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Publication Number: FHWA-HRT-06-130
Date: April 2007

Pedestrian and Bicyclist Intersection Safety Indices

User Guide

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CHAPTER 1. OVERVIEW

What are the Pedestrian and Bicycle Intersection Safety Indices?

The Pedestrian and Bicycle Intersection Safety Indices (Ped ISI and Bike ISI) are a set of models that enable users to identify intersection crossings and intersection approach legs that should be the greatest priority for undergoing pedestrian and bicycle safety improvements. Using observable characteristics of an intersection crossing or approach leg, the tool produces a safety index score, with higher scores indicating a greater priority for an indepth safety assessment. Each leg of an intersection may have different characteristics affecting pedestrian or bicyclist safety; therefore the tools are intended to provide an evaluation of the safety of an individual crossing (Ped ISI) or approach leg (Bike ISI) rather than evaluating the intersection as a whole. A practitioner can use the tool to develop a prioritization scheme for a group of pedestrian crossings or bicyclist approaches. This method enables the practitioner to prioritize and proactively address sites that are the most likely to be a safety concern for pedestrians or bicyclists.

Why are Ped ISI and Bike ISI needed?

The need to address pedestrian and bicyclist safety is ever present. National crash statistics for 2004 show that 4,641 pedestrians and 725 pedalcyclists were killed in crashes, accounting for approximately 13 percent of all traffic fatalities in the United States.(1) Most of these crashes occur at intersections. Many States and municipalities have pedestrian and bicycle safety programs to identify and address high crash locations. Although these safety programs can treat pedestrian or bicyclist hazards as they are identified, it would be preferable to use a proactive method of prioritizing which intersections should be examined first to ensure that potentially risky locations are addressed before they become crash problems.

What are the benefits of Ped ISI and Bike ISI?

Ped ISI and Bike ISI proactively prioritize pedestrian crossings and bicyclist approaches with respect to safety. They also provide forward–looking State and local planning agencies with a safety rating tool for proposed intersections. Each tool uses observable and easy–to–gather data.

Where can Ped ISI and Bike ISI be used?

Ped ISI and Bike ISI were developed at urban and suburban intersections with the following characteristics:

  • Three–leg and four–leg intersections.
  • Signalized, two–way stop, and four–way stop.
  • Traffic volumes from 600 to 50,000 vehicles per day.
  • One–way and two–way roads.
  • One to four through lanes.
  • Speed limits from 24.1 to 72.4 kilometers per hour (km/h) (15 to 45 miles per hour (mi/h)).

Ped ISI and Bike ISI are used most appropriately at intersections that meet the above ranges. Safety index values produced for intersections with characteristics outside these ranges should be used only with the understanding that the models were not developed using intersections of that type.

Steps for using the Ped ISI and Bike ISI

  1. Select Sites To Evaluate—Identify pedestrian crossings (Ped ISI) or intersection approaches (Bike ISI) to evaluate. It is not necessary to evaluate all intersections in a given locality at once, especially where there is a large number of sites. Here are some useful tips for considering how to begin selecting sites:
    • Are there sites in the planning stage that could be modified in the design phase to avoid potential problems?
    • Is there an area where there may be moderate to high pedestrian and/or bicyclist activity, such as in a central business district or near a popular pedestrian or bicyclist attractor?
    • Are there sites that have already been identified in the community (including residents or other users) as possible problems?
    • Are there sites where a crash has occurred? Typically these tend to naturally receive focused attention, but it may also prove useful to develop a safety index score to provide perspective, or to help identify what factor(s) may be affecting safety.
  2. Gather Data—Gather data on geometric and operational characteristics of the selected sites, either through electronic databases or brief field visits. If the sites are in the planning stages, determine what characteristics the sites are expected to have. See the list of data required for the safety indices on page 7. A sample data collection form is available in Appendix A.

  3. Calculate Index Values—Use Ped ISI and Bike ISI to produce index values for each site. Each site will receive a safety index value between 1 (safest) and 6 (least safe). The Ped ISI equation is shown on page 8; the Bike ISI equation is shown on page 11. Example calculations of index values are found starting on page 20. Users may also opt to use the Quick Reference Tables found in Appendix B to determine safety index values when a computer is not available.

  4. Prioritize Sites—Sort sites according to index values. Sites with the highest index values generally have the highest priority for further indepth evaluation of pedestrian and/or bicycle safety. However, the existence of a high Ped ISI or Bike ISI value does not mean that a crosswalk or intersection approach is necessarily "hazardous." There are many characteristics and behaviors at an intersection that will result in a pedestrian or bike crash, and no method can include all of these factors. Knowledge of the area should also be used in the prioritization of sites. The Ped ISI/Bike ISI method merely provides a way to prioritize locations to identify those which may warrant more indepth study.

FHWA–HRT–06–130

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