Traffic and TransportationKevin FangESP 179 – Winter 2012University of California, Davis

Midterm• Will be graded out of 60 questions rather than 65• 54 = A-• 48 = B-• 42 = C-• 36 = D-• 30 = F

• Total score is the black score under total• Red marks/total may not total black score due to lower

accuracy of red machine. Higher black score is total2

Outline• 1) Appendix G Checklist

• 2) Transportation Basics• Terms and Lingo

• 3) Analyzing Traffic Impacts of a Project• The Traffic Impact Study

• 4) Additional Considerations• Method shortcomings, SB 375, parking…

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Appendix G ChecklistXV. TRANSPORTATION/TRAFFIC -- Would the project: a) Cause an increase in traffic which is substantial in relation to the existing traffic load and capacity of the street system (i.e., result in a substantial increase in either the number of vehicle trips, the volume to capacity ratio on roads, or congestion at intersections)?

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b) Exceed, either individually or cumulatively, a level of service standard established by the county congestion management agency for designated roads or highways?

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c) Result in a change in air traffic patterns, including either an increase in traffic levels or a change in location that results in substantial safety risks?

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d) Substantially increase hazards due to a design feature (e.g., sharp curves or dangerous intersections) or incompatible uses (e.g., farm equipment)?

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e) Result in inadequate emergency access?

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f) Result in inadequate parking capacity? r

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g) Conflict with adopted policies, plans, or programs supporting alternative transportation (e.g., bus turnouts, bicycle racks)?

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TransportationBasics

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Transportation modes

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AUTOMOBILES Single-occupancy vehicles, carpools

ACTIVE MODES

PUBLIC/MASS TRANSPORTATION

Types of passenger trips• Common types of trips:• Work trips• Shopping trips• Social/recreational trips• School trips• Home-based trips• of any other trip type

• Type of trip important as their characteristics vary (who, when, trip consistency) 7

Cargo travel• Trucks travel ~250 billion miles/year• 8% of CO2 , 50% of NOX, 40% of PM (US emissions)

• 4 main cargo modes• Truck• Train• Ship• Air

• Can also includepipelines

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Types of roads• Important in the context of capacity, amount of

traffic expected on a road, who uses it, who might be interested in traffic on them, etc.

Some main types of roads• Local streets• Collector roads• Minor arterials• Major arterials• Freeways

Less vehicles, Lower speeds, More accessibility

More vehicles, Higher speeds, More mobility

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Measuring Auto Traffic, 1• Number of vehicles/traffic volume• Traffic counts/roadway sensors• Various time scales (daily, hourly, etc.)• Often look at Peak Hour traffic (vs. avg.)• Can also express traffic volume in terms

of traffic density (e.g. 20 cars/lane mile)

• Roadway capacity• Often expressed in terms of vehicles/hour/lane• Ex: Freeway ~ 2,000 vehicles per hour per lane• Ex: Local street ~600 vehicles per hour per lane

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• Volume/capacity ratio (V/C ratio)• Volume of traffic on roads / capacity of road

• Roadway Level of service (LOS)• A letter classification of amount of traffic on a road• Varies in how it can be measured (number of

vehicles/vehicle density, V/C ratio, speed, % of time spent following another vehicle)

Measuring Auto Traffic, 2

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>1 Above capacity (congestion)

1 At capacity

<1 Below capacity

C’s (and D’s) get degrees• DO NOT think about LOS as

comparable to a school letter grade

• You travel fastest @ LOS A• Lower LOS’ hold more traffic

Spee

d

Vehicle Throughput

AB

C

D

E

F

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Speed-Flow Curve

Other Types of Level of Service• Intersection Level of Service• Average delay faced by a vehicle

approaching intersection• Can be measured in terms of entire

intersection or individual turning movement

• Transit/bicyclist/pedestrian LOS• Point system based on network

characteristics (e.g. presence of facilities, speed differential, potential conflicts with others)

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Level of Service

Vehicle Delay(sec/veh.)

LOS A <10

LOS B 10 – 20

LOS C 20 – 35

LOS D 35 – 55

LOS E 55 – 80

Highway Capacity Manual

• Published by the Transportation Research Board (TRB)

• Contains concepts, figures, procedures to assist in calculating capacities/ evaluating quality of operations of transportation facilities 14

AnalyzingTraffic Impacts

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Traffic Impact Study• Analysis of traffic impacts of a project by

comparing road conditions prior to project and projected conditions after project• Common standard threshold of 100 peak hour trips to

trigger completion of a full traffic impact study• Less trips can trigger TIS if existing LOS is poor

• Conventionally, new trips are projected by applying the 4-step travel demand model• 1) Trip generation ● 2) Trip distribution• 3) Mode choice ● 4) Trip assignment

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1) Trip generation• How many trips are being made?• Arguably, the most critical step

4 Step Travel Demand Model

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Lots of people,Come/go once lots of trips

Few people,Come/go a lot lots of trips

1) Trip generation (cont)• Trip generation rates come

from the Trip GenerationManual by the Institute ofTransportation Engineers (ITE)

• Different rates available for many specific land uses (~100 codes)• Land use codes correspond to manual entries• Rates are determined by regressing number of trips vs.

project size from “multiple” empirical studies on a given land use and its resulting trips

4 Step Travel Demand Model

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Tripgenerationrate chart

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4 Step Travel Demand Model

• Not all trips to a new development are “new”

● Pass-by capture – people stop at development who were already passing by● On-site capture – people who make multiple stops at a development on one trip/trips by people already there

Empty SiteDevelopment

1) Trip generation (cont)4 Step Travel Demand Model

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Existing trips

passing by

New trips to site

2) Trip distribution• Where do those trips go?

4 Step Travel Demand Model

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More trips go to/from places that are large

“attractions”

Ex: Retail store will attract more trips from highly populated areas

More trips go to places that are less distant (Gravity model)

3) Mode choice• Which mode will people

use to make their trips to and from a site?

• Mode share typically accounted at beginning• Ex: ITE Trip Generation rates

are for vehicular traffic• Can do separate trip

generation projections for different modes

4 Step Travel Demand Model

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Urban

Suburban Rural

Drive alone 72.1 81.5 84.8

Carpool 10.5 10.3 10.7

Public transp. 10.6 3.9 1.2

Walk 4.4 2.6 1.9

All other 2.4 1.6 1.4

2009 StatisticsSource: US Census (2011)

4) Trip assignment• What route will people choose to get to their

destination?

4 Step Travel Demand Model

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Example of a 4-step process

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←TRIP GENERATIONProject proposalRetail: 635,200 sq. feetOffice: 198,000 sq. feetHotel: 150 roomsOpen space/park land

TRIP DISTRIBUTION→Trips generated from project

distributed to different locations based on the attraction between

them and the development

2%

3%

2%

4%

1%

Produce X vehicular trips(Mode choice)- Using trip gen. rates minus capture

Example of a 4-step process

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↑ TRIP ASSIGNMENTNew trips from site to their destinations assigned to roads in addition to existing traffic, compare to existing traffic *Sunnyvale case, 2010

INTERSECTIONS →Check intersection

Level of Service

↑TRIP ASSIGNMENT w/ MITIGATIONS

AdditionalConsiderations

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Limitations of traffic analysis• Analytical process/methods are very car-centric• Strict application of methods and their outputs can

codify automobile-centricity• First instinct when faced with projected new car trips

is to build more capacity

• Problems with over-capacity• Induced travel demand• Decreased feasibility of

alternatives• Conflict with alternative

transp. policies (question 15g)

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Compact development• Newer movements in land

development • Smart growth, compact development,

transit-oriented development• Oriented for increased feasibility of

public transit/active travel modes• More compact development/greater

mix of land uses bring origins and destinations closer together• Denser development where transit

service is present 28

Alternative trip generation rates• Existing trip generation rates (based on studies

of existing development) do not necessarily know how to project trip rates for compact dev.

• Current research focused on• Alternative trip generation rates for smart growth

projects (inside the box solution)

• Alternative, activity-based travel demand modeling (instead of trip-based, outside the box solution)

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Alternative performance measures

• 95th percentile travel time• Maximum travel time 95% of time

• Buffer index• Add X% of time to plans to be sure you will usually make it

• Mitigation measures can focus on making travel more reliable (but not necessarily less total travel)

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SB 375 CEQA Breaks, 1• SB 375 – Sustainable Communities and Climate

Protection Act of 2008• Goal to reduce GHG emissions from passenger vehicles• Some of this reduction to come from promoting less

driving/increased use of alternatives• Compact development/TOD facilitates alternatives

• SB 375 CEQA breaks for• Residential or mixed-use projects consistent with

regional Sustainable Communities Strategy• SCS is new component/element of Regional Transp. Plans

• Transit priority projects

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SB 375 CEQA Breaks, 2• Residential/mixed-use consistent with SCS• CEQA streamlining• Does not have to cover growth-inducing impacts,

project-specific and cumulative climate change impacts

• Transit-priority projects• 1) Contain at least 50% residential use• 2) Have a minimum net density of 20 units per acre• 3) Commercial portion of project floor-area ratio of 0.75• 4) Be located within ½ mile of either a rail stop, a ferry

terminal, or a bus line with 15-minute headways.32

SB 375 CEQA Breaks, 3• Transit priority projects (cont.)• Streamlining or full CEQA exemption if• They are no bigger than 8 acres or 200 units• They can be served by existing utilities• They will not have a significant effect on

historic resources• Their buildings exceed energy efficiency

standards• They provide ANY of the following:• 5 acres of open space• 20% moderate income housing• 10% low income housing• 5% very low income housing

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CEQA consultant for a fully exempt transit priority project

Is this a categorical or statutory exemption?

Parking, 1• Two types of parking spaces: on-

street and off-street parking spaces

• Zoning codes also typically delineate required number of spaces required• Ex: X spaces per Y sq. ft. of retail, W

uncovered & Z covered spaces per house• Ex: Often written to hold peak demand

• ITE also produce parking trip generation rates

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Parking, 2• Lots of parking not always ideal• Is it an efficient use of resources?• Environmental impacts (runoff, UHI)

• Parking mitigation strategies• Parking pricing (discourage

driving/encourage turnover)• Sharing (day/night share spaces)• Mixing land uses (park once)• Cash out (pay workers to not drive)

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Pricing (SFPark)

Land-use mix and sharing (Surrey, BC)

Warrant analysis, 1• Determination of whether an intersection

requires a traffic control device• Stop sign• Stop light• Interchange• No control

• Fewer stop signs/lights on roads with low AND high traffic

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Warrant analysis, 2• Criteria (8 “warrants”) to evaluate what device is

appropriate is set by the Manual on Uniform Traffic Control Devices (MUTCD) set by the Federal Highway Administration (FHWA)

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Emergency Access• Building codes commonly

establish wide streets for emergency vehicle access

• Smart Growth proponentsprefer narrower streets• Village homes easement• Laguna west demonstration• Rounded curbs so emergency

vehicle can roll up onto/ straddle sidewalk

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Questions

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