help address this congestion problem, and recognize that providing reliable, high quality and expedient transit service is a must to lure these travelers out of private automobiles.

With this in mind, traffic engineers throughout the region are exploring incorporating transit-related features into their (current and future) signal systems. This includes utilizing system hardware, software and/or communications features that can be easily adapted to assist in the functionality of a current and future transit signal priority system and/or AVL transit fleet activities.

These types of signal design considerations can also be applicable to any effort involving the safe and efficient routing of emergency response vehicles, such as fire and rescue units, as well as police. Many jurisdictions already have some basic level of preemption infrastructure in place for these emergency responders. It is most likely that, as the public safety need increases and the technology matures, these systems will also become a part of traffic signal system operations.

By considering transit and emergency services needs in the design, upgrade and operations phases of signal systems, transportation agencies will be ensuring that technologies, systems, and organizations work together in a safe and cost-effective manner to accomplish the individual jurisdictions’ goals, as well as the region’s goals.

Integrated Traffic Management Systems (ITMS) is the next technological phase for many transportation agencies around the country — and the Metropolitan Washington region is part of this evolution. The District of Columbia Department of Public Works currently has an ITMS initiative underway, which will integrate their arterial and freeway management operations (as well as some emergency services functions) into one center.


Likely candidates for future potential opportunities involve those agencies that have both signal systems and freeway management system operations, e.g., CHART and Montgomery County’s ATMS, as well as VDOT’s Northern Virginia District Smart Traffic Center and its Traffic Signal System.

4.0 CONCLUSIONS

All of the transportation agencies throughout the Metropolitan Washington region are taking tremendous advantage of the evolution of computer technology and using it to more efficiently and effectively operate and maintain their traffic signals and systems. In addition to this observation, several other conclusions were drawn based on the survey data.

Throughout the Metropolitan Washington region, significant coordination of traffic signals occurs, both within individual jurisdictions and between regional partners. There are currently several ongoing multi-jurisdictional traffic signal activities that promote regional objectives to improve traffic flow and safety in the region. These efforts, facilitated by the Metropolitan Washington Council of Governments (MWCOG), include the Pilot Arterial Corridor project, the regional traffic signal problem reporting system website, and the Traffic Signal Preemption/Priority study. From these activities, many regional partners have discovered unexpected similarities in their signal systems.

Each jurisdiction is trying to optimize the use of technology to save money. Integrated Traffic Management Systems (ITMS) is the next technological phase for many transportation agencies around the country and the Metropolitan Washington region is a part of this evolution. The District of Columbia Department of Public Works currently has an ITMS initiative underway which will integrate their arterial and freeway management operations into one center (as well as some emergency services functions).

All of the transportation agencies throughout the Metropolitan Washington region are taking tremendous advantage of the evolution of computer technology and using it to more efficiently and effectively operate and maintain their traffic signals and systems. Common applications of technology include the use of NEMA and Type 170 controllers and SYNCHRO optimization software, as well as system data archiving activities.

The region is performing well under difficult circumstances. In the face of limited staffing and funding, transportation agencies’ staff continues to find creative ways to use technology to help save time and money, as well as to maximize their limited dollars and staff - especially in the area of signal maintenance.

The region could perform better with additional resources. While all agencies are doing a great job with what they have, these transportation officials could do even more, if additional resources were made available, including:

More staff, in order to be more proactive and responsive in systems operations and maintenance (for example, increased staffing levels would enable the agency to perform


signal retiming and optimization on a routine basis — to keep up with the real world fluctuations of traffic demand and citizens’ complaints)

Closed circuit television for remote system monitoring (to include verification and resolution of traffic and system problems before going out into the field; e.g. immediate adjusting of signal timings during an incident or identification of a signal bulb outage)

Video detection


Greater event tracking capabilities in the systems (created in a database format to enable query of activities)








While facing the everyday reality of limited staffing and funding resources, these agencies still manage to take a proactive approach to traffic management by utilizing a variety of tools to mitigate the effects of increasing vehicular, bicycle, and pedestrian demands on the limited capacity transportation facilities in the region.

Although the functional responsibilities and the technical complexity and size of each agency’s systems vary, there is no doubt that each jurisdiction’s system functionality is very important and offers a valuable service to the transportation goals of the regional transportation network. These transportation agencies are operating and maintaining their systems to meet a demonstrated need locally, while at the same time, also providing a valuable service and benefit to the region.

Traffic signals are an everyday occurrence for many travelers in the Metropolitan Washington region; therefore, it is of the utmost importance that traffic engineers and signal technicians make every effort to ensure that these devices are being operated and maintained to the highest possible degree of safety and efficiency.


APPENDIX A: NARRATIVE SUMMARY OF AGENCY SURVEY RESULTS

DISTRICT OF COLUMBIA DEPARTMENT OF PUBLIC WORKS/DOT

The Washington, DC Signal Operations Center (SOC) is located in the Public Works Department. There are 25 staff-persons who operate and maintain the central control system (10 field technicians, five office personnel and 10 consultants who are engineers and technicians). The system includes 1,500 traffic signals that function in fully-actuated, time-based coordination and/or pre-timed mode. It is estimated that five to ten traffic signals are added to the system each year. Type 170E controllers are currently used, but the agency is transitioning to 2070E. There are 500 inductive loops, three video detection and 100 microwave detection devices. Fifty percent of system detection is on-line using agency-owned copper lines. (The plan is to go to all fiber in the future).

QuicNet 4.0 is the software application that is used to support the management of the traffic signal system. The agency uses a Windows NT operating system, with a LAN network and TCP/IP protocol. An SQL database archives system data but a copy of the agency’s database schema is not available. The hardware used to operate the system includes six IBM Netfiniti servers with ten operator interfaces, using 256M of RAM with a hard disk size of 30GB. The central processing units (CPU) operate at a speed of 500 MHz. The system provides remote dial-in capabilities using landlines. Currently, the District has plans to do a complete system upgrade.

A priority control system for Fire and Rescue, as well as police operations, is in place (42 optical units); fire and EMS personnel have access to these devices. There are three vehicles with AVL/GPS capabilities. There are 40 Opticom units installed for transit priority, mostly along Georgia Avenue (no GPS capabilities). There are twelve closed circuit television (CCTV) cameras currently in operation, with plans to install three hundred more cameras in the future.

MARYLAND STATE HIGHWAY ADMINISTRATION

The Signal Operations Center (SOC) and the Statewide Operations Center are located at the Office of Traffic Safety, in Hanover, Maryland. The Signal Operations Section contains approximately 40 field technicians who operate and maintain the SHA's network of traffic signals and traffic signal systems. This network includes approximately 1500 traffic signals operating in either "free" (fully actuated) mode, time-based coordination, or as part of a closed loop system. Approximately 50 new traffic signals are added to the system each year, using NEMA controllers. The closed loop systems contain approximately 1000 inductive "sampling loops" used for system data collection.

The agency’s operating system is DOS, Windows 3.1 and Windows NT, with an Oracle database (system data is archived). The network is Netware and Windows NT-based, using IPX and TCP/IP protocols. There are approximately four operator interfaces. SYNCHRO is the software application used for optimization. The system has remote dial-in capabilities utilizing agency-owned fiber and copper lines, as well as cellular communication.


Preemption/priority control devices (250 optical and 100 push button) are deployed by the agency for fire and rescue services. Priority control devices (50 optical) are deployed by the agency for transit operations. There are no GPS capabilities associated with either the preemption or priority control devices at this time.

Approximately 100 intersections are now using video detection technology, with an additional 100 to have video detection installed shortly.

VIRGINIA DEPARTMENT OF TRANSPORTATION

The Northern Virginia District Traffic Signal System (NOVA TSS) is located in Arlington, Virginia. There are 45 employees assigned to the TSS (28 field technicians and 17 control room staff) to operate and maintain the central system, which includes 946 traffic signals running in free operation (fully and semi-actuated) and time-based coordination modes (also, testing traffic adaptive and traffic responsive modes). It is estimated that 50 traffic signals are added to the system each year. NEMA and Type 170 controllers are in use (though VDOT is in the process of replacing all NEMA controllers with Type 170s). There are 10,000 inductive loops, 25 microwave detectors, and 4 magnetic probe devices deployed in the field. Ninety-eight percent of the detection is on-line using leased lines.

MIST is the software application that is used to support the management of the traffic signal system. The hardware used to operate the system includes nine servers (8 Dell, 1 DEC Alpha),. The servers’ central processing units (CPU) run at 450Mhz, with 256MB/1GB of Random Access Memory (RAM) and 27GB of hard drive space. There are 14 personal computers (Dell Optiplex); eleven operating at a CPU speed of 450Mhz and 3 at 400 MHz. They are equipped with 256MG of RAM and 9GB of hard drive space. Four workstations (Dell Precision) operate at a CPU speed of 450MHz, with 1GB of RAM and 9GB of hard drive space. There are 30 operator interfaces.

The agency’s operating systems are Windows NT and OS/2 (soon NT only). The database application is Sybase (the database schema is currently available). The network is OS/2 (LAN server) and NT, using the TCP/IP protocol. SYNCHRO is the software application used for signal optimization (system data is archived for future use). The system provides remote dial-in capabilities using landlines. Currently, VDOT has plans to upgrade the operations center equipment (25% equipment replacement per year based on useful life of five years; all equipment recently upgraded in March 1999).

There are no closed circuit television (CCTV) cameras in use by the TSS. Preemption/priority (optical, audible and push button) are in use for Fire & Rescue operations and is deployed at the Lansdowne Hospital entrance. There are no GPS capabilities or preemption/priority strategies for transit operations.


CITY OF ALEXANDRIA, VIRGINIA

The Signal Operations Center (SOC) is located in the City Hall Building in Alexandria, Virginia. Approximately 5 field technicians and 3 control room employees operate and maintain the closed loop system, which includes 230 traffic signals running in free operation (fully actuated) and/or time-based coordination mode. It is estimated that five to ten traffic signals are added to the system each year. NEMA, NEMA-TS2-1, and NEMA-TS2-2 controllers are used. There are 560 inductive loops, 20 microwave detectors, and 3 devices for video detection.

MONARC is the software application that is used to support the management of the traffic signal system. The hardware used to operate the system includes two Compaq servers, four Dell personal computers, and one Compaq workstation; there are three operator interfaces. The agency’s operating system is Windows NT and the database is SQL compliant (the database schema is not available). The network information was not available but the agency is using the TCP/IP protocol. TSP4 is the optimization software used by the City; if volume information is available, SYNCHRO 4.0 is also used for signal optimization (system data is archived for future use). The system provides remote dial-in capabilities using agency-owned twisted pair copper landlines.

Currently, the City does not have plans to upgrade the operation center equipment, as a recent replacement was just completed. Four Closed Circuit Television (CCTV) cameras, manufactured by Pelco, are used at selected intersections throughout the City. In addition, preemption/priority devices (15 optical) for Fire & Rescue operations are deployed, with the Fire Department having access. There are no GPS capabilities or preemption/priority strategies for transit operations.

ARLINGTON COUNTY, VIRGINIA

The Signal Operations Center (SOC) is located in the Traffic Engineering Division of the Department of Public Works in Arlington, Virginia. Approximately 7 field technicians and 2 control room operators operate and maintain the hybrid control system, which includes 248 traffic signals running in free operation (semi-actuated); time based coordination; and/or traffic adaptive modes. It is estimated that four traffic signals are added to the system each year. NEMA-TS2-1 and NEMA-TS2-2 controllers are used by the County. There are 190 inductive loops, one infrared detector, and one device for video detection. Ninety-five percent of the system detection is on-line using agency-owned copper lines.

MONARC and SCOOT are the software applications used to support the management of the traffic signal system. The hardware used to operate the system includes three Pentium II personal computers (PC), and four Pentium II workstations. The central processing units (CPU) for the workstations run at 350MHz, with 96MB of Random Access Memory (RAM) and 8.4GB of hard drive space. The three personal computers function as system servers, which operate using the following:

1. MONARC (fixed time system) using a Pentium II processor with a CPU speed of 350MHz, 64MB of RAM, and 4.3GB of hard drive space.


2. SCOOT (traffic adaptive system) using a 433MHz DEC Alpha CPU, with 128MB of RAM and 4.3GB of hard drive space.

3. SCOOT (communications server) using a Pentium II processor with a CPU speed of 350MHz, 128MB of RAM, and a 9.1GB SCSI hard drive.

The agency’s operating systems are Windows NT, OS/2, VMS, and Windows 95. The database is SQL compatible (the database schema is not currently available). The network is OS/2 and Windows NT, using NETBIOS/NETBEUI and TCP/IP protocols. The UTC system with a SCOOT model attached to it is the software application used for signal optimization (system data is not archived). There are presently six operator interfaces. The system provides remote dial-in capabilities using agency-owned copper landlines. Currently, the SOC does not have plans to upgrade the operation center equipment.

Preemption/priority devices for Fire and Rescue operations are deployed at twelve intersections (10 push button and two optical). There are no GPS capabilities or preemption/priority strategies for transit operations at the present time; however, the County is in the process of putting transit priority on Columbia Pike. No CCTV is currently in place.

FAIRFAX COUNTY, VIRGINIA

VDOT owns and maintains the signal systems in Fairfax County. However, the County does have a computer terminal where it can access traffic signal and traffic count data. The County suggests timing changes to VDOT and works with the Traffic field operations group on traffic signalization safety issues. The County does provide funding for traffic signals and developers are also required to install new signals that are related to their development, or to escrow the monies towards a future signal. Only two (2) counties in the Commonwealth of Virginia control their own signals; one is Arlington County.

Fairfax County currently deploys preemption/priority devices – four (4) optical, 16 push buttons, and four (4) which are a combination of optical and push button. Agencies with access to the preemption are Fire and Rescue, including EMS and Suppression units. The County currently has no transit-based preemption/priority but is experimenting with a system on U.S. Route 1.

CITY OF FAIRFAX, VIRGINIA

The City of Fairfax, Virginia operates its own traffic signal system. The City maintains an operations center at the Property Yard located at 3410 Pickett Road. Seven crew maintain signs and signals and one supervisor oversees the operations. The supervisor performs signal timing and optimization functions. The City has recently assigned a staff member to assist the supervisor on a part time basis to help perform optimization. The City operates approximately 50 traffic signals and adds on average one new signal each year.

The City of Fairfax operates a closed loop system. MONARC is the software application used to support the management of the signal system. SYNCHRO is used for signal optimization. The


computer used to manage the signal system is an OS/2 based personal computer. The City is upgrading to a windows based operating system. The City does not normally archive data but will perform data archiving on special request. The City uses priority/preemption at four major intersections for fire and emergency vehicles.

CITY OF FALLS CHURCH, VIRGINIA

Signals are operated by the City of Falls Church in Falls Church, Virginia (though there is no actual Signal Operations Center building in place). Approximately 1.5 staff persons operate and maintain the hybrid system, which include 30 traffic signals running in time-based coordinated mode, using NEMA controllers. No traffic signals are added to the system each year. There are 110 inductive loops in operation. Only two traffic signals are on-line using agency-owned copper.

A single personal computer is used to operate the system; no other system information is available. SYNCHRO 4.0 is the software application used for signal optimization (system data is not archived and a database schema is not available). The system provides remote dial-in capabilities using agency-owned copper landlines. Currently, there is no plan to upgrade the signal operation equipment.

There are no Closed Circuit Television (CCTV) cameras in use. Preemption/priority (four units) for Fire operations are deployed. There are no GPS capabilities or preemption/priority strategies for transit operations.

CITY OF FREDERICK, MARYLAND

Signal operations duties are handled in Frederick, Maryland, with a signal operations center under development. Approximately 14 staff members operate and maintain the closed loop system, which includes 72 traffic signals running in time based coordination and/or traffic responsive mode (plus actuation). All of the downtown area is under closed loop operation. It is estimated that two traffic signals are added to the system each year, using NEMA controllers. Agency-owned copper is presently assigned for use on the closed loop system (also one radio link). There are 90 inductive loops, with none of the detection presently on-line (but plans are underway to put them on-line and is estimated to be completed one year from now).

No software application is presently used for the management of the traffic signal system. No detailed hardware or network information was provided.

Information on the agency’s operating system was not provided. The database application utilized is Hanson (the database schema is not currently available). The system does not currently include remote dial-in capabilities.

Currently, plans are under development for an SOC with servers, fiber connections and eventually CCTV cameras. Preemption/priority (one push button) for Fire operations is deployed


at the Fire Department. There are no GPS capabilities or preemption/priority strategies for transit operations.

TOWN OF HERNDON, VIRGINIA

The Signal Operations Center (SOC) is located in Herndon, Virginia. Two staff members are assigned to operate and maintain the signal system, which include 30 traffic signals running in time-based coordination mode. The closed loop system is under construction and should be completed by late summer/early fall. It is estimated that one to two traffic signals are added to the system each year. NEMA TS-1 controllers are used, with 325-350 inductive loops in operation; video detection is to be added at one intersection soon. None of the detection is currently on-line; field site visits are required to download the data.

An old DOS-based version of Peak’s closed loop system software is the application that is used to support the management of the traffic signal system. Pentium computers are proposed for the new system, with the central processing units (CPU) operating at speeds of 166Mhz, with 64 Mb of Random Access Memory (RAM) and 2GB of hard drive space. There are two operator interfaces in the system.

The database is SQL compatible (the database schema is not available). Currently, the system data is not archived. There are plans underway for the upgrade of the SOC equipment. The new equipment will include a closed-looped system, with the communications medium obtained through the use of radios transmitting on fixed frequencies (frequencies have already been obtained by the FCC).

Preemption/priority (one push button) is deployed for Fire and Rescue services. There are no GPS capabilities or preemption/priority strategies for transit operations. Closed Circuit Television (CCTV) cameras are not currently in use.

TOWN OF LEESBURG, VIRGINIA

The Town manages the traffic signal system functions in Leesburg, Virginia (currently no signal operations center built). One full-time traffic engineer maintains the hybrid signal system, which includes 22 traffic signals running in time-based coordination mode (with internal time clocks). It is estimated that two traffic signals are added to the system each year. NEMA controllers are used, with inductive loops in operation. None of the detection is currently on-line, as there presently is no signals communications infrastructure in place. (The town has funds for a communication system but not put out for bid yet).

PASSER is the application that is used to support the management of the traffic signal system. While there are plans to build an SOC, only laptops are currently used to upload and download signal timings and change and coordinate program values and settings. The agency’s operating system is Windows NT and system data is archived regularly (the database schema is not available).


Closed Circuit Television Cameras (CCTV) and preemption/priority devices are not currently in use, although there is a contract under development that will put in preemption/priority devices for Fire and Rescue services at five intersections next summer.

CITY OF MANASSAS, VIRGINIA

The Signal Operations Center (SOC) is located in the Public Works Department, in Manassas, Virginia. Approximately 2 field technicians and 1 control room operator (Director and Lead Technician share this role) maintain the hybrid system, which include 45 traffic signals running in time based coordination, traffic responsive (only on one corridor) and/or free operation at night (fully-actuated). It is estimated that two traffic signals are added to the system each year. NEMA-TS2-1 controllers are used. There are 600 inductive loops, 1 infrared detector, and 1 device for microwave detection. 95% of the detection is on-line using agency- owned fiber lines.

IDC VMS 330 is the software application used to support the management of the traffic signal system. The hardware used to operate the system includes two 486 servers. The agency’s operating system is Windows NT, using NETBIOS protocols. SYNCHRO is the software application used for signal coordination and optimization (system data is archived for future use and a copy of the agency’s database schema is available). The system provides remote dial-in capabilities using landlines. Currently, the SOC has plans to upgrade the operation center equipment within the next year.

Opticom preemption/priority devices for Fire/Rescue and Police operations are deployed on all signals (for use by surrounding jurisdictions as well). There are no GPS capabilities or preemption/priority strategies for transit operations, and Closed Circuit Television Cameras (CCTV) are not currently deployed.

CITY OF MANASSAS PARK, VIRGINIA

Signal operations are conducted in the City of Manassas Park, Virginia. Three and one-half staff members are assigned to operate and maintain the signal system, which includes six traffic signals running in free operation mode. The signals are a part of a closed loop system. No traffic signals are added to the system each year. NEMA controllers are used, with 20 inductive loops in operation as well as eight (8) video detection units. One intersection is currently on-line via a dial-in landline.

The City uses a Windows-based operating system. No network protocol, operator interfaces or servers currently exist. WinTV software is used for the video, and Econolite's proprietary software in conjunction with WinTV. Pentium computers are used in the system.

There currently is no system database; therefore, a database schema is not available and no system data is archived. There are no plans underway for the optimization of the signal system.


The communications medium is copper wire. The City plans to upgrade its operation center equipment eventually, within the next five to seven years.

Preemption is deployed for Fire and Police services at four (4) intersections but with no GPS capabilities. There are no preemption/priority strategies for transit operations. Eight (8) Econolite Closed Circuit Television (CCTV) cameras are currently in use.

MONTGOMERY COUNTY, MARYLAND

The Signal Operations Center (SOC) is located in the Traffic Management Center (TMC) in the Department of Public Works and Transportation, in Rockville, Maryland. Approximately six control room operators and 20 field technicians operate and maintain the central (hybrid) control system, which includes 748 traffic signals running in free operation (fully and semi-actuated); time of day; and/or traffic responsive modes. It is estimated that 6-10 traffic signals are added to the system each year, using NEMA and NEMA-TS2-2 controllers. There are 1000’s of inductive loops, approximately 24 microwave detectors, 30 devices for video detection, and several magnetic probe and radar devices. Over one thousand (1000) sampling detectors are on-line using agency-owned copper, fiber lines and leased lines.

A COMTRAC system using Fortran/Assembler language programs (running a data general mini computer operating system, utilizing DT-200 communications over FSK 1800 baud) is used to support the management of the traffic signal system. The hardware used to operate the system includes Unix Sun Sparc servers and workstations, Windows 95, 98 and 2000, Data General MV9600a, sun ULTRA Sparc servers, and Linux computers. The central processing units (CPU) for workstations run from 75MHz to 500MHz for PC’s and 300+MHz Sun Sparc, with 32Mb-1Gb of Random Access Memory (RAM) and 1 Gb-60Gb of hard drive space. There is RAID systems and disk arrays that can store a half a terabit worth of data for archive, backup and online needs.

The agency uses Windows NT, UNIX, and Windows 95-98 operating systems. The database is Informix SQL (the database schema is available). The network uses TCP/IP protocols (system data is archived). The system provides remote dial-in capabilities using land and cellular (Virtual Private Network – VPN) lines. Currently, the TMC has plans to upgrade the operation center equipment beginning within the next 6 months (upgrade to some servers and workstations to a Windows 2000 platform, enhance and upgrade the Unix servers as well).

Preemption devices are deployed at twenty intersections (push buttons in the fire house) for Fire services. There are also priority request devices on all of the Ride On transit vehicles, with GPS capabilities. One hundred and thirty (130) CCTV cameras, manufactured by Diamond Electric, are in operation.


PRINCE GEORGES COUNTY, MARYLAND

The Signal Operations Center (SOC) is located in Prince Georges County, Maryland. Approximately four field technicians and two system operators operate and maintain the closed loop system, which includes 150 traffic signals running in free operation (fully and semi-actuated), time of day, and/or time base coordination mode. It is estimated that three traffic signals are added to the system each year, using NEMA controllers. There are over 1200 inductive loops, 12 video detection units, and 10 magnetic loops. Ninety percent of the detection is on-line using agency-owned lines.

Streetwise by Naztec Inc is the software application used to support the management of the signal system. The hardware used to operate the system includes two Dell computers. The central processing units (CPU) for workstations are Pentium II, running at 300MHZ, with 128Mb of Random Access Memory (RAM) and 6.4 Gb of hard drive space.

The agency’s operating system is Windows NT. The County has no network at this time, although future plans call for a Windows NT platform. The database is dBase IV (the database schema is not currently available). System data is not currently archived. The County currently does not have a network but there are plans to acquire one. The system provides remote dial-in capabilities using landlines. Currently, there are plans to upgrade the SOC equipment within the next year.

One pushbutton preemption device is deployed at one firehouse location No CCTV is currently in place but there are plans to install one unit within the year.

CITY OF ROCKVILLE, MARYLAND

The City’s Signal Operations Center (SOC) is located in Rockville, Maryland. One office and two field staff persons operate and maintain the hybrid signal system, which includes 39 traffic signals running in time-based coordination mode. It is estimated that two traffic signals are added to the system each year. NEMA controllers are used, with 35 inductive loops and five video detectors in operation. Ninety percent of the detection is on-line using leased lines. Remote dial-in capability exists over landlines.

Aries is the software application that is used to support the management of the traffic signal system. Personal computers are used to upload and download signal timings and change and coordinate program values and settings. The agency’s operating system is Windows 98, and system data is not currently archived. The agency’s database schema is not available. There are plans to upgrade the operation center equipment (the goal is to eventually monitor traffic using cameras from the office). Preemption/priority devices and Closed Circuit Television Cameras (CCTV) are not currently in use.


TOWN OF VIENNA, VIRGINIA

The Signal Operations Center (SOC) is located in Vienna, Virginia. One staff person operates and maintains the closed loop signal system, which includes 14 traffic signals running in free operation (fully and semi-actuated) and/or time-based coordination mode. No traffic signals are added to the system each year. NEMA controllers are used, with 93 inductive loops in operation. None of the detection is currently on-line; but a technician can monitor this from the master controller in the field.

LM System is the software application used to support the management of the traffic signal system. Two personal computers are used to upload and download signal timings and change and coordinate program values and settings. System data is not archived and the agency’s database scheme is not available. Remote dial-in capability exists but is not functional at this time. There are plans to upgrade the operation center equipment in two years.

Preemption/priority devices and Closed Circuit Television Cameras (CCTV) are not currently in use.


GLOSSARY

Actuation: the operation of any type of detector. The word “operation” means an output from the detector to the controller unit.

Adaptability: the quality of a traffic control system to maintain system operations over an extended time period under changing conditions.

Arterial System: a linear sequence of signals on an arterial supervised to provide progressive flow.

Arterial System Control: a type of control applied to two or more traffic signals to ensure progressive traffic flow.

Bus Priority: cycle-by-cycle timing of a traffic signal so the beginning and end times of green may be shifted to minimize delay to approaching buses. The normal sequence of signal displays is usually maintained.

Closed Loop Signal System: a system that provides two-way communication between the intersection signal controller and its master controller. The master controller communicates to the signal operations center.

Coaxial Cable (coax): a broadband communications technology with the capability of carrying many channels to transmit either data or video. Contains a single central conductor having a common axis with a second outer conductor.

Communication Link: the means of connecting one location to another in order to transmit and receive data.

Communication Network: a composite of communications links

Communication System: the composite of communications links and associated communications equipment, which interconnect all the control and surveillance components of a traffic control system.

Conflict Monitor: an electrical device that checks the green and yellow indications for each phase to protect against improper conflicting signals. Provides an output in response to conflict.

Congestion: a freeway condition where traffic demand exceeds roadway capacity. Normally occurs during peak travel periods or when a traffic incident reduces capacity by creating a bottleneck.

Controller Assembly: a complete electrical mechanism mounted in a cabinet for controlling the operation of a traffic control signal.

Controller Hardware – Solid State: solid-state controller assemblies include the controller unit, conflict monitor, auxiliary devices and terminals.


Controller Unit: the part of the controller assembly that performs the basic timing and logic functions.

Coordination: the establishment of a definite timing relationship between adjacent traffic signals.

Cycle: in a pre-timed controller unit, a complete sequence of signal indications. In an actuated controller unit, a complete cycle is dependent on the presence of calls on all phases.

Cycle Length: the time required for one complete sequence of signal phases.

Dedicated Lines: communication lines used solely to interconnect two or more locations not normally switched.

Detector: a device for indicating the presence or passage of vehicles or pedestrians. This general term is usually supplemented with a modifier, i.e., loop detector, magnetic detector indicating type.

Downloading: a function of a traffic system whereby the master controller can access the local controller’s memory to update or modify a stored timing plan or controller settings.

Emergency Vehicle Preemption: the transfer of the normal control of signals to a special signal control mode for emergency vehicles.

Fiber Optics: a broadband communication technology based on an optical waveguide that channels the light in the fiber with total internal reflection at the boundary.

Flow Rate: number of vehicles passing a point on the roadway during a specified time period.

Fully-Actuated Control Assembly: a type of traffic-actuated controller assembly in which means are provided for traffic actuation on all approaches to an intersection.

Incident: an occurrence in a traffic stream that causes a reduction in capacity or abnormal increase in demand. Common incidents include accidents, stalled vehicles, spilled loads, etc.

Inductive Loop Detector: a pavement installed active device that senses a decrease in loop inductance during vehicle presence.

Infrared Detector: passive and active above-ground mounted devices used for pedestrian and/or vehicle presence. Some devices provide counts, speed, length, and queue.

Integrated Traffic Management System (ITMS): the system that integrates all hardware and software elements of transportation management within a geographical region. It includes: traffic signal systems; freeway management systems; traveler information systems; and incident management systems.

Interconnected Signal System: a number of intersections that are connected by wire, radio, or some other means to effect traffic progression.


Isolated Local Controller: a local controller that is a stand-alone unit and a unit times right-of-way assignments independently of other controllers.

Local Controller Assembly: a controller assembly supervising the operation of traffic signals at a single intersection.

Local Controller: Pre-Timed: a device that controls all timing intervals to a fixed pre-determined plan. Works best where traffic is predictable and constant.

Local Controller: Full-Actuated: a device that controls the length of all timing intervals based on detected traffic demand on the associated approach. Adjusts cycle and split to fit changing demands.

Local Controller: Semi-Actuated: a device that controls some approaches on the basis of detected traffic demand. Non-actuated phases receive a minimum green interval that extends until interrupted by actuation on other phases.

Local Signal Preemption: the emergency or transit vehicle transmits a signal to the intersection controller where a special control phase assigns right-of-way.

Magnetic Detector: a pavement installed device of coiled wire with a highly permeable core. Vehicle induced flux changes cause an induced voltage pulse. Not to be confused with a magnetometer detector.

Magnetometer Detector: a pavement installed device that detects change in the vertical component of the earth’s magnetic field caused by the presence of a vehicle. Not to be confused with a magnetic detector.

Master Controller Assembly: a controller assembly for supervising multiple secondary controller assemblies and/or multiple sub-master controller assemblies.

Model (type) 170 Controller: one of two types of the most commonly installed and available intersection controllers. Specifications jointly developed by California and New York. Specifications include sections on electronic modules, connectors, wiring, harnesses, and cabinet enclosures.

Model 2070 Advanced Transportation Controller: the next generation of traffic signal controller under the Model 170 line. A microprocessor based controller using OS-9 real-time operating system, with VERSA Module Eurocard (VME) backplane and Motorola 680X0 processor family.

NEMA Controller: The second of the two most commonly installed and available intersection controllers. Adopted by electrical equipment manufacturers.

Network Signal Control: control techniques that are applicable to a signalized roadway grid network. Grid network imposes control constraints including common cycle lengths and closed loop sum of offsets that must be an integral number of cycle lengths.


Offline: descriptive of a system, peripheral equipment, or a process not under the control of a central processing unit.

Online: descriptive of a system, peripheral equipment, or a process under the control of a central processing unit.

Optimization Programs: programs that compute and evaluate the effects of various sets of signal timing on vehicle flow within a given network. These programs determine optimal timing plans and/or evaluate a given timing plan.

Phase: the portion of a traffic cycle allocated to any single combination of one or more traffic movements simultaneously receiving the right-of-way during one or more intervals.

Phase Sequence: a predetermined order in which the phases of a cycle occur.

Preemption: the transfer of the normal control of signals to a special signal control mode.

Preemption/Priority Systems: preemption control of normal signal timing plans applies in the following situations: signals adjacent to railroad crossings; emergency vehicle priority movement and priority for transit vehicle. Preemption occurs on a single cycle basis.

Preemptive Devices: provide priority for fire and emergency vehicles by detecting the vehicle and sending the preemption command to the controller.

Pre-Timed Controller Assembly: a controller assembly for the operation of traffic signals with predetermined fixed cycle lengths, fixed interval duration, and fixed interval sequence.

Probe: the sensor form that is commonly used with a magnetometer-type detector.

Progression: term used to describe the progressive movement of traffic through several intersections within a control system without stopping.

Radar/Microwave Detectors: pole-mounted radar device that can sense speed and passage and/or presence, when activated by a vehicle passing through its RF field.

Radio Communication: radio frequency transmission using any one of the following techniques: cellular networks; satellite transmission; packet radio; and spread spectrum radio.

Sampling Detector: any type of vehicle detector used to obtain representative traffic flow information.

Semi-Actuated Traffic Controller Assembly: a type of traffic-actuated controller assembly in which means are provided for traffic actuation of one or more, but not all, approaches to an intersection.

Signal Timing: the amount of time allocated to each interval/function in a signal cycle.


Supervisory Local Controller: a control device ranging from a time-base coordination unit to a remote master controller that determines or alters interval duration and/or maintains timing relationships in a group of local controllers.

Sync Pulse: a pulse generated from a central point that provides a common time base to all coordinated traffic controller units and which is used to provide a smooth flow of traffic through coordinated intersections.

Time-Base Signal Coordination: a controller technique that changes timing plans on an internal time basis.

Time-Based Coordination (TBC) Control: TBC control permits system operation of pre-timed and traffic actuated local controllers without (physical) communication links or master controller units. TBC can be implemented in all NEMA TS2 and Model Type 170 controllers, and some TS1 controllers.

Time-Of-Day (TOD) Operation: signal timings plans selected according to the time of day.

Traffic-Responsive Signal Control: the feature of an open or closed loop field master controller that changes intersection signal timing based on information from system detectors.

Traffic Responsive System: a system in which a master controller either selects or computes signal timing based on the real-time demands of traffic as sensed by vehicle detectors.

Vehicular Volume: the number of vehicles passing a given point per unit of time.

SOURCES

Traffic Control Systems Handbook – Publication No. FHWA-SA-95-032. U.S. Department of Transportation/Federal Highway Administration, February 1996

Traffic Engineering Handbook. Institute of Transportation Engineers, 4th edition


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