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Download report on Oakland's pedestrian scramble.

Evaluation of Pedestrian Scramble in Oakland, CA
TSC Website research summary.
 

Other Stories this Issue:

A Fifth Anniversary Message

Five Years of Traffic Safety Research

Youthquake to Jolt the Traffic Safety World

San Pablo SMART Corridor Designs for Multiple Mode Users

Toward "Healthier" (Safer) Urban Pedestrianism

A Step in the Right Direction: Oakland's Scramble

Latino Traffic Safety

Emeryville, CA: Walking with Cars

A Statistical Snapshot of the State

A Step in the Right Direction 

Experiences with a Scramble in Oakland's Chinatown

The large volume of pedestrians and cars converging on Oakland’s Chinatown district make it especially hazardous for people on foot, even compared to many other populated urban areas in California. That was underscored by a highly publicized death of a pedestrian in a crosswalk, which led community leaders and city officials to convene a pedestrian safety planning process which led to the installation of what is known as a scramble, a four-decade-old crossing system used widely overseas.

Scrambles are intersections where cars are stopped in all directions, and pedestrians are given an exclusive phase of the signal in all four directions, enabling them to cross diagonally as well as laterally and to do so without competition from turning cars. While they have been deployed on four continents—Asia, Australia, North America and Europe—conclusions about their usefulness have been mixed, partly because the unique effects from scrambles are difficult to isolate.

Researchers at the UC Berkeley Traffic Safety Center (TSC) provided technical assistance on the project to help answer questions such as:

• How does a scramble affect the rate of pedestrian-vehicle conflicts at an intersection?
• How does the four-way walk signal affect the number of pedestrians committing crossing violations?
• Are the results of the scramble system at this location (8th and Webster Sts.) consistent with what was found at other scramble sites?

To start with they performed a literature review on the topic of scrambles and followed that with "before" and "after" measurements of conflicts–e.g., pedestrians forced to speed up or change paths to avoid cars, or near-misses—with conflicts standing in as proxies for collisions, because they are so rare as to fail to show up in meaningful numbers during conventional observation periods.

In the literature review, researchers found that, generally, where vehicle volumes were high, scramble phasing reduced crashes and traffic accidents. Moreover, in sites with high pedestrian volumes that also experience high rates of conflicts between pedestrians and turning vehicles, scramble phasing has been especially effective.

One series of locations in Beverly Hills recorded a 66 percent drop in such conflicts after scrambles were installed. However, researchers at sites in Europe found that scrambles resulted in more pedestrians crossing against the red after they lost patience during the longer-than-usual waits associated with scramble phasing. Studies in Israel of low-volume sites with few crashes found that scrambles made little difference in conflicts and crashes.

TSC researchers took this information and applied it to the characteristics of the Oakland Chinatown intersection at 8th and Webster Sts. It is made up of two four-lane streets of one-way traffic. Vehicle volume is as much as 4,000 per hour, and pedestrian volumes are approximately 3,000 per hour at peak times, an especially high volume due to the presence nearby of BART stations, large office buildings, and other sources of pedestrian traffic.

There is significant potential for conflicts, because 30 percent of the vehicles entering the intersection execute a turn. At the same time, there is heavy congestion much of the time, and the intersection's signals are part of a coordinated series of traffic signals designed to minimize vehicular delay. This is a potential source of conflict between optimizing vehicle flow and maximizing safety because the scramble approach is a fundamental departure from most signal systems.

“The scramble does not minimize delay to users, nor does it maximize the vehicle capacity of the intersection, common objectives of signal timing,” TSC researchers noted. As a result, the scramble signals had to be adjusted to accommodate the larger network of signals while still giving ample time to pedestrians.

Researchers used historical data from the Statewide Integrated Traffic Records System to get a measure of the number, type, and severity of collisions in the intersection for the five-year period from 1996 through 2001. They found that there had been five collisions involving pedestrians, and all occurred within six feet of the intersection. Three involved injury, and one was a fatality. Researchers also observed pedestrians and found many instances when they left the curb against the signal. Drivers, too, displayed dangerous behavior like entering crosswalks while waiting to turn on red and turning after waiting for the light to go red because delays lasted entire cycles.

At the same time that the scramble was installed, TSC staff and members of the community conducted extensive public outreach, including handing out multilingual brochures, conducting workshops, and answering questions from pedestrians. Trained volunteers were stationed at the four corners of the intersection to act as guides. Police also increased patrols during peak times for the first six weeks.

To assess the pedestrians’ reactions, TSC researchers mounted a camera to record pedestrian-vehicle interactions. They then analyzed the recordings using a checklist of criteria. They found that scramble signalization increased the instances of pedestrian non-compliance with signals but also reduced the number of pedestrian-vehicle conflicts. These conflicts dropped 50 percent from 77 to 35 in a three-hour observation period, while pedestrian violations increased slightly from 12 to almost 15.

The TSC noted that increased non-compliance hasn’t resulted in subsequent conflicts with vehicles.

“Although these results indicate that the introduction of scramble phasing has improved pedestrian safety by reducing conflicts, it is important to note that it is difficult to pass judgment on the scramble’s overall value to society without a complete analysis of the effects of vehicular delay and route diversion,” the researchers concluded.

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This report (PDF) provides a detailed description of the intersection characteristics and research methodologies (including use of cameras) employed in the study of a downtown Oakland scramble intersection.

Evaluation of Pedestrian Scramble in Oakland, CA - TSC Website research summary.
 

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