
A recent study by the Insurance Institute for Highway Safety (IIHS) reveals that the height of a vehicle significantly impacts the severity of injuries sustained by pedestrians in crashes. The research shows that taller vehicles, such as SUVs and pickups, compound the risk of serious injuries at higher speeds.
IIHS researchers analyzed pedestrian crashes to develop injury risk curves, demonstrating how speed affects crash outcomes. They found that the effect of crash speed on injury risk is magnified for vehicles with taller front ends. Compared to European data, where tall passenger vehicles are less common, U.S. risk curves indicate that pedestrians begin to suffer more serious injuries at lower speeds.
“A small increase in crash speed can really ramp up the danger to a pedestrian,” said IIHS president David Harkey. “Our fondness for tall SUVs and pickups in the U.S. has intensified that effect.”
The study suggests that the 25 mph (40 km/h) speed limit commonly used in North American residential neighbourhoods may be too high for areas with heavy pedestrian traffic. To estimate injury risk at different speeds, IIHS researchers examined 202 crashes involving pedestrians aged 16 or older, using data from Michigan, California, New Jersey, and Texas.
Researchers determined the height of the vehicle models’ front hoods and analyzed the impact of vehicle speed and height on injury severity. They focused on front-end height, as it determines the point of impact on a pedestrian’s body, a key factor in injury severity.
Higher speeds were associated with increased injury risk regardless of vehicle height. Pedestrians struck at 20 mph (32 km/h) had a 46% chance of sustaining moderate injuries and an 18% chance of serious injuries. At 35 mph (56 km/h), the risk of moderate injury rose to 86%, and serious injury risk climbed to 67%. Fatalities also increased with speed, with a 1% chance of death at 20 mph, 19% at 35 mph, and over 80% at 50 mph (80 km/h).
Taller vehicles increased the likelihood of both moderate and serious injuries. At 27 mph (43.5 km/h), the average speed of the crashes studied, a median-height car had a 60% chance of causing moderate injuries and a 30% chance of causing serious injuries. In contrast, a median-height pickup had an 83% chance of causing moderate injuries and a 62% chance of causing serious injuries.
The study’s authors compared risk curves here with those from Germany and found that pedestrians here are more likely to be injured at all speeds, likely due to the prevalence of taller vehicles.
“Although SUVs are a growing share of the market in Europe, the passenger vehicle fleet there has long been dominated by cars. In contrast, the majority of passenger vehicles on U.S. roads today are SUVs or pickups,” said IIHS Senior Statistician Sam Monfort.
The findings highlight the need for policymakers and traffic engineers to consider the makeup of the vehicle fleet when setting speed limits and implementing traffic calming measures. A commonly used benchmark for a “safe” crash speed is one at which the risk of serious injury is 10% or less, which this study found to be around 15 mph (24 km/h).
Vehicle manufacturers also play a role in improving pedestrian safety by modifying front-end designs and equipping vehicles with robust automatic emergency braking systems IIHS’s report noted.
“This study is a vivid illustration of how multiple factors — in this case, speed and vehicle height — converge to create negative outcomes on the road,” Harkey said. “Similarly, it will take a combination of actions from different corners of the transportation world to improve pedestrian safety.”
Image credit: Depositphotos.com
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