Multi-Modal Level of Service Toolkit
Person Delay
Overview Person delay uses microsimulation to evaluate the delay per person for each mode of travel at an intersection. The person delay for each mode can then be combined to create an overall person delay for the intersection. This method provides a better decision-making tool for developing improvements to facilitate more efficient movement of people, rather than a single mode, through an intersection. It also facilitates the development of multi-modal mitigation measures. It is useful for analyzing higher occupancy travel modes such as BRT or the influence of a grade-separated crossing, as it accounts for benefits or impacts to all facility users.
Description Conventional LOS approaches quantify the delay per automobile. Under the person-delay approach, impacts and mitigation measures are evaluated based upon the anticipated project impact to the delay at intersections for all users. This approach is based on the premise that, through simulation, enough data can be gathered to estimate the impact of additional traffic and/or physical changes to pedestrians, bicyclists, transit patrons, and motorists.
The shift to a per person delay calculation allows for an “apples to apples” comparison amongst the various modes and how modifications to the transport network affect each mode. Different improvements are anticipated to have differing affects on the delay of each mode and this methodology allows for a review of the effect on each mode and an aggregate calculation that compares the overall effects to the intersection.
Van Ness Avenue Bus Rapid Transit, San Francisco The SF County Transportation Authority developed a BRT proposal for Van Ness Avenue which intended to improve the corridor’s overall carrying capacity, reduce operating costs and passenger travel times, and reduce crossing distances for pedestrians. An evaluation of person throughput found that even if improved transit service did not attract more riders, taking lanes away from mixed traffic to create a BRT system would not reduce the corridor’s person carrying capacity. See Figure 1, right, for a VISSIM simulation of the proposed transit lanes in operation.
Figure 1: Simulation of BRT on Van Ness Avenue in San Francisco
Applications Development review
Transportation
Advantages
Corridor
Master Plans
Easy to compare across modes. Analogous to LOS measures of intersection delay, which practitioners already understand. Facilitates mitigations that benefit more people.
Studies
Mitigation
Testing
Disadvantages
More data intensive than traditional LOS. Delay may not be the best measure to describe conditions for pedestrians and bicyclists. May privilege auto mode in areas where SOV traffic predominates. try
Sample Applications Fehr & Peers has used Person Delay to evaluate proposed transportation developments in San Francisco and Davis, California. The UC Davis Campus Gateway project, pictured below (Figure 2), analyzed five alternatives using VISSIM micro-simulation software. Delay-based LOS for each mode (auto, bicycle, pedestrian and transit) was calculated along with air pollution impacts for each alternative. The analysis incorporated site-specific data from field observations, including measures of driver behavior and distributions of vehicle types. Evaluating multiple modes provided a detailed analysis of the modal tradeoffs between different alternatives. The VISSIM model was especially helpful as a communication tool with decision makers and members of the public.
Figure 2: UC Davis campus gateway: person delay measures multi-modal performance at an intersection
Software and time requirements This approach has utilized VISSIM to evaluate delay and develop visual representations of potential project-related changes. This requires approximately twice as much time to set up and operate as a model for a conventional analysis. Traffic counts that include bicycles and pedestrians take approximately 50% more time than auto-only counts.