Covid-19: Crashes more likely to be fatal when roads are clearer, finds new study

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The Covid-19 lockdowns, which were in full effect across many jurisdictions worldwide in April 2020, led to dramatic decreases in traffic levels. However, contrary to what might be expected, clearer roads weren’t found to be safer, according to a new study by Texas A&M Transportation Institute (TTI).

The study found that, while there was a drop in the number of crashes in Texas of almost 50% during April, compared to previous years, the proportion of those crashes that were fatal rose by 50%. This meant that overall there was only a 20% drop in fatalities, meaning that any one accident was more likely to be fatal than it would have been when traffic levels were normal.

Researchers studied traffic in urban and rural settings in Texas, as well as crashes involving just one vehicle and those with more than one. They then grouped crashes into several categories: all single-vehicle, all multi-vehicle and urban multi-vehicle, urban single-vehicle, and rural single-vehicle and rural multi-vehicle.

While the numbers for both multi- and single-vehicle crashes were down by 55% and 23%, respectively, the proportion of crashes with at least one fatality rose by 14% for single-vehicle crashes and 59% for multi-vehicle crashes.

“With fewer vehicles on the road in April, it makes sense that we had fewer multi-vehicle crashes,” says TTI senior research engineer and CTS director Robert Wunderlich. “And there is evidence that the relationship is exponential, meaning that decreases in volume can have a greater than proportional effect on crashes. The reduction in single-vehicle crashes is more likely to be proportional to the decrease in traffic.”

Wunderlich’s team found that the proportion of urban multi-vehicle crashes that resulted in a fatality almost doubled.

Wunderlich says two factors affect traffic crashes: exposure and risk. Exposure is the amount of travel, and risk is the chance that travel will result in a crash, injury or death. Because there was less exposure to risk in April with fewer drivers on the road, the number of crashes went down. But fatal crashes only dropped by 20 percent during that period, so the risk of a fatal crash was greater than normal.

Speed is a primary determinant of crash severity, Wunderlich says, with a 10% decrease in speed producing 38% fewer fatalities and 27% fewer serious injuries. But excessive speed wasn’t the only culprit for the increase in fatality risk in April, he notes.

“For example, we found that peak-period average speeds on Houston freeways increased from less than 45 miles per hour to 65 miles per hour,” he says. “So all crashes occurred at higher, yet legal, speeds. We also found that the fatality risk in single-vehicle crashes rose only 10% in Texas urban areas and 18% on rural roads. This may indicate that excessive speeds are not as big an issue as the increase in average speed.”

Other risk factors for increased fatalities identified in the Texas Strategic Highway Safety Plan are impaired driving and distracted driving. Pedestrian safety is also one of the areas of growing concern in the plan. An examination of fatal pedestrian crashes indicated that the levels of prior years were matched in 2020.

“It’s an issue of how we behave when we’re behind the wheel,” Wunderlich says. “Basically, we reduce our risk when we slow down, pay attention and stay sober. Until we get self-driving cars, the best way to reduce risk is the old-fashioned way: by making safer choices.”

For more of the latest insight from Texas A&M Transportation Institute, don’t miss the latest edition of the TTI Podcast featuring an interview with its director Greg Winfree.

 

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Tom has edited Traffic Technology International magazine and the Traffic Technology Today website since May 2014. During his time at the title he has interviewed some of the top transportation chiefs in charge of public agencies around the world as well as chairmen and CEOs of multinational transportation technology corporations. Tom's early career saw him working on some the UK's leading consumer magazine titles. He has a law degree from the London School of Economics (LSE).