Vehicles have gotten a lot bigger over the last few decades, particularly when it comes to trucks and SUVs. In particular, hood heights have gotten much taller as trends have shifted towards taller, more aggressive designs. The trend has raised safety concerns around visibility and pedestrian impacts, particularly when it comes to small children. A new research paper has found significant correlations between larger vehicles and pedestrian fatalities.
The study is the work of Justin Tyndall, an Assistant Professor of Economics at the University of Hawaii. Tyndall’s research focuses on cities, transport, and housing. His latest paper, The effect of front-end vehicle height on pedestrian death risk, is published in the upcoming March 2024 edition of Economics of Transportation, and also available on his personal website.
Tyndall’s hypothesis was that vehicles with taller front-end designs could be more dangerous for pedestrians in a crash. In these incidents, the higher front-end is more likely to make contact with a person’s head or torso, inflicting greater injuries. In contrast, a vehicle with a lower hoodline might instead hit a pedestrian’s legs, where injuries are less likely to be fatal. Motivating this research are the sobering statistics on pedestrian deaths from traffic collisions, which hit approximately 7,400 fatalities in 2021, up 77% compared to 2010.
Earlier studies have been done in this area, but many haven’t been able to drill down into specifics like hood height due to the limitations of available data. Tyndall’s point of difference was to source vehicle measurements using the VINs of vehicles that show up in U.S. & Canadian crash data. The paper features a basic analysis of pedestrian deaths per vehicle category, which shows that pickups and SUVs are most likely to cause a pedestrian fatality in the event of a collision. But it’s the statistics on front-end height that prove the most telling.
Armed with this data, Tyndall was able to more precisely analyze the relationship between vehicle size and pedestrian deaths. His analysis determined that front-end height is the best predictor of pedestrian fatalities versus any other vehicle dimension, like weight or wheelbase. For a 3.93-inch (10 cm) increase in front-end height, Tyndall found there was a 22% increase in the probability of a pedestrian death. This analysis controlled for other factors like crash characteristics, to ensure a fair comparison.
The study also determined that women, children, and the elderly were more strongly affected in this regard. Tyndall suspects that this could be in part related to the lower average body height for women, similarly for children and older people.
Split across these categories, the data gets interesting. A 3.93-inch (10 cm) increase in hood height raises the risk of fatality by 19% for male pedestrians. For female pedestrians, it goes up by 31%.
Taking the same 3.93-inch increase in height, for those aged 18-65, the risk increases by 21%. For those over 65, the increase is a higher 31%. The results are the most sobering when it comes to children, however. For those under 18, the probability of death goes up by a whopping 81%. That’s four times higher than in adults, and suggests that shorter individuals may be at much greater risk from vehicles with super-tall bonnet lines.
Tyndall suggests there is scope to improve pedestrian safety by limiting hood heights. If front-end heights were limited to 49.2 inches (125 cm), he estimates there would be 500 fewer pedestrian fatalities every year. He bases this number off the approximate hood height of a Honda CR-V. The SUV is taller than most traditional car body styles, but measurably lower than larger SUVs and trucks on the market.
Of course, Tyndall isn’t the only one looking at this problem. The Insurance Institute of Highway Safety published similar conclusions last year. The agency determined that vehicles with tall front ends were more dangerous to pedestrians. Furthermore, it found that medium-height vehicles with blunter, more vertical front-end designs were also more dangerous. Ultimately, it found that pickups, SUVs and vans with hoods over 40 inches were far more dangerous for pedestrians in the event of a collision. They were 45% more likely to cause a fatality compared to other vehicles with more sloping designs and hood heights of 30 inches and below.
Similarly, a study from the European Transport Safety Council concluded that SUVs and pickups made roads more dangerous for pedestrians, cyclists and car occupants alike. It similarly found hood height to be predictive of greater harm. “A pedestrian or cyclist hit by a car with a bonnet 90 cm [35.4 inches] high runs a 30% greater risk of fatal injury than if hit by a vehicle with a bonnet 10 cm [3.93 inches] lower,” read the study release, a notably similar figure to Tyndall’s own findings.
Anyone can look at a big SUV or pickup truck and guess that it might be more of a threat in the event of a collision with pedestrians. Beyond that, it’s clear that multiple studies have found numbers to back that up. Whether it leads to any change in vehicle design standards remains to be seen, but regulators would certainly have plenty of data on their side if they were to move in that direction.
Image credits: Title – Sven D via Unsplash License, Figures – Justin Tyndall via research paper, Chevy, IIHS