One potential barrier to trade is the differing safety standards testing and requirements for vehicles sold in the EU and the US. Testing the same make/model under both regimens is an expensive process, and negotiation of common standards may be difficult and time-consuming. However, if vehicles are shown to provide similar real-world safety protection to the occupants, then vehicles that meet EU regulations could potentially be recognized for sale in the US, and vehicles that meet US regulations could potentially be recognized for sale in the EU.

Therefore, a study investigating the question of essentially equivalent safety performance was sponsored by the Auto Alliance in the US. Independent experts from UMTRI and Safer carried out the study. To compare risks, the researchers analysed a number of US and EU crash data sources using three statistical approaches to “triangulate” evidence regarding differences in crash and injury risk. Separate analyses assessed crash avoidance technologies, including headlamps and mirrors.

This report describes Phase II (implementation of analysis) of a project to develop and implement a statistical methodology to investigate the hypothesis that passenger vehicles meeting EU safety standards would perform equivalently to US-regulated passenger vehicles in the US driving environment, and that vehicles meeting US safety standards would perform equivalently to EU- regulated vehicles in the EU driving environment. To answer this question, it was necessary to separate risk from exposure because EU and US drivers drive in different environments. Risk is the probability of injury given a particular set of circumstances; exposure is the particular collection of those circumstances. In addition, regulation affects both risk of a crash (crash avoidance) and risk of injury given a crash (crashworthiness). These analyses were carried out separately because the relevant datasets and outcomes are different.

For the crashworthiness analysis, we represented risk (of injury in a particular crash) using a statistical model that could be applied to different environments. For crash avoidance, we selected a crash subpopulation and control crashes to adjust for any exposure differences between the EU and US. For both crashworthiness and crash avoidance, the comparison of injury risk given a particular set of crash characteristics, respectively the comparison of crash involvement, was then argued to be driven by differences between the vehicles themselves.

—Flannagan et al.

The results suggest that when controlling for differences in environment and exposure, vehicles meeting EU standards offer reduced risk of serious injury in frontal/side crashes and have driver-side mirrors that reduce risk in lane-change crashes better, while vehicles meeting US standards provide a lower risk of injury in rollovers and have headlamps that make pedestrians more conspicuous. More precisely, the project results support the following conclusions:

• The EU and US injury risk models are different for both front/side crashes and rollovers.

• Though the range of estimates is wide, overall risk across both the US and the EU front-side crash population (given the selection criteria for this study,) is likely lower for EU vehicles. Risk differences in front/side crashes are largest for near-side crashes, middle occupant ages (31-70), unbelted occupants, and higher crash severities (measured in terms of the change of velocity in the crash).

• Overall risk across both EU and US rollover crash populations is lower for US vehicles. In rollovers, risk differences were highest for unbelted occupants and ejected occupants.

• US ratio of pedestrian fatalities in dark vs. light is estimated to be lower than in the EU. One possible explanation for this is that headlamps in US vehicles may illuminate pedestrians better than those in EU vehicles.

• EU ratio of driver-side lane changes compared to passenger-side lane changes, based on data from only two EU countries, is lower than in the US. One possible explanation for this is that driver-side mirrors in EU vehicles reduce risk in lane-change crashes better than those in US vehicles.

Further work should be done to replicate the results, identify artifacts that may have influenced the patterns seen, and/or find evidence for mechanisms linking the results to vehicle design differences that result from regulatory differences, the researchers said.

Both unexpected and expected results should be looked at closely to identify those that

can be replicated and those that may be influenced by unforeseen data or population factors rather than regulatory differences.

Future reproductions and extensions of this study would greatly benefit from the availability of harmonized accident data. Hence, further data collection and data harmonization efforts are encouraged.

Resources

• Flannagan, Carol A.C.; Balint, Andras; Klinich, Kathleen D.; Sander, Ulrich; Manary, Miriam A.; Cuny, Sophie; McCarthy, Michael; Phan, Vuthy; Wallbank, Caroline; Green, Paul E.; Sui, Bo; Forsman, Asa; Fagerlind, Helen (2015) “Comparing motor-vehicle crash risk of EU and US vehicles”