Modeling and Evaluating Bicycle Networks Based on Traffic Stress and Origin-Destination Connectivity

Transcription

1 Modeling and Evaluating Bicycle Networks Based on Traffic Stress and Origin-Destination Connectivity Maaza C Mekuria, Axum Design & Engineering Peter G Furth, Northeastern University Research sponsored by Mineta Transportation Institute, San Jose CA

2 What is the bicycle network? Is it all streets on which bicycling is legal, plus offstreet paths? Is it all streets with bicycle facilities, plus off-road paths?

3 But some bike facilities involve too much traffic stress for the mainstream population Bike lanes can be low-stress or high-stress 6 lanes, speed limit = 45 mph, bike lane disappears for cars to merge across to the right turn lane

4 Designated Bike Routes or shared streets can be low stress or high stress Bike boulevard on local street in Berkeley Signed Bike Route with speed limit = 35 mph, 4 lanes of heavy traffic, parked cars force bikes into shared lanes

5 and many untreated streets offer lowstress bicycling

6 Chief Deterrent to Bicycling = Traffic Stress Riders X 3 Low stress facility attracts high ridership X X 1 degree of traffic stress 6

7 First Priority: Connectivity Can you get from A to B: 1. safely (at a tolerable level of stress), and. without undue detour? OD Pair level: Which OD pairs are connected at a low level of stress? Which are connected only at a high level of stress? Network level: For a given level of stress, what fraction of OD-pairs are connected? GIS network image showing isolated neighborhood, obvious barrier

8 Classifying Links: Four Levels of Traffic Stress (LTS) 1. Suitable for 1-yr old. Low-stress consistent with Dutch guidelines 3. Medium-stress consistent with common US guidelines for basic cyclists 4. High stress serves traffictolerant riders only We developed our own criteria

9 Weakest Link Logic: Route stress = Stress of its most stressful link At what stress level are A and B connected? A Level 1: Not connected B Level : Connected, but with unacceptable detour Level 3: Connected without undue detour 1

10 Criteria for Shared Roads Roads without Centerline Markings Traffic volume (veh/day) up to 6000 up to 5500 up to 5000 up to 4500 up to 4000 up to 3500 up to 3000 up to 500 up to 000 up to 1500 up to 1000 up to 500 > 1 > > Speed Limit (mph) Roads with Centerline Markings > 1 > > Speed Limit (mph)

11 Criteria for Bike Lanes next to a Parking Lane Speed Limit < 5 mph 30 mph 35 mph > 40 mph LTS > 1 LTS > LTS > 3 LTS > 4 Street Width 1 thru lane + lanes per per direction direction LTS > 1 LTS > 3 Bicycling Space (bike lane + parking lane + buffer) > 15 ft In commercial areas: 14 to 14.5 ft In residential areas: 13 to 14.5 ft Otherwise LTS > 1 LTS > LTS > 3 Illegal Parking in the bike lane rare common LTS > 1 LTS > 3 Multiple criteria; worst score governs!

12 Stress level must account for intersection approaches Most of the block has a bike lane and one travel lane per direction but approaching a traffic signal, it widens to four lanes and the bike lane disappears

13 Also account for higher risk crossings A B Streets A and B have low traffic stress; but what about the stress in crossing from A to B?

14 Fields in the GIS street data Original data from the City s GIS: Curb-to-curb width Speed limit Road class (residential, arterial, ) Fields added using student labor: Number of lanes Presence of parking Bike lane s reach from the curb Right turn lane configuration

15 Calculating Link LTS

16 Subset of Links with LTS <

17 Travel Distance Tables for each LTS Travel Distance at Level of Traffic Stress 4 Travel Distance at Level of Traffic Stress 3 From \ To etc. Travel Distance at Level of Traffic Stress From \ To 1 Travel 3Distance 4 at etc. Level of Traffic Stress etc. From \ To etc. 1 From \ To etc etc. 4 etc. etc.

18 Acceptable Added Distance: Binary or Graduated A B Acceptable Added Distance (mi): Upper and Lower Bounds % acceptable 1.5 mi 1.0 mi % acceptable non-freeway automobile distance (mi)

19 Travel Distance Tables for each LTS Travel Distance at Level of Traffic Stress 4 Travel Distance at Level of Traffic Stress 3 From \ To etc. From \ To Travel 1 Distance 3at Level 4 of etc. Traffic Stress 1 Travel Distance at Level of Traffic Stress 1 1 From \ To etc. 1 From \ To etc etc. 3 etc. 4 4 etc. etc. Acceptable Added Distance (mi): Upper and Lower Bounds 0% acceptable 100% acceptable non-freeway automobile distance (mi) 1.5 mi 1.0 mi Allows us to answer: Is a particular OD pair connected at a given level of stress? Yes Partially No PairConnec tivity i j, LTS summarizes the result for each OD pair i-j (0 to 1)

20 Aggregating Over a Region to Evaluate City or Regional Network Geographical unit of analysis = Parcel Zip code, blockgroup are too big local access path is critical Parcel data is readily available from Assessor s Office Estimate productions and attractions for every parcel Productions: From population data at block level Allocate to parcels based on number of dwelling units Attractions: From employment data at zip code level Allocate to parcels based on ITE Trip Generation rates

21 Weight of a Parcel-Parcel Pair i-j Weight i-j = Propensity for Travel by Bicycle Productions i * Attractions j * Propensity i-j Distance (mi)

22 Network Evaluation: Fraction of OD Pairs Connected at each NetworkConnectivity Level of Traffic Stress LTS = Level of Traffic Stress Weight i j * PairConnectivity Hypothetical Result Weight i j Fraction of OD Pairs Connected 4 98% 3 % 8% 1 3% i j, LTS