February21st esp179-traffic


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  • This list is not exhaustive, other modes can include van pools, taxis, roller skates, wheelchairs. List can also be disaggregated (e.g. light rail, subway, commuter rail) or aggregated (e.g. auto, public, active)
  • - Different methods exist for calculating intersection LOS
  • In order to think about impacts on overall traffic, think about how many trips start and end at a place, as each trip, when added to everybody else’s single trips can result in trafficA “big place” or busy place (a big “attraction”) has lots of trips coming to and from itA smaller place, a smaller attraction may have less trips. However, something like a home, may have few people coming and going, but they may come and go several times
  • - The Trip Generation Manual, being produced by ITE, is an example of a non-governmental agency influencing calculation of impacts - The ITE is a professional organization, so in effect, the profession, using science and research, affecting policy- For example, specific land use codes exist for various types of residential (from detached housing, to small and large apartments, separate rates for rental homes/recreational homes), different types of parks/schools, commercial activities of many specific types (from supermarkets, to sporting goods stores, to bowling alleys)
  • Some quantitative measure is used for size of project (for shopping center its square feet, for other uses can be # of houses, # of hotel rooms, etc.). This is the X value of the regression equation with trips being the Y value.Fast food restaurant: R-square value of 7%... That’s not very good…There are a few thousand studies used to calculate ITE trip generation rates, so more common land uses have better data, but you can not necessarily follow them blindly
  • Adjust trip projections down based on amount of pass-by capture and on-site capture you think will happenThis determination of capture reductions is definitely a potential spot for professional disagreement
  • - Gravity model: Trips between an origin and destination are proportional of the size of attraction between the two places and inversely proportional to their distance
  • - Which routes people choose tend to be a function of distance (travel time), wait time, and cost
  • Synchro – Program used to analyze traffic, particularly easy to use for intersection LOSTransCAD – GIS based program to run travel models under different scenarios
  • Court case: West Sunnyvale Association vs. City Sunnyvale (2010). Must compare project impacts to existing condition. Road expansion project had initially compared future w/ project to future w/o project but not current
  • General consensus in transportation research that there can never be enough roads built to accommodate uninhibited demand for drivingThat’s not to say that we shouldn’t accommodate for cars as best as possible, however, sometimes maximum catering to cars can be counterproductive. First, it can’t completely solve vehicle congestion, and second, it makes alternatives less feasible.
  • Policies promoting active modes and public transit can exist in general plans/city ordinances that may conflict with by-the-book mitigation of automobile impactsPoint of alternative developments isn’t necessarily to exclude cars, but to make alternatives viable
  • - LOS classifications carry inherent positive/negative connotations, but do they really give travelers useful information? Are there
  • Parking spaces are expensive (10-50k per space)Parking spaces can take up a lot of space, which can discourage use of alternative modes, and present an opportunity cost in terms of space that could be used for other potentially economically productive usesEnvironmental impacts: parking lots are large impervious surfaces which have runoff and urban heat island effect issuesParking pricing: discourage driving by making it so that only people who are willing to pay/really need to drive parkParking pricing: encourage turnover of spaces --- having one car park all day for free in a prime location prevents other customers from using that space, and driving further economic activityParking sharing: let uses that don’t use parking at the same time to share spaces (e.g. an office park and a restaurant, or offices and shopping)Parking cash out: pay workers to not drive (to carpool or use alternatives) --- idea is to pay worker less than it would cost to build a parking space for that worker
  • - Having a warrant (or combination) of warrants tell you a device is warranted doesn’t automatically trigger the placement of a control device, but more so answers the theoretical what should be done in X case. Final placement of a device is more specific considering the context of the intersection
  • - Narrower streets preferred in smart growth projects for reasons including cumulative shorter distances between origins and destinations, slower vehicle speeds, less wear and tear on pavement
  • February21st esp179-traffic

    1. 1. Traffic andTransportationKevin FangESP 179 – Winter 2012University of California, Davis
    2. 2. 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 total 2
    3. 3. 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 3 • Method shortcomings, SB 375, parking…
    4. 4. Appendix G ChecklistXV. TRANSPORTATION/TRAFFIC -- Would the project:a) Cause an increase in traffic which is substantial in relation to r r r rthe existing traffic load and capacity of the street system (i.e., result ina substantial increase in either the number of vehicle trips, the volumeto capacity ratio on roads, or congestion at intersections)?b) Exceed, either individually or cumulatively, a level of service r r r rstandard established by the county congestion management agencyfor designated roads or highways?c) Result in a change in air traffic patterns, including either an r r r rincrease in traffic levels or a change in location that results insubstantial safety risks?d) Substantially increase hazards due to a design feature r r r r(e.g., sharp curves or dangerous intersections) or incompatible uses(e.g., farm equipment)?e) Result in inadequate emergency access? r r r rf) Result in inadequate parking capacity? r r r r 4g) Conflict with adopted policies, plans, or programs supporting r r r ralternative transportation (e.g., bus turnouts, bicycle racks)?
    5. 5. Transportation Basics 5
    6. 6. Transportation modesAUTOMOBILES Single-occupancy vehicles, carpools PUBLIC/MASS TRANSPORTATION 6ACTIVE MODES
    7. 7. 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
    8. 8. 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 8• Can also include pipelines
    9. 9. 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 Less vehicles, Lower speeds, More accessibility• Collector roads• Minor arterials• Major arterials 9• Freeways More vehicles, Higher speeds, More mobility
    10. 10. 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 10 • Ex: Local street ~600 vehicles per hour per lane
    11. 11. Measuring Auto Traffic, 2• Volume/capacity ratio (V/C ratio) • Volume of traffic on roads / capacity of road >1 Above capacity (congestion) 1 At capacity <1 Below capacity• Roadway Level of service (LOS) • A letter classification of amount of traffic on a road • Varies in how it can be measured (number of 11 vehicles/vehicle density, V/C ratio, speed, % of time spent following another vehicle)
    12. 12. C’s (and D’s) get degrees• DO NOT think about LOS as comparable to a school letter grade Speed A B C D E Speed-Flow F Curve Vehicle Throughput• You travel fastest @ LOS A 12• Lower LOS’ hold more traffic
    13. 13. Other Types of Level of Service Level of Vehicle Delay• Intersection Level of Service Service (sec/veh.) LOS A <10 • Average delay faced by a vehicle LOS B 10 – 20 approaching intersection LOS C 20 – 35 • Can be measured in terms of entire LOS D 35 – 55 intersection or individual turning LOS E 55 – 80 movement• Transit/bicyclist/pedestrian LOS • Point system based on network characteristics (e.g. presence of facilities, speed differential, 13 potential conflicts with others)
    14. 14. 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
    15. 15. AnalyzingTraffic Impacts 15
    16. 16. 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 16 • 3) Mode choice 4) Trip assignment
    17. 17. 4 Step Travel Demand Model 1) Trip generation • How many trips are being made? • Arguably, the most critical step Lots of people, Come/go once  lots of tripsFew people,Come/go a lot 17 lots of trips
    18. 18. 4 Step TravelDemand Model 1) Trip generation (cont)• Trip generation rates come from the Trip Generation Manual by the Institute of Transportation 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 18 given land use and its resulting trips
    19. 19. 4 Step TravelDemand ModelTripgenerationrate chart 19
    20. 20. 4 Step TravelDemand Model 1) Trip generation (cont)• Not all trips to a new development are “new” Development Empty Site New trips to site Existing trips passing by Pass-by capture – people stop at development who were already passing by 20 On-site capture – people who make multiple stops at a development on one trip/trips by people already there
    21. 21. 4 Step Travel Demand Model 2) Trip distribution • Where do those trips go?More trips go to/from Ex: Retail store willplaces that are large attract more trips from “attractions” highly populated areas 21 More trips go to places that are less distant (Gravity model)
    22. 22. 4 Step TravelDemand Model 3) Mode choice Suburban• Which mode will people Urban Rural use to make their trips to and from a site? Drive alone 72.1 81.5 84.8• Mode share typically Carpool 10.5 10.3 10.7 accounted at beginning Public 10.6 3.9 1.2 transp. • Ex: ITE Trip Generation rates are for vehicular traffic Walk 4.4 2.6 1.9 • Can do separate trip generation projections for All other 2.4 1.6 1.4 22 different modes 2009 Statistics Source: US Census (2011)
    23. 23. 4 Step TravelDemand Model 4) Trip assignment• What route will people choose to get to their destination? 23
    24. 24. Example of a 4-step process ←TRIP GENERATION Project proposal Produce X Retail: 635,200 sq. feet vehicular trips Office: 198,000 sq. feet (Mode choice) - Using trip gen. Hotel: 150 rooms rates minus capture Open space/park land 4% TRIP DISTRIBUTION→ Trips generated from project 24 distributed to different locations based on the attraction between them and the development
    25. 25. Example of a 4-step process↑ TRIP ASSIGNMENT ↑TRIP ASSIGNMENTNew trips from site to w/ MITIGATIONStheir destinationsassigned to roads inaddition to existingtraffic, compare to 25existing traffic INTERSECTIONS →*Sunnyvale case, 2010 Check intersection Level of Service
    26. 26. AdditionalConsiderations 26
    27. 27. 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 27 • Conflict with alternative transp. policies (question 15g)
    28. 28. 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
    29. 29. 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) 29 • Alternative, activity-based travel demand modeling (instead of trip-based, outside the box solution)
    30. 30. 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) 30
    31. 31. 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 31 • SCS is new component/element of Regional Transp. Plans • Transit priority projects
    32. 32. 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 32 terminal, or a bus line with 15-minute headways.
    33. 33. SB 375 CEQA Breaks, 3 Is this a categorical• Transit priority projects (cont.) or statutory exemption? • 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 CEQA consultant for a • 20% moderate income housing fully exempt transit priority project 33 • 10% low income housing • 5% very low income housing
    34. 34. 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 34 generation rates
    35. 35. Parking, 2• Lots of parking not always ideal • Is it an efficient use of resources? • Environmental impacts (runoff, UHI)• Parking mitigation strategies Pricing (SFPark) • Parking pricing (discourage driving/encourage turnover) • Sharing (day/night share spaces) • Mixing land uses (park once) • Cash out (pay workers to not drive) 35 Land-use mix and sharing (Surrey, BC)
    36. 36. 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 36
    37. 37. 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) 37
    38. 38. Emergency Access• Building codes commonly establish wide streets for emergency vehicle access• Smart Growth proponents prefer narrower streets • Village homes easement • Laguna west demonstration • Rounded curbs so emergency vehicle can roll up onto/ 38 straddle sidewalk
    39. 39. Questions 39