TECHBRIEF Pedestrian and Bicyclist 

Intersection Safety Indices

Publication No. FHWA-HRT-06-129

FHWA Contact: Ann Do, HRDS-06, 202–493–3319, 

ann.do@fhwa.dot.gov

Overview

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 indepth 

pedestrian and bicycle safety assessment. Using observable 

characteristics of an intersection crossing or approach leg, such 

as number of lanes and traffic volume, the tool produces a safety 

index score, with higher scores indicating greater priority for an

indepth safety assessment. Each leg of an intersection may

have different characteristics affecting pedestrian or bicyclist 

safety; therefore, the tool is intended to provide a rating 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 without having to wait for crashes 

to occur. 

Development

Researchers developed the Ped ISI and Bike ISI based on safety 

ratings, or expert opinion of the safety of a site, and observed 

behaviors, or observed interactions between pedestrians and 

motorists or bicyclists and motorists. These measures enabled 

the researchers to use a multifaceted approach to determine the 

relative safety of a pedestrian crossing or bicycle approach leg. 

To develop the Ped ISI and Bike ISI models, researchers studied 

68 pedestrian crossings at signalized and unsignalized intersections in Miami, FL, Philadelphia, PA, and San Jose, CA, and 

67 bicycle approaches at signalized and unsignalized intersections in Eugene, OR, Gainesville, FL, Philadelphia, PA, and 

Portland, OR. 

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.tfhrc.gov
Safety Measure: Ratings

To develop the safety ratings, evaluators 

knowledgeable about pedestrian and bicyclist 

issues viewed illustrations and videos of the 

pedestrian crossings and bicycle approaches, 

as shown in figure 1, and rated the sites according to their perceived level of safety for a 

pedestrian or bicyclist. Researchers asked the 

evaluators to view the illustration and video as 

if they themselves were pedestrians crossing 

at the crosswalk or bicyclists approaching the 

intersection. The evaluators then rated the sites 

on a scale of one (most safe) to six (least safe), 

according to their sense of safety and comfort. 

Safety Measure: Observed Behaviors 

At Intersections

To evaluate observed behaviors, researchers 

videotaped each site and watched the tapes to 

record the behavior of pedestrians and bicyclists 

when they interacted with motorists. Recorded 

behaviors included changes in speed or direction 

by a pedestrian, bicyclist, or motorist in response 

to the presence of another party. The researchers, for example, would record instances when 

a pedestrian stopped before or during a crossing because of an oncoming vehicle or when a 

right-turning vehicle slowed down or stopped 

to avoid a bicyclist. These interactions included 

avoidance maneuvers (any change in speed or 

direction) and conflicts (sudden change in speed 

or direction). In total, the researchers observed 

1,898 bicyclist-motorist interactions and 1,095 

pedestrian-motorist interactions.

Ped ISI

As shown in table 1, the Ped ISI model consists 

of one equation that determines the safety index 

score for a single pedestrian crossing. 

Figure 1. An example of an illustration and a screen 

capture from the video shown to evaluators. 

Ped ISI = 2.372 – 1.867SIGNAL – 1.807STOP

+ 0.335THRULNS + 0.018SPEED + 

0.006(MAINADT*SIGNAL) + 0.238COMM

where:

Ped ISI Safety index value 

SIGNAL Signal-controlled 

crossing

0 = no

1 = yes

STOP Stop-sign-controlled 

crossing

0 = no

1 = yes

THRULNS Number of through 

lanes on street 

being crossed (both 

directions)

1, 2, 3,...

SPEED 85th percentile 

speed of street being 

crossed

Speed (miles per 

hours (mph))

MAINADT Main street traffic 

volume

Average Daily 

Traffic (ADT) (in 

thousands)

COMM Predominant land 

use in surrounding 

area is commercial 

development (i.e., 

retail, restaurants)

0 = not 

predominantly 

commercial area

1 = predominantly 

commercial area

Table 1. The Ped ISI model is shown.
Bike ISI 

As shown in table 2, the Bike ISI consists of three 

equations. Each equation determines the safety 

index score for a single bicycle movement, either 

straight through, left turn, or right turn. 

Table 2. The Bike ISI model is shown.

Through

Bike ISI = 1.13 + 0.019MAINADT + 0.815MAINHISPD + 

0.650TURNVEH + 0.470(RTLANES*BL) + 0.023(CROSSADT*NOBL) + 

0.428(SIGNAL*NOBL) + 0.200PARKING

Right Turn Bike ISI = 1.02 + 0.027MAINADT + 0.519RTCROSS + 0.151CROSSLNS + 

0.200PARKING

Left Turn Bike ISI = 1.100 + 0.025MAINADT + 0.836BL + 0.485SIGNAL + 

0.736(MAINHISPD*BL) + 0.380(LTCROSS*NOBL) + 0.200PARKING

where:

Bike ISI Safety index value

BL Bike lane presence 0 = NONE or Wide Curb Lane (WCL)

1 = Bike Lane (BL) or Bike Lane 

Crossover (BLX)

CROSSADT Cross street traffic volume ADT (in thousands)

CROSSLNS Number of through lanes on cross 

street

1, 2,...

LTCROSS Number of traffic lanes for cyclists 

to cross to make a left turn

0, 1, 2,...

MAINADT Main street traffic volume ADT (in thousands)

MAINHISPD Main street speed limit ≥ 35 mph 0 = no

1 = yes

NOBL No bike lane present 0 = BL or BLX

1 = NONE or WCL

PARKING Onstreet parking on main street 

approach

0 = no

1 = yes

RTCROSS Number of traffic lanes for cyclists 

to cross to make a right turn

0, 1, 2,...

RTLANES Number of right turn traffic lanes 

on main street approach

0, 1, 2,...

SIGNAL Traffic signal at intersection 0 = no

1 = yes

TURNVEH Presence of turning vehicle traffic 

across the path of through cyclists

0 = no

1 = yes

User Guide

The Pedestrian and Bicyclist Intersection Safety 

Indices: User Guide (FHWA-HRT-06-130) is a 

companion document to the research report 

that provides the practitioner the information 

needed to implement the Ped ISI and Bike ISI. It 

covers the data needs, presents the models, and 

provides examples of how to use the Ped ISI and 

Bike ISI. It also includes quick reference tables, 
Researcher—This study was performed by the University of North Carolina Highway Safety Research 

Center, Chapel Hill, NC. 

Distribution—This TechBrief is being distributed according to a standard distribution. Direct distribution 

is being made to the Divisions and Resource Center.

Availability—The publication from which this TechBrief was developed, Pedestrian and Bicyclist 

Intersection Safety Indices: Final Report, (FHWA-HRT-06-125), will be available from the National 

Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. A limited number of copies 

will be available from the Research and Technology Product Distribution Center, HRTS-03, FHWA, 9701 

Philadelphia Court, Unit Q, Lanham, MD 20706, 301–577–0818 (telephone), 301–577–1421 (fax). 

Key Words—pedestrian, bicycle, intersection, safety, index

Notice—This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for the use of the 

information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered 

essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides high-quality 

information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity 

of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to 

ensure continuous quality improvement.

April 2007 FHWA-HRT-06-129

HRDS-06/4-07(1M)E

such as the one shown in figure 2, that enable 

users to determine a safety index value for a site 

without the need for a calculator or computer. 

For more details on the underlying research and 

model development, see the final research report:

Carter, Daniel L., William W. Hunter, Charles V. 

Zegeer, J. Richard Stewart, and Herman F. Huang, 

Pedestrian and Bicyclist Intersection Safety Indices: 

Final Report, Federal Highway Administration, 

Washington, DC, Report FHWA-HRT-06-125, 2006.

Figure 2. An example of a quick reference table found in the User Guide.