Trucks and buses are larger, heavier, and less maneuverable than passenger cars and make up an increasingly larger proportion of the traffic on U.S. highways. This synthesis addresses the safety interactions of commercial trucks and buses with highway features and the highway improvements that can be made to improve the safety of heavy vehicle operations. This synthesis presents the state of knowledge and the state of practice concerning the accommodation of heavy vehicles on the highway. The synthesis is based on a comprehensive literature review and a survey of highway agencies and the trucking industry. A wide variety of heavy vehicle types-including single-unit trucks, combination trucks with one, two, or three trailers, and buses-operate on U.S. highways. The physical and performance characteristics of heavy vehicles that interact with highways include vehicle types and configurations, weights and dimensions, turning radius, offtracking and swept path width, trailer swingout, braking distance, driver eye height, truck acceleration characteristics, rearward amplification, suspension characteristics, load transfer ratio, and rollover threshold. Many highway geometric design criteria are based on vehicle characteristics. In many cases, truck and buses are the most critical characteristics used in defining these design criteria or assessing their appropriateness. Highway geometric design features whose design is based on consideration of vehicle characteristics include sight distance, upgrades, downgrades, acceleration lanes, horizontal curves, intersection design, interchange ramps, and roadside features. Traffic control devices and traffic regulations have an important role in safely accommodating heavy vehicles on the highway and can be used by highway agencies to better accommodate trucks at locations where safety problems have occurred or are anticipated. The traffic control device strategies that have been used, or are being considered, to better accommodate heavy vehicles on the highway include differential speed limits for passenger cars and heavy vehicles, heavy vehicle prohibitions on particular roads, lane use restrictions for heavy vehicles, exclusive lanes and exclusive roadways for heavy vehicles, signing for long downgrades, signing and marking of interchange ramps, mitigating the restriction of sign visibility by heavy vehicles, and modifying signal timing to better accommodate heavy vehicles. Highway agencies are increasingly using intelligent transportation system (ITS) initiatives to more effectively communicate with heavy vehicle drivers and provide realtime information concerning safe vehicle operation. The types of ITS systems in current use by highway agencies include warning systems for long downgrades, dynamic curve warning systems, and improved weigh station operations. ITS initiatives related to heavy vehicle safety also include on-board vehicle technology such as collision avoidance systems for buses.