Vehicle hoods are now four inches taller and 22 percent more deadly for pedestrians

By Megan Link 

Vehicles keep getting larger and heavier. Increasing a vehicle’s size not only increases emissions, it also has important implications for pedestrian safety, increasing the risk of injury and death on the road. Many studies have looked at the predominant factors that heighten risk for pedestrians. A new study from the University of Hawaii analyzes both crash data and physical vehicle measurements, rather than focusing on vehicle types, to determine a leading factor in pedestrian death rates: the front-end height of a vehicle.  

Understanding the main risk factors for pedestrians can lead to important policy and design changes. The increased height of vehicle front-ends can be more dangerous for a person because the higher area of impactoften the chest and head—is more likely to result in fatalities. A previous study by IIHS looked at data from 18,000 pedestrian crashes and determined that hood heights over 40 inches increase fatality risk by 45% compared to smaller vehicles with hood heights under 30 inches.   

The University of Hawaii study used U.S. crash data with public data on vehicle dimensions to analyze over 3,400 crashes where pedestrians were hit to identify the key factors leading to increased pedestrian risk. The study finds that a 4 inch-increase in vehicle front-end leads to a 22% increase in fatality risk for a pedestrian. 

A higher front-end increases the fatality risk in women, children, and the elderly more than in men. “A 4 in. increase raises the death probability of 18- to 65-year-old pedestrians by 21%,” according to the authors, “while it raises the probability a child pedestrian will die by 81%, roughly four times the effect among adults.” 

Several other factors change the probability of pedestrian survival, including: 

  1. Slope of the front-end: The blunter, or more vertical a front end is, the more dangerous it is for a pedestrian, increasing fatality risk by 26% compared to vehicles with sloped fronts. The authors of the study conclude, “Manufacturers can make vehicles less dangerous to pedestrians by lowering the front end of the hood and angling the grille and hood to create a sloped profile…There’s no functional benefit to these massive, blocky fronts.”  
  2. Speed: “Increasing a vehicle’s speed from 30 mph to 40 mph raises the probability of pedestrian death by 111%. Increasing speed from 30 to 50 mph raises the probability of death by 312%. Vehicle speed dramatically increases the probability the pedestrian dies.” 
  3. Time of day: Pedestrian death rates are three times higher at night compared to daylight hours. 

The study includes important policy implications. The author suggests a vehicle front-end cap of 1.25 meters (around four feet). He estimates that a design cap will help to save over 500 pedestrians each year if vehicle front-end design would decrease in size. 

Photo Credit: Nasr Al via Pexels, unmodified. License