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Optimal Speed Limits for School Buses on Virginia Highways: A Report to Virginia's Superintendent of Public Instruction
Jernigan, Jack D.
Cheryl W. Lynn
Year: 1990
VTRC No.: 90-R9
Abstract: On Virginia's rural interstate highways there is a three-tiered speed limit: 45 mph for school buses, 55 mph for trucks, and 65 mph for other vehicles. On the urban interstate highways, school buses are restricted to 45 mph, but other traffic has a 55 mph speed limit. Speed theory suggests that (1) restricting school buses to slower speeds will not increase the potential severity of accidents that occur but that (2) slower speeds may function to increase the probability that a school bus will become involved in a crash with a faster-moving vehicle on the interstate highway system.The study found that 41 states allow school buses to travel at least 55 mph on the interstate highway system, and 22 states allow school buses to travel 65 mph on the rural interstate highways. Surveys of school administrators, school bus drivers, and policeagencies and other special interest groups indicated a majority opinion in favor of raising the speed limits for school buses from 45 mph to 55 mph on the rural interstate highway system but retaining the 45 mph maximum limit on the urban interstate highways and on other systems. A major reason cited for wanting an increase on the rural interstate highways was a fear that school buses are in danger of being struck from behind by faster-moving vehicles, especially heavy trucks. A detailed analysis of four years of Virginia accident data (including the one year of exposure to the 65 mph rural interstate speed limit for most traffic) indicated that only 17 crashes occurred during those years, resulting in only six injuries and no fatalities. These crashes were not attributable to the difference in speed limits or to collisions between heavy trucks and school buses. The accident data, therefore, did not support the reasons given by those surveyed for why a higher speed limit would be preferred. Further, because Virginia's school buses are equipped with a speed governor that limits the maximum speed of the bus, a higher speed limit would require raising the speed allowed by the governor. Therefore, this action might function to increase travel speeds not only on interstate highways but on other roads as well, which could have a deleterious effect on school bus safety on the primary and secondary systems. Thus, the study concluded that there are no compelling reasons for Virginia to raise the maximum speed limits for school buses from 45 mph and that there are reasons that caution against raising the speed limit.