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Traffic Impact Study Guidelines

Maryland Department of Transportation

State Highway Administration

DRAFT March 15, 2017

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Table of Contents

Introduction....................................................................................................................................3

Application of Guidelines...........................................................................................................3

Scoping and Study Area..................................................................................................................4

Study Area..................................................................................................................................5

Multi-jurisdictional Considerations for TISs................................................................................7

Example Report Outline.............................................................................................................7

Existing, Background, and Projected Traffic Conditions..................................................................9

Existing Conditions.....................................................................................................................9

Background Conditions..............................................................................................................9

Projected Conditions................................................................................................................10

Data Needs and Considerations....................................................................................................10

Traffic Counts...........................................................................................................................10

Other Traffic Data.....................................................................................................................12

Trip Generation............................................................................................................................12

Trip Generation Rates..............................................................................................................12

Trips Generated by Existing Development...............................................................................12

Pass-by Trips.............................................................................................................................13

TOD Consideration...................................................................................................................13

Trip Distribution............................................................................................................................13

Modal Split...................................................................................................................................13

Trip Assignment............................................................................................................................13

Traffic Analysis/Network Evaluation.............................................................................................14

Analysis Tools...........................................................................................................................14

Model Calibration.....................................................................................................................14

Measures of Effectiveness/Results to Report...........................................................................17

Mitigation/Recommendations......................................................................................................19

Identification of Deficiencies/Mitigation Thresholds................................................................19

Summary of Mitigation.............................................................................................................21

General Considerations............................................................................................................21

Appendix A: Sample TIS Scope of Work Form...............................................................................23

Working Draft 03.16.2017

IntroductionThe purpose of a Traffic Impact Study (TIS), prepared for submittal to the Maryland Department of Transportation - State Highway Administration (MDOT-SHA), is to review impacts of a proposed development or redevelopment on the safety of the State Highway System in conjunction with the issuance of an access permit. The authority to require a TIS and related roadway improvements is found in COMAR Section 11.04.05.L.

“Traffic Impact Study. At the discretion of the State's engineer, applicants for a major development or a development that may have a significant impact upon the State's highway system, or both, shall submit a traffic impact study to determine the type of access and scope of required highway improvements required to accommodate the proposed development.”

The intent of MDOT-SHA’s TIS guidelines is to provide guidance regarding the information necessary for SHA to assess potential safety issues associated with a significant development’s access to the State Highway System, and to maintain consistency with County/local jurisdiction APFOs for proposed developments or redevelopments when appropriate, and to the extent possible.

Application of Guidelines

In order to address the safety impacts to the State Highway System, a TIS should adequately identify traffic capacity, signalization, safety, and multimodal issues.

Many counties/jurisdictions have established Adequate Public Facilities Ordinances (APFOs) which outline their requirements for TIS report preparation. The following list summarizes situations regarding the appropriate application of county/jurisdictional APFOs and MDOT-SHA guidelines:

At the discretion of the MDOT SHA District Engineer, a TIS may be required by MDOT-SHA for any proposed development that generates 50 or more peak hour trips, or any redevelopment that generates 50 or more peak hour trips over the existing site development.

For those counties/jurisdictions that have not established their own APFOs relating to traffic impact studies, where MDOT-SHA determines the potential for a significant roadway safety concern where an MDOT-SHA Access Permit is needed, MDOT-SHA’s traffic impact study guidelines and procedures should be followed.

In some cases, where MDOT-SHA determines the potential for a significant roadway safety concern attributable to the proposed development, or redevelopment may not be adequately addressed through County/jurisdictional APFOs, the following supplemental guidelines and procedures established by MDOT-SHA for traffic impact study report preparation and traffic mitigation may be necessary. Any questions with respect to applicability to these supplemental guidelines and procedures should be established during initial scoping for the TIS.

In cases where no MDOT-SHA Access Permit is needed, the following guidelines and

procedures established by MDOT-SHA may be used as guidance for the applicable county/jurisdiction where development or redevelopment is proposed.


Scoping and Study AreaA TIS is meant to evaluate how traffic safety on a roadway network will be affected due to trips generated by a proposed development. Generally, this evaluation considers operations and safety within a study area under existing, background traffic, and projected (or total traffic) conditions. The TIS will analyze the site access to the State road, will identify traffic safety deficiencies attributable to the proposed development, and identify any planned mitigation. Identification of deficiencies may include any queuing, storage, blockage, delay, weaving, merging, diverging, or other safety issues.

Prior to the development and submittal of a TIS, the developer/applicant typically participates in an initial scoping process (meetings, e-mail correspondence, or other mode of communication) in cooperation with the appropriate local jurisdiction(s), to discuss and establish site specific criteria, including but not limited to: study area, site and background trip generation, analysis time frame, and analysis methodology for the TIS. While not required, ideally, such discussions should involve MDOT-SHA engineers/planners.

To better facilitate discussion and streamline the scoping process, a scope of work or similar form can be completed and submitted to the appropriate representatives of MDOT-SHA’s District Office for review and concurrence. The purpose of this form would be to document results of the discussion held during the scoping process (e.g. determining site specific criteria for the development, including but not limited to: study area, trip generation, analysis time frame), and to establish a mutual understanding of the elements to be included as part of the TIS report. A sample Scope of Work form can be found in Appendix A. It is optional for the applicant/consultant to populate and submit this specific Scope of Work form in Appendix A to MDOT-SHA. The information requested in the form should be provided to MDOT-SHA in a clear, written format during the scoping process, such that MDOT-SHA can better facilitate its own TIS review. Requested information that is not provided may result in the need for TIS revisions and/or a delay in approval of the TIS.

During the scoping process, SHA should inform the developer whether the requirements for a TIS of a local APFO will be adequate for SHA review and whether any additional or alternative study may help supplement SHA’s evaluation of the proposed development’s impacts to the State Highway system.

Once a scope has been established and it is determined that an Access Permit is required from SHA, the applicant/consultant is expected to develop and submit a TIS Report to both MDOT-SHA and to the appropriate County/local jurisdiction for review.

It should be noted that MDOT-SHA’s role and approval of a TIS pertains to the analysis of a development’s proposed safety impacts on the surrounding roadway network and any required mitigation within MDOT-SHA right-of-way. Final approval of the proposed access concept will be determined as part of the Access Permit plan review process.


Study Area

An important part of the TIS and early scoping is the establishment of a project study area. The extent of the study area to be included in the analysis associated with a TIS should be based on the maximum peak hour trips generated by the proposed development. The number of peak hour trips expected to be generated by the development is based on local trip generation rates; trip generation rates from non-local sources but for similar developments, facilities, and operational conditions; or the latest version of the ITE Trip Generation Manual:

Small Development: 50 – 100 Peak Hour Trips Medium Development: 101 – 750 Peak Hour Trips Large Development: > 750 Peak Hour Trips

Table 1 provides a quick reference for determining the extent of a typical study area, with study areas extending greater distances from the site access driveways as the development peak hour trip generation values increase. Information pertaining to typical operational analysis tools and mitigation will be discussed in subsequent sections. Site specific issues and/or conditions, such as the presence of a signal system, adjacent signalized intersections or interchanges just outside of the study area, and/or other constraints may result in the addition or exclusion of intersections to the study area. These site specific issues, as well as the appropriate study area, should be discussed and established during the initial scoping for the TIS.

During scoping, any site specific issues/conditions, such as the presence of a signal system, adjacent signalized intersections just outside of the study area, any specific unsignalized intersection(s), any relevant freeway segments or interchange ramps, and/or other constraints, should be discussed to determine the appropriate study area for an individual project. This may result in addition or exclusion of study intersections and roadway segments per Table 1, but would result in a study area that accurately captures the impact of a proposed project.

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Table 1: Quick Reference: MDOT-SHA Traffic Impact Study Guidelines

Type of Development

Peak Hour Trips

GeneratedStudy Area

Typical Operational

Analysis Tools - Examples

Mitigation

Small 50-100

Intersections Boundary

Critical Lane Volume (CLV)

Highway Capacity Software (HCS)

Synchro/SimTraffic

SIDRA

VISSIM

Other as needed

With APFO: Improve LOS for overall intersection and individual movements to thresholds established in APFO.

With No APFO: Improve LOS and associated delay for overall intersection and individual movements to:

o Background Condition LOS and delay if Background Condition already reflects LOS ‘E’ or ‘F’.

o LOS ‘D’ if Background Condition reflects LOS ‘D’ or better.

Any storage or blocking issues caused by the development.

Any merge, diverge, weaving issues caused by the development.

Site access driveways

All intersections involving State highways and all intersections of a State highway and county/local collectors (or higher functionally classified roadways)

Within ¼ mile radius of

outermost site access driveways

Medium 101-750

Within ½ mile radius of

outermost site access driveways

Large > 750

Within minimum 1 mile radius of outermost site

access driveways

*During scoping, any site specific issues/conditions, such as the presence of a signal system, adjacent signalized intersections just outside of the study area, any specific unsignalized intersection(s), any relevant freeway segments or interchange ramps, and/or other constraints, should be discussed to determine the appropriate study area for an individual project. This may result in addition or exclusion of study intersections and roadway segments per the above table, but would result in a study area that accurately captures the impact of a proposed project.

Working Draft 03.16.2017 6

Multi-jurisdictional Considerations for TISs

The specific impact area to be considered in a multi-jurisdictional TIS should be defined at scoping. If the development/redevelopment is substantial in scope, is in close proximity to adjacent counties or municipalities, or if it is determined that the local APFO does not provide sufficient guidance in evaluating potentially significant safety/operational concerns for highways in adjacent jurisdictions, applicants for MDOT-SHA highway access permits should consider inclusion of cross-jurisdictional impacts on the State’s highway system in the TIS. That is, County and/or municipal boundaries should not always be the determining factor for where traffic impacts will be evaluated and mitigated.

When a proposed access point meets the following criteria, a multi-jurisdictional traffic impact study may be required:

If the local APFO or other public infrastructure assessment framework does not consider the traffic impacts of development beyond the jurisdiction of origin, and

If the access point is within the following radial distances, based on development size, from an adjacent County or municipality:

o ¼ mile for a small developmento ½ mile for a medium developmento 1 mile for a large development

Example Report Outline

This example report outline below can be used as a guide for formatting a TIS for submittal to MDOT-SHA.

Table of Contents

Introduction

o Explanation of Project/Purpose of Report

o Area Map showing site location (including any new proposed access points or use of existing access points)

o List and area map of intersections included in the analysis

o Brief description of key roadway and roadside characteristics (e.g. roadway classification, cross-section, posted speed limit, non-motorized access, pedestrian, bicycle, transit facilities)

o Mile point of the development along the road of the primary access point

o Land use for the proposed development


o Forecasted total trips entering and total trips exiting the site due to the proposed development

o Proposed build-out year to be used

Existing Conditions

o Traffic counts (volume diagrams) and analysis

o Existing lane configuration sketch (up to date, scalable aerial photography may be used as well)

o Existing traffic operations relating to the study area

Background Conditions

o Application of annual growth in existing traffic to build-out year of proposed development, if appropriate, as stipulated through scoping

o Traffic generated by other approved, but currently unbuilt, developments

o Background Analysis (Background Traffic = Existing Traffic + Growth in Existing Traffic + Approved Development Traffic); volume diagrams

o Background analysis with approved/funded highway projects. The effect of non-automobile modes (e.g. pedestrians, bicycles, transit) may be requested as well.

Projected Conditions, with site

o Traffic generated by the proposed development (i.e. site generated traffic) at build out, and/or at any significant phase/stage of development

o Total Traffic Analysis (Total Traffic = Existing + Growth + Approved Development + Site Generated); volume diagrams

o Analysis of total traffic with improvements. The effect of non-automobile improvements (e.g. pedestrians, bicycles, transit) may be requested as well.

Mitigation/Recommendations

o Discussion of analysis results

o If found to be needed, the consultant/developer should suggest improvements to mitigate the site traffic impacts, and provide analysis results of these mitigations.

Appendix

o All analysis and calculation work sheets, traffic related data, and pertinent correspondence (e.g. approved scope of work form)


Any operational modeling files (e.g. Synchro/SimTraffic, VISSIM files) used or developed for the Traffic Impact Study should be submitted electronically in conjunction with the report.

Existing, Background, and Projected Traffic ConditionsAll TIS reports should consider the traffic/trips generated under Existing, Background, and Projected conditions, as well as the operational impacts to the roadway study area for each of these conditions. Each report is to clearly include a section that discusses each condition.

Existing Conditions

Existing conditions represent current operations of the study intersections and roadway network identified for a TIS. For the purposes of the report, information such as intersection and roadway segment lane configurations, intersection controls, intersection and segment traffic volumes, major access points, and posted speed limits should be collected, and may be identified prior to any field review of the study area (to be used as needed for later operational analyses). Operational and safety issues, due to vehicular queuing or delay, driver or pedestrian behavior, geometric layouts, or other causes should be noted after performing a peak period (typically AM peak, PM peak, and/or midday peak) field review on a day(s) that is(are) representative of typical traffic within a study area. An operational analysis of existing conditions should be reported as part of this report section. A more in depth description of typical operational analysis procedures, and information to report, can be found in the Traffic Analysis/Network Evaluation section of these guidelines.

Growth in Existing Traffic

Growth in Existing traffic is described as a factor representative of travel increases through the study area associated with regional traffic growth. This factor should be applied to the existing through traffic, and appropriate turning movements, before Background (approved development, to be discussed subsequently) traffic is applied. A growth factor is usually applied to existing traffic if a development or phase of development is expected to reach build-out in excess of 3 years, measured from the time that traffic counts for the TIS were performed. Growth factors are not typically necessary to use when a development or phase of development is expected to reach build-out in 3 years or less.

Growth rates used in the study must be provided by and/or approved by MDOT-SHA’s Travel Forecasting and Analysis team and/or by the local agency during scoping.

Background Conditions

Background conditions reflect operations while considering Existing traffic, plus growth in existing traffic, plus approved development traffic. Approved development traffic is described as traffic generated by all approved developments within the study area at the time of the report preparation. Developments outside of the area are considered to be accounted for with the Growth in Existing Traffic (when used) noted above. These sites can be obtained from the local jurisdiction and should be documented in the TIS.


For large background developments with extended build out periods (5+ years), the effect of the full impact of the development on the roadway system may not be needed; however, the impact of this development, as it is expected to exist at the time of build-out of the proposed development, should be considered. Prior approval for background build-out assumptions are to be discussed with MDOT-SHA during scoping. An operational analysis of Background conditions should be reported. This analysis should take into consideration all transportation improvements expected to be in place within the study area by the proposed development’s build-out year. These improvements should include those which are already programmed or funded by the State or local jurisdiction. For any background development included in the TIS, its approved off-site road improvements should be included. Any improvement suggested as being implemented by “others” should indicate by whom. If funded by a public agency (e.g. the MDOT-SHA, the Consolidated Transportation Program (CTP) or local jurisdiction), then a copy of the page from the appropriate document should be included in the report. If funded by another developer, then documentation should likewise be included.

Projected Conditions

Projected conditions reflect operations while considering Background traffic, plus Site Traffic. Site traffic is described as traffic which will be generated by the proposed development, while Total traffic is the summation of Background traffic and site traffic. It is important to note that if the proposed site development is to be phased, earlier phases of the site development are not to be analyzed as “Background” generated trips for subsequent phase TISs. Site generated trips from earlier phases are to be considered as part of the total site trips generated for subsequent phase TISs.

After Total traffic is developed, an operational analysis of projected conditions is to be reported. This analysis should consider projected future roadway improvements in place (e.g. improvements addressed in the Background analysis).

Data Needs and ConsiderationsThe following information discusses, in more detail, typical data needs for the development of a TIS, as well as several considerations associated with data collection or inventory efforts.

Traffic Counts

Count Locations

Turning movement counts should be performed at each intersection to be analyzed, if current turning movement counts are not available.

13-hour turning movement counts should be performed at any intersection where it is anticipated that a new traffic signal may be needed.


Count Times/Days

Peak hour counts are acceptable at intersections, generally between 7-9 AM and 4-6 PM on Tuesdays, Wednesdays, or Thursdays. Expanded hours or different time periods may be determined as part of scoping (e.g. 11am - 2pm weekday or Saturday count at a shopping center) when the development would be expected to generate a significant level of traffic outside of the traditional weekday peak periods. All intersection counts should include pedestrian and bicycle counts as well.

Standard weekday counts should be taken on Tuesdays, Wednesdays, or Thursdays, and under normalized conditions (fair weather, limited to no roadway construction, etc.). Exceptions may be granted under appropriate limited circumstances, with justification (e.g. Friday PM peak summer traffic counts, weekend counts for shopping areas during the holiday season between Thanksgiving and Christmas, etc.).

Holiday Restrictions

Counts are not to be taken on or within 2 business days prior to, and 1 business day after, State or Federal holidays, with the exception of Christmas Day and New Year’s Day. Counts are not to be taken during the period beginning 5 business days prior to Christmas Day, through at least 1 business day after Martin Luther King, Jr. Day. Exceptions may be granted under appropriate limited circumstances, with justification (e.g. weekend counts for shopping areas prior to Christmas, etc.).

Presence of Schools

The presence of schools in the area should be considered when determining the date of counts. MDOT-SHA reserves the right to determine if counts should be taken while local schools are in session.

Limitations on Use of Older Data

Counts should generally not be more than 1 year old from the date of study publication. Counts between 1 and 2 years old may be used if factored to the current year. Counts older than 2 years will generally not be accepted. As part of scoping, updated traffic counts may be requested in locations where significant background development has been completed within the last 2 years, and/or where traffic volumes are expected to have varied significantly within the last 2 years.

The most recent traffic volume counts (generally within 2 years), whether by MDOT-SHA, consultant or local jurisdiction, may be used for the study, unless local conditions dictate that counts be taken during a specific period of the year (e.g. summer traffic counts on roadways significantly impacted by summer tourist traffic). Existing traffic counts performed by MDOT-SHA can be found through MDOT-SHA’s Internet Traffic Monitoring System (I-TMS) (http://maps.roads.maryland.gov/itms_public/).

Study locations where updated counts are needed, but current conditions exist such that these counts would not represent typical traffic volumes (e.g. ongoing construction near or within the study area), should be discussed with MDOT-SHA during scoping. MDOT-SHA can assist in determining a reasonable strategy for establishing representative traffic volumes.


http://maps.roads.maryland.gov/itms_public/

Other Traffic Data

Other existing traffic data to be collected may include queuing and travel time data (in the field), peak hour observations (AM, PM, and/or Midday), pedestrian, bicycle, and transit facilities inventory, signal timings, classified vehicular counts (e.g. for facilities with a high truck percentage), etc. These requirements need to be discussed during scoping for each individual project on a case-by-case basis.

All existing traffic data collected or obtained from any agency (e.g. queuing data, travel time data, peak hour observations, pedestrian, bicycle, and transit facilities data, signal timings, etc.) are to be included in the appendices of the TIS report.

Limitations on Use of Older Data

All existing traffic data collected or obtained from any agency (e.g. queuing data, travel time data, peak hour observations, pedestrian, bicycle, and transit facilities data, signal timings, etc.) will generally have a statute of limitations of two years from the time of collection or acquisition. In the rare case where a TIS does not reach the review stage and/or is not approved within the two year period, MDOT-SHA reserves the right to request updated data collection and analysis. MDOT-SHA also reserves the right to request updated data and analysis if significant development occurs within the study area that was not previously considered or was not previously open to traffic, or if geometric or operational changes to the roadway network were performed.

Trip Generation

Trip Generation Rates

Trip generation rates published by the local jurisdiction should be used, if available, for a TIS. In the absence of available local rates, the latest ITE Trip Generation Handbook fitted curve equations or average rates should be used. In the event ITE does not address the development land use type, or is of a limited sample size, studies of similar locations may be used. Documentation of these studies should be submitted for verification during scoping if conducted by the developer’s traffic consultant, and be included in the TIS report.

If using the latest ITE rates, ITE’s latest edition Trip Generation Handbook: An ITE Recommended Practice is to be used to estimate the appropriate trip generation for the proposed development site. Section 3.3 of the Handbook provides guiding principles for the approach to follow.

Trips Generated by Existing Development

Trips generated by an existing development may be excluded from consideration if the development was in use or occupied at the time traffic counts were performed. Such a scenario may apply to situations where an expansion of an existing development/site is being proposed.


Pass-by Trips

The latest ITE Trip Generation Handbook practices should be used to determine pass-by trips for background and site developments and/or internal trip capture for mixed use background and site developments. Publications such as the NCHRP 684 report also offer mixed use development guidance and can be used to determine internal trip capture.

TOD Consideration

MDOT-SHA is currently developing Transit Oriented Development (TOD) guidelines, including requirements for a TOD designation. A more definitive TOD standard is expected in the future. At this time, developers seeking to receive TOD credits will be considered on a case by case basis.

Trip Distribution Discussion of the assumptions behind the distribution of generated trips (both site and approved background development) should be provided. The methodology to be used should be discussed at scoping. Existing traffic distribution patterns may be considered for developments smaller in scope and size. For large-scale developments (those generating more than 750 peak hour trips), local MPO models, available County sub-area models, or MDOT-SHA’s statewide model may be used to identify site trip distribution percentages on roadways within the study area. In the case of large developments, MDOT-SHA will coordinate to assess whether this alternative trip distribution methodology is needed, or if MDOT-SHA can assist with a travel demand modeling effort.

Modal SplitDiscussion of mode choice assumptions (both site and approved background developments) should be provided. Rationalization should be based upon knowledge of the existing and future availability of programmed pedestrian or bicycle facilities and the local or regional public transportation system. MDOT-SHA will defer to local input if provided during scoping. In the absence of input from the jurisdiction, latest census information, local MPO data or GIS-based accessibility tools could be used to justify increased transit ridership or pedestrian/bicycle use.

Trip AssignmentTrips generated by the development site will be assigned to the roadway network based on the defined trip distribution and existing travel patterns. Trip assignments may be developed in accordance with existing travel patterns and capacity of the roadway network.

Trip assignment should consider the presence of all reasonable travel routes (e.g. routes with likely similar travel times) within the study shed.


Traffic Analysis/Network Evaluation

Analysis Tools

All intersections should be analyzed using the critical lane volume (CLV) technique and factors, if designated by the County/jurisdictional APFOs; however, CLV is a sketch level planning tool ideal for quick capacity calculations under isolated conditions. This technique can have drawbacks that make analysis using alternative tools necessary in many circumstances. The following are guidelines for use of Alternative tools for more detailed analysis.

Synchro/SimTraffic software (or a comparable macroscopic analysis and traffic microsimulation tool) is typically used to analyze all interrupted flow facilities (local streets, collectors, arterials, etc.). Existing calibrated Synchro/SimTraffic files developed by MDOT-SHA should be used when available.

SIDRA Intersection software is typically used to analyze roundabouts only; however, VISSIM software (or a comparable advanced traffic microsimulation tool) is typically used to analyze roundabouts that are in close proximity to adjacent intersections and/or have upstream or downstream operational impacts in the study network.

Highway Capacity Software (HCS) is typically used to analyze uninterrupted flow facilities (basic freeway segments, merge, diverge, and weaving segments); however, VISSIM (or a comparable advanced traffic microsimulation tool) is typically used to analyze uninterrupted flow facilities that are in close proximity to adjacent intersections and/or have upstream or downstream operational impacts in the study network. Existing calibrated VISSIM files developed by MDOT-SHA should be used when available.

o HCS is also used to analyze isolated intersections in rural areas.

In circumstances where an analysis tool or methodology exhibits the capability of evaluating operational and safety impacts due to non-motorized modes of travel (e.g. pedestrians and bicycles), MDOT-SHA reserves the right to request the traffic analysis to adequately incorporate these non-motorized impacts on study intersections and/or the study roadway network. Evaluation of non-motorized modes of travel should be discussed during scoping.

In special cases, after discussion during scoping, VISSIM (or a comparable advanced traffic microsimulation tool) analysis of the entire study network may be required.

In special cases where the development type is categorized as “Small,” per Table 1 above, it is likely that microsimulation analysis would not be necessary. Such scenarios and analysis requirements can be discussed during scoping.

Model Calibration

Synchro/SimTraffic

If a microsimulation model is used in the analysis, the model must be calibrated for existing conditions.


When available, MDOT-SHA microsimulation models can be used, and can be provided by MDOT-SHA.

o It is important to note that the study area from models provided by MDOT-SHA as a base may not directly overlap with the needs of the TIS.

o Further modification of these files on the part of the developer’s consultant may be required.

Common calibration requirements and techniques for the Synchro/SimTraffic software are provided below:

o In order to ensure a reasonable representation of traffic conditions that would be expected with a background and/or proposed development in place, it is necessary to first calibrate the Synchro/SimTraffic model to existing conditions for the AM, PM, and occasionally, weekend peaks.

o An existing Synchro file must be calibrated before any “Build” Synchro file can be created and analyzed.

o Common data needed for Synchro model calibration includes travel time runs (at least five runs per direction during the AM and PM peak periods on a typical traffic day, usually Tuesday, Wednesday, or Thursday), which provide observed conditions regarding vehicular speeds and delays throughout the corridor. Travel time runs must be taken for the mainline movement (typically through movements) along major roadways (e.g. MD, US routes) within the study area, and/or for additional movements. The extent of the travel time runs necessary, or if alternative methods/data can be used, can be discussed during scoping.

o Model seeding time must allow a vehicle to travel from one end of the network to the next; customary simulation seeding times span from 900 seconds (15 minutes) to 1,800 seconds (30 minutes). Longer seeding times may be considered for excessively large networks or high congestion. Recording time must be at least one hour for each peak, and must account for the peak hour factor.

o A minimum of 5 model runs must be completed before average outputs of all runs can be used for analysis. Additional runs may be necessary.

o Observations must also be made (preferably during the same day as the travel time runs, but as a separate effort) at each study intersection and along the study corridor that document vehicular queues for each turning movement.

Queues should be observed over a couple of signal cycles at least, and queue lengths should be recorded for each turning movement.

Noting where queues are excessive (e.g. spill out of the turning bays, extend beyond the turning bays and to an adjacent intersection) can provide valuable information when calibrating the microsimulation model.


o It must be determined whether or not adverse traffic operations (e.g. excessive queues, delays) that are known to occur outside of the study roadway network adversely affect operations within the Synchro study network.

If adverse outside operations do impact the roadway network, it is important to incorporate these impacts into the Synchro model; otherwise, the Synchro model developed may reflect conditions that are more optimistic than actually observed.

o Simulation travel time (from SimTraffic) should be within 10% or 30 seconds of observed travel time by roadway segment, by direction, and within 5% of overall observed travel time by corridor as a whole, by direction.

A roadway segment is typically defined as the section from one signalized intersection to an adjacent signalized intersection.

A roadway segment may be defined as a section of roadway up to approximately ½ mile in length if signalized intersections in a study corridor are located in close proximity to one another, such that it is impractical or infeasible to calibrate segments from one signal to a signal immediately adjacent.

Roadway segments are to begin and end at logical points (e.g. signalized intersections, ramp terminals, locations where there is a major source or sink in traffic volumes).

If additional data is available or collected that provides justification as to why the typical thresholds may not best reflect typical traffic conditions, it is possible that these calibration percentage thresholds may be adjusted on a case by case basis.

o Simulation turning movement queues must reasonably reflect queues observed in the field. This includes left, through, and right turn queues at every approach of every major intersection included in the Synchro roadway network.

o Vehicle Throughput/volumes produced in the microsimulation model runs should be within 10% of the count traffic volume. The comparison between volumes processed in the microsimulation and the actual traffic counts should be compared at intersections, as well as on ramps, when applicable.

VISSIM

Common calibration requirements and techniques for VISSIM microsimulation software are provided below:

o Two calibration approaches are used with all VISSIM models

Travel time and/or speed Vehicle throughput


o Seeding time must allow a car to travel from one end of the network to the next; customary simulation seeding times span from 900 seconds (15 minutes) to 1,800 seconds (30 minutes). Longer seeding times may be considered for excessively large networks or high congestion.

o A minimum of 5 runs must be completed before average outputs of all runs can be used for analysis. Additional runs may be necessary.

o Calibration of the network using travel times or speed must use short segment data, rather than overall corridor travel time/speed. A maximum of a ± 10 percent or ± 30 second variation is permitted for small segments no more than 1 mile long. Exceptions are permitted on a case by case basis with appropriate justification.

o For a facility spanning more than 1 mile, it is recommended to break the facility into segments based on obvious breakpoints (e.g. between signalized intersections, or at ramps). These new smaller segments would then be calibrated at ± 10 percent or ±30 second variation with an overall corridor calibration of ± 5 percent. On a facility longer than 1 mile without obvious breakpoints (e.g. between freeway ramps), ± 10 percent is considered appropriate.

o Vehicle Throughput/volumes produced in the microsimulation model runs should not exceed 10% of the count traffic volume. The comparison between volumes processed in the microsimulation and the actual traffic counts should be compared at intersections, as well as on ramps, when applicable.

Measures of Effectiveness/Results to Report

The following Measures of Effectiveness (MOEs) are to be reported, when applicable, for peak hours under the Existing Condition, Background Condition, and Projected (Total Traffic) Condition.

Level of Service (LOS), Delay, Volume to Capacity (v/c) Ratio

If using Synchro/SimTraffic software:

o Highway Capacity Manual (HCM) methodologies should be used to report Level of Service (LOS), intersection delay, and volume to capacity ratio for each study intersection, and for particular turning movements at each study intersection.

Synchro software provides an option to calculate LOS results based on HCM methodology.

If using VISSIM software:

o The node delay should be used to determine and report both overall intersection and individual turning movement delays, which can be converted into a LOS using HCM LOS threshold values.


Arterial LOS may be requested for major roadway segments, by direction, within the study area in certain circumstances (as discussed during scoping).

For diverge, merge, and/or weave areas, density and v/c ratio is used to determine LOS. If applicable to the study area, densities, v/c ratios, and corresponding LOSs for diverges, merges, and/or weaves are to be reported. HCM thresholds should be used for converting densities and v/c ratios into LOSs.

Queues

If using Synchro/SimTraffic software:

o 95th percentile queues for all turning movements at each study area intersection (using SimTraffic simulation outputs) are to be reported.

Please note that SimTraffic does not have the capability to directly report queue lengths that significantly exceed the link on which queues originate, or those that exceed available storage bays. Queues provided in the SimTraffic Queuing Report that appear to reach or slightly exceed the link or storage bay lengths (usually up to 75 feet greater than the link or storage bay) must be verified by observing the SimTraffic simulations to determine the actual queue length. An alternative methodology would involve gradually increasing the available storage bay length to determine the actual queuing demand. In the case of through queues, subsequent bend node queue lengths are to be added to the origin link reported queue lengths to determine the total queue.

o The available storage bay length for each study intersection turning movement is to be reported. If a double or triple lane storage bay is provided for a movement, report the length of each storage lane, not the total combined storage length of all lanes.

o Percent Blocking times for 95th percentile queues are to be reported (using SimTraffic outputs) in circumstances where 95th percentile queues for a particular turning movement block access to an adjacent travel lane (e.g. through queues blocking access to a right or left turn bay, left or right turn queues blocking access to a through lane).


o Maximum queue lengths for each turning movement (including through queues) of each study area intersection should be reported.

o The available storage bay length for each study intersection turning movement is to be reported. If a double or triple lane storage bay is provided for a movement, report the length of each storage lane, not the total combined storage length of all lanes.


Travel Times/Speeds


o Simulated travel times and speeds for each major roadway segment are to be reported. A major roadway segment typically consists of a section of roadway between two major signalized and/or unsignalized intersections.

General Considerations

The MOEs provided from the analysis tools (e.g. HCS, Synchro/SimTraffic, VISSIM, etc.) should be summarized, rather than only given in raw output form.

If microsimulation software tools are used to perform an analysis that involves signalized intersections, submission of existing signal timing phase diagrams (hard copy or digital) may be requested.

Any operational modeling files (e.g. Synchro/SimTraffic, VISSIM files) used or developed for the TIS must be submitted electronically in conjunction with the report.

If more than one analysis tool is used within a TIS, justification should be provided as to why the results from one tool were chosen over another, particularly if the chosen results yield a lesser operational impact to the roadway network.

Mitigation/RecommendationsThe following section discusses the information that is provided as part of the Mitigation/Recommendations of the TIS report, and establishes mitigation thresholds that ensure that the study area roadway operates as safely as possible with the presence of the proposed access. The traffic operational information and mitigation thresholds established in this section pertain to the alternative analysis methodology established during the scoping, NOT to the CLV methodology.

For all mitigation topics discussed subsequently, the intent of these guidelines is to ensure that a developer is only expected to mitigate the safety impacts of his/her own access, and is NOT required to mitigate the safety impacts of another development, or safety issues that would have existed without the proposed development in place.

Identification of Deficiencies/Mitigation Thresholds

After all applicable MOEs have been reported for the established study area for the TIS, intersection and roadway network deficiencies should be identified.

Counties/Jurisdictions with APFOs

For study areas in Counties/jurisdictions with APFOs, all study area intersections, intersection movements, and analyzed roadway segments shown not to meet the minimum overall LOS thresholds established by the County/jurisdiction APFO, are to be identified. Where needed,


mitigation is typically proposed as part of this report to meet County/jurisdiction APFO roadway adequacy LOS thresholds.

Counties/Jurisdictions without APFOs

For study areas in Counties/jurisdictions without APFOs, all study area intersections, intersection movements, and analyzed roadway segments shown not to meet the minimum overall “D” Level of Service under Existing, Background, and/or Projected (Total Traffic) conditions are to be identified. For roundabouts, entry lane movements with volume to capacity ratios exceeding 0.85 are to also be identified.

Mitigation may be proposed as part of this report, and is to improve overall intersections and analyzed roadway segments to the following LOS thresholds:

For intersections and roadway segments with a Background Condition of LOS ‘D’ or better, mitigation to LOS ‘D’ is needed.

For roundabouts with entry lane volume to capacity ratios of 0.85 or better under the Background Condition, mitigation of entry lane volume to capacity ratios of 0.85 is needed.

For intersections and roadway segments with a Background Condition of LOS ‘E’ or ‘F’, mitigation to the Background Condition LOS and associated delay is needed.

For roundabouts with entry lane volume to capacity ratios of 0.86 or worse under the Background Condition, mitigation of entry lane volume to capacity ratios of the Background Condition is needed.

All Locations

For study areas in all locations, the following deficiencies are to be identified:

Any 95th percentile [for SimTraffic (or similar) outputs] or Maximum [for VISSIM (or similar) outputs] study intersection turning movement queues (including through queues) that exceed available storage bays (e.g. turn lane lengths) or otherwise block access to major commercial and residential access points within the study area, due to the presence of the proposed development. MDOT-SHA may require additional mitigation if the total traffic resulting queues are perceived to present a safety concern for roadway users.

o If vehicle queues are fully contained within intersection storage bays under background conditions, the proposed development may be responsible for mitigation of any queues that cause vehicles to exceed that available storage. If queues under projected (total) conditions are able to be fully contained within the available storage, the developer is not responsible for any queue mitigation for the turning movement in question.

o If vehicle queues do not block access to major commercial or residential access points under background conditions, the proposed development may be responsible for mitigation of any queues that cause vehicles to extend beyond the access points. Mitigation of access point blockage typically would pertain to through movement queues.


Any diverge, merge, weave within the study are shown not to meet a minimum LOS of ‘D’ is to be identified. Mitigation to LOS ‘D’ is to be provided if the study indicates Background Conditions operate at LOS ‘D’ or better. Improvements proposed are to mitigate the impact of the proposed development if Background Conditions indicate a LOS ‘E’ or ‘F’.

o If the study area is located in a County/jurisdiction with an APFO that directly establishes mitigation thresholds for diverge, merge, and weave segments, those thresholds for mitigation may be used in lieu of the thresholds listed above.

Summary of Mitigation

Mitigation strategies that are recommended to address traffic safety deficiencies identified previously should be summarized in the TIS report. The summary should at least consist of a written description of any geometric, operational, and/or strategic improvements that are proposed by the applicant/applicant’s engineer. It should also include at least a concept level layout, along with some discussion of any obvious constraints, including right of way, structural, utilities, and environmental impacts.

A comparison showing how the recommended mitigation would address the operational and/or safety deficiencies identified as a result of the proposed development is to be included as well.

General Considerations

The following general considerations should be taken when identifying operational and/or safety deficiencies, and when mitigation is being recommended:

Pedestrian and Bicycle Access

Where appropriate, improvements should be proposed that will accommodate adequate pedestrian and bicycle access to the proposed development, as stated in COMAR Section 11.04.05. Requests for waivers of inclusion of bicycle and pedestrian facility improvements are subject to review and approval by MDOT-SHA.

Cooperative Mitigation

In circumstances where the impact of the proposed development or phased developments on roadway operations is expected to be minor, MDOT-SHA may request/allow the cooperation of one or several proposed developments in or near the study area to develop joint mitigation strategies that address the cumulative traffic operational impact of these developments.

Alternative Mitigation Strategies

In circumstances where required safety mitigation in the form of “traditional” roadway improvements (e.g. mainline roadway corridor widening) is not feasible or compatible with local jurisdiction strategic transportation plans (as determined by MDOT-SHA), MDOT-SHA reserves the right to consider alternative congestion mitigation strategies, such as Active Traffic Management and Intelligent Transportation Systems strategies, and/or non-motorized


improvement strategies. Alternative strategies will be considered by MDOT-SHA on a case-by-case basis.

Traffic Signal Warrant Analysis

If a traffic signal is to be proposed, then a signal warrant analysis must be performed in accordance with MDOT-SHA’s warrant analysis procedures, and be included in the report. Considerations such as turning phase analysis, special operations (e.g. flashing signals) and pedestrian and bicycle accommodations should be documented as well. After review of this analysis, MDOT-SHA may request additional study, including exploring other alternatives to signalization, before reaching a final determination as to the need for a signal. Meeting of a signal warrant(s) does not automatically guarantee MDOT-SHA approval of a new signal. All new traffic signal proposals (or other mitigation) must follow MDOT-SHA’s established approval procedures.


Appendix A: Sample TIS Scope of Work Form


MDOT-SHA Scope of Work Form: Traffic Impact StudiesProject Information and Details

Contact Information Name E-mail Address Telephone Number

ConsultantApplicant/DeveloperMDOT-SHA Liaison

Project Information

Project Name: Town/County:Project Location: (Attach area map depicting site location and study intersections)

Major Roadway with Proposed Access Point(s):

Minor/Other Roadway(s) with Proposed Access Point(s):

Project Description: (Provide details on land use, phasing, access location(s) and proposed number of access points, etc.)Proposed Development Use(s): (Check all that apply. Attach additional sheets if needed)

Residential ☐ Commercial ☐ Office ☐ Other ☐

Residential Use(s)Number of Units: _____________

ITE LU Code(s) or Local Trip Data:1: ___________ 2: ___________3: ___________ 4: ___________

___________Commercial Use(s)

ITE LU Code(s) or Local Trip Data:1: ___________ 2: ___________3: ___________ 4: ___________

Independent Trip Rate Variable:1: ___________ 2: ___________3: ___________ 4: ___________

Office Use(s)ITE LU Code(s) or Local Trip Data:1: ___________ 2: ___________3: ___________ 4: ___________


Other Use(s)ITE LU Code(s) or Local Trip Data:1: ___________ 2: ___________3: ___________ 4: ___________



Proposed Build Out Year (If phased, please list expected build-out year for each phase)

Total Peak Hour Development Trips (Greatest of weekday AM or PM, or midday weekend peaks)

50 – 100 ☐ 101 – 750 ☐ 750 or more ☐

Traffic Impact Study Details

Study Period:(If phased development, list Background and Future Years for each phase)

Existing Year: Future (Build-Out) Year(s):

Study Intersections (Attach additional sheets as necessary)

1. 6.

2. 7.

3. 8.

4. 9.

5. 10.

Traffic Data to Use (Specify SHA Counts, Consultant Counts, Count Location, etc.; attach additional sheets if necessary)

Traffic Count Date(s):

Peak Period(s) for Study: AM ☐ PM ☐ SAT ☐ Duration of Data Collection:

Annual Regional Vehicle Growth Rate:(Only provide if Build-Out is greater than 3 years in the future)

☐ _______ % ☐ Build-Out 3 years or less

Peak Period Analysis Hour(s):

Existing Pedestrian/Bicycle/Non-Auto Conditions(During study period(s))

No/Minor Presence ☐ Moderate Presence ☐ Major Presence ☐

Modes Accounted for in Analysis

Automobile ☐ Pedestrian ☐ Bicycle ☐ Transit ☐

Note: The effect of Pedestrian, Bicycle, and/or Transit modes should be accounted for when existing conditions indicate a major presence, and may be accounted for under a moderate presence.

Trip Adjustments Pass-by Trips: Yes ☐ No ☐

Reduction: ________% Trips

Internal Capture Trips: Yes ☐ No ☐

Reduction: ________% Trips


Trip Distribution (Describe percentage breakdown throughout study area)

Background Development Traffic Considered (List all developments included for analysis; attach additional sheets/map if necessary) Background/Planned Improvements Assumed(Include by whom)

Operational Analysis Methodology Synchro/SimTraffic ☐ HCS ☐ SIDRA ☐ VISSIM ☐ CLV ☐ Other (Specify) ☐

Additional Issues to be Addressed

Queuing analysis ☐ Merge/Diverge analysis ☐ Weaving Analysis ☐Pedestrian/Bicycle/Non-Auto ☐ TDM Measures ☐ Signal Coordination ☐

Traffic Signal Warrant Analysis Needed? Yes ☐ No ☐

Additional Notes:

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

SIGNATURE: ______________________________ DATE: _________________ Applicant/Consultant

PRINT NAME: ______________________________Applicant/Consultant


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