City of Seattle, WA, USA, Crosswalk Inventory and Improvement Plan, The

Institute of Transportation Engineers. ITE Journal, Jan 2004 by Hefferan, Jennifer R, Lagerwey, Peter

THE CITY OF SEATTLE, WA, USA, COMPLETED A COMPREHENSIVE INVENTORY OF MARKED CROSSWALKS AT UNCONTROLLED LOCATIONS. RATHER THAN USING THE INVENTORY TO REMOVE UNSAFE CROSSWALKS, IT WAS SEEN AS A MEANS TO IDENTIFY CROSSWALKS WITH SAFETY PROBLEMS AND FIND WAYS TO HELP PEDESTRIANS CROSS THE STREET. THE RESULT WAS A PLAN FOR PEDESTRIAN SAFETY IMPROVEMENTS AT MARKED CROSSWALKS.

BACKGROUND

In 2001, each of the approximately 850 uncontrolled marked crosswalks in Seattle, WA, USA, was systematically evaluated and inventoried. The collected data have been used to implement crosswalk improvements. This process, which has been easy to complete, has resulted in substantial improvements in pedestrian safety at uncontrolled marked crosswalks throughout the city.

The following case study summarizes the rationale, tools and methodology used in the City of Seattle's marked crosswalk inventory and resulting improvement plan. It is hoped that this information will encourage other jurisdictions to conduct similar projects and improve pedestrian safety at crosswalks in their communities.

Although crosswalks are a key component of the transportation system, both drivers and pedestrians frequently misunderstand them. In simple terms, a legal crosswalk exists where two streets intersect or, in the absence of an intersection, where a crosswalk is designated with markings. Thus, there are two types of crosswalks: marked and unmarked.

Marked crosswalks are useful traffic devices because they alert drivers to locations where pedestrians should be expected and show pedestrians a preferred place to cross the road. Crosswalks often are marked in locations controlled by traffic signals or stop signs (controlled locations) or in locations where traffic is not controlled by signals or stop signs (uncontrolled locations).

THE BASIS FOR THE CROSSWALK PLAN

In 2001, the City of Seattle began a process to demonstrate that the recommendations developed in the study, "Safety Effects of Marked vs. Unmarked Crosswalks at Uncontrolled Locations," by Zegeer, Stewart, Huang and Lagerwey, could be used as part of a comprehensive effort to improve pedestrian safety at crosswalks without leaving pedestrians stranded on one side of the street.

As the study authors noted, there is a "fundamental obligation to get pedestrians safely across the street."1 This obligation became the basis for the City of Seattle's crosswalk inventory and resulting crosswalk improvement work plan.

Zegeer, Stewart, Huang and Lagerwey studied 1,000 marked crosswalks and 1,000 unmarked crosswalks at uncontrolled locations in 30 cities throughout the United States. Multiple variables were examined, including pedestrian crash history, estimates of daily pedestrian volumes, average daily traffic (ADT) volume, number of lanes, speed limit, area type, median type, condition and type of crosswalk marking patterns and location type (midblock versus intersection).

Statistical analyses showed that higher pedestrian volumes, higher ADT and a greater number of lanes all were associated with an increased frequency of pedestrian crashes. Raised medians and raised crossing islands were associated with a lower pedestrian crash frequency. The study also found that on two-lane roads and low-volume multi-lane roads, the presence of a marked crosswalk alone at an uncontrolled location showed no difference in pedestrian crash rate compared to an unmarked crosswalk. On multi-lane roads with traffic volumes above about 12,000 per day, a marked crosswalk alone (without other substantial improvements) was associated with a higher pedestrian crash rate (after controlling for other site factors) compared to an unmarked crosswalk. Older pedestrians had a higher rate of crash experiences, based on crossing exposure.

Using these results, the study authors established a series of guidelines to determine where marked crosswalks alone do not increase the number of pedestrian crashes (see Figure 1). In summary, the study suggested that sites with two lanes are candidates for marked crosswalks alone ("C" crosswalks); sites with multiple lanes are candidates for marked crosswalks when ADT is low; and sites with high ADT are not candidates for marked crosswalks alone ("N" crosswalks). In between these two categories, "P" crosswalks are possible candidates for marked crosswalks alone.

There has been concern that some agencies may misuse the results of this study and do nothing more than remove marked crosswalks at certain locations, even though the study stated that, "The results of this study should not be misused as justification to do nothing to help pedestrians safely cross streets. Instead, pedestrian crossing problems and needs should be routinely identified, and appropriate solutions should be selected to improve pedestrian safety and access. Deciding where to mark or not mark crosswalks is only one consideration in meeting that objective."2

The study by Zegeer, Stewart, Huang and Lagerwey recommended a variety of improvements to help pedestrians cross at uncontrolled locations, including speed-reducing measures, traffic signals with pedestrian signals (where warranted), raised medians, curb extensions, improved roadway lighting, lane reduction and advance stop lines on multi-lane roads (to improve sight distance).