Bicycle Level of Traffic Stress at Intersections

Project Description

To achieve societal goals in arenas as diverse as climate change, public health, safety, air quality, equity, livability, and competitiveness, many cities across the nation aim to promote bicycling as a means of mass transportation. This, in turn, requires an extensive and dense low-stress bicycling network. While some people can tolerate high levels of traffic stress, most people will consider using a bike only if there is a low-traffic-stress route from their origin to their destination.

Traffic stress can arise on links, but it can also arise at intersections. However, in current practice, Level of Traffic Stress (LTS) analysis typically considers only traffic stress along links. If LTS does consider intersections, it often does so inadequately.

There are two knowledge gaps preventing intersections from being properly accounted for. One is that published criteria for LTS at intersections, which have not changed since LTS criteria were first published in 2012 (Mekuria, Furth, and Nixon, 2012), are meager and only account for the traffic stress involved in pocket bike lanes and multilane, unsignalized crossings. They fail to account for many other factors that may make intersections and crossings a barrier to cycling for many people.

The second is that known methods for bike network analysis are based on link-level stress and costs (i.e., distance); their structure is such that they do not recognize stress or cost at nodes. The seminal work on LTS (Mekuria, Furth, and Nixon, 2012) suggested a workaround, applying intersection crossing stress to the links approaching an intersection; however, that workaround has limitations that will distort results in many situations. For example, consider approaching a busy road with a cycle track. There may be high stress in crossing that street, but no stress in turning right onto the cycle track; this dichotomy cannot be resolved by applying the crossing stress to the approach link. This research will involve the following four tasks:

1. Develop a comprehensive set of criteria for level of traffic stress at intersections. It should account for factors that create stress on an intersection approach (e.g., pocket bike lanes) as well as factors that create stress when passing through an intersection. For the latter, there should be a way to determine level of traffic stress by movement; for example, from a given approach, there might be little or no traffic stress to make a right turn, a moderate traffic stress to go through, and high traffic stress to make a left turn.

2. Develop an algorithm and needed data structures to do network analysis accounting for traffic stress at intersections as well as on links and create open-source code on standard platforms that will allow others to apply these algorithms.

3. Collect data for two cities. One city may be Albuquerque and the other may be a city for which the research team already has link-level LTS data.

4. Apply LTS criteria for both links and intersections and use the developed algorithms to do connectivity and accessibility analyses. These analyses will serve both to test the newly developed intersection LTS criteria and to test the newly developed network analysis algorithms.