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April 03, 2013  |   Comments (0)   |   Post a comment

Study points to risks of 'permitted' left turns

By Thomas McMahon


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Researchers say that this driving simulator illustrates the complexity of the permitted left turn: watching the signal, watching the traffic and watching for pedestrians at the same time. Image courtesy of Oregon State University.
<p>Researchers say that this driving simulator illustrates the complexity of the permitted left turn: watching the signal, watching the traffic and watching for pedestrians at the same time. Image courtesy of Oregon State University.</p>
CORVALLIS, Ore. — A study on "permitted" left turns found that about 4% to 9% of the time, drivers don't look to see if there are pedestrians in their way.

Researchers at the Oregon State and Portland State universities said that permitted left turns are often allowed by a "confusing hodgepodge" of signals, and drivers may have to pick their way through narrow windows of oncoming traffic.

Permitted left turns are distinguished from protected left turns, in which a solid green arrow gives drivers the complete right of way.

The researchers said their study found that permitted left turns present an “alarming” level of risk to unwary pedestrians crossing the street.

“There are far more pedestrian crashes in marked crosswalks than anywhere else on roads, and pedestrians already have a false sense of security,” said David Hurwitz, an assistant professor of transportation engineering at Oregon State University and the study's principal investigator. “This study found that one key concern is permitted left turns.”

The research showed that as drivers wait to make a permitted left turn, they focus mainly on the traffic and the signal, rather than pedestrians, and often lunge into narrow openings in oncoming traffic. The heavier the traffic, the less attention paid to pedestrians, according to the study.

For the study, a controlled analysis was conducted in a full-scale driving simulator that monitored specific eye movements. Twenty-seven subjects experienced 620 permitted left turn maneuvers.

The analysis found that about one time in 10 or 20, the driver didn’t look to see whether a pedestrian was present before moving into the intersection. According to the researchers, this suggests a major level of risk to pedestrians if they assume that drivers will look for them and allow them to cross the street.

The researchers concluded that the danger is high enough that more states and cities should consider prohibiting permitted left turns while pedestrians are allowed to be in the crosswalk. In Washington County, Ore., traffic managers recently did that after getting a high number of complaints about pedestrian-vehicle conflicts.

“In traffic management, you always have multiple goals, which sometimes conflict,” Hurwitz said. “You want to move traffic as efficiently as possible, because there’s a cost to making vehicles wait. You use more fuel, increase emissions and waste people’s time. The permitted left turn can help with efficiency.

“But the safety of the traveling public is also critical,” he said. “Sometimes the goal of safety has to override the goal of efficiency, and we think this is one of those times.”

To read the study, go here.


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