Differences in regulations and design philosophies have brought about the development of significantly different hardware in the braking systems of U.S. and European heavy vehicles. In the service braking system, for example, European heavy vehicles generally have larger front brakes than their U.S. counterparts,a nd they are usually equipped with load-sensing brake proportioning valves (not used on U.S. vehicles). Emergency brake systems and parking brake systems are also different. This paper discusses those differences that have a significant impact on safety-relatedp erformance and present the results of recent tests that were run to compare the braking performance of a U.S. five-axle tractor semitrailer combination to a European vehicle of the same basic size, weight and axle configuration in various simulated accident avoidance maneuvers.