University of Texas study pinpoints dangerous intersections

Kristin McGrath
Red-light runners, left turns and crosswalks all make intersections a dangerous place to be. In fact, nearly half of all urban crashes occur at intersections, according to the Insurance Institute for Highway Safety. A recent study from researchers at the University of Texas at Austin's Cockrell School of Engineering has found that some intersections are more dangerous than others.
Frontage roads most risky
The most accident-prone intersections, according to UT researchers, are those along frontage roads, which run parallel to interstates highways and expressways. The reason? Drivers accustomed to the higher speed limits on an interstate may not slow down enough when they exit onto a frontage road. Moreover, they might not have sufficient time between exiting the interstate and making a turn onto a side road. That leaves drivers making rapid, and possibly unsafe, lane changes on the frontage road.
Flashing lights cause confusion
Some intersections are controlled by flashing lights. In some cases, traditional red, yellow and green traffic lights are adjusted to red or yellow flashing lights during periods of lower traffic. In other cases, flashing lights replace stop sights at intersections with poor visibility. Whatever the reason, these lights may be dangerous for drivers, according to the study. The researchers found that the accident risk at intersections controlled by flashing lights is three times that of other intersections.
The researchers surmised that drivers might be confused about how to respond to the flashing lights. Should they stop? Yield? Simply drive through? However, they also acknowledged that flashing lights are often placed at intersections that are more dangerous in the first place. So the increased number of accidents might stem from the intersection itself, rather than the lights.
Traffic signals mean safety -- sometimes
The accident risk is lowest at intersections with traditional traffic signals, the researchers found. However, when an accident is imminent, these intersections become more dangerous than those that are less controlled. Intersections controlled by traffic lights generally have several lanes of traffic -- and, oftentimes, several turn lanes. If a driver sees someone about to run a red light, he has nowhere to go that wouldn't involve hitting another car.
Cause and effect
The study also found a silver lining when it comes to intersection crashes. Intersections are not isolated -- they're part of interconnected road systems. The researchers took a closer look at how intersections affect accidents on other parts of the road and found that improving just one intersection can have a positive ripple effect, reducing accidents at nearby intersections.
“Improving just one intersection could have broader regionwide benefits,” the study's leader, Professor Chandra Bhat, said in a news release. “If you don’t account for this dependence, which is what almost all earlier studies have done, you underestimate the value of roadway and traffic control improvements.”

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