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35 There have been a number of state-specific exemptions to Changes in truck size and weight regulations, in coordina- federal gross or axle weight limits authorized since 1982, in- tion with complementary changes in the management of cluding four states granted exemptions by the Transportation the highway system, offer the greatest potential to improve Equity Act for the 21st Century (TEA-21) in 1998. Increasing the functioning of the system. the semitrailer length in some states has resulted in increased The methods used in past studies have not produced satis- cubic capacity. Since 1981, the standard semitrailer length has factory estimates of the effect of changes in truck weights increased from 13.72 m (45 ft) to 14.65 m (48 ft) to 16.20 m on bridge costs. (53 ft). Some states allow semitrailers up to 18.29-m (60-ft) It is not possible to predict the outcomes of regulatory long. A decrease in cargo density has actually driven the aver- changes with a high degree of confidence. age operating weight of tractor-semitrailers downward It is important to examine the safety consequences of size slightly in recent years. The increase in semitrailer length to and weight regulation. Research is needed to understand 16.20 m (53 ft) has not had serious consequences, because the relationship of truck characteristics and truck regula- even in the absence of a state limit on wheelbase, or the equiv- tions to safety and other highway costs. alent kingpin-to-axle dimension, most of these semitrailers Violations of size and weight regulations are considered an operate with the bogie in a forward position to control off- expensive problem, but monitoring of compliance with the tracking. Overall, however, these changes have only increased regulations is too unsystematic to allow the costs involved the diversity in truck size and weight nationwide. Increasing to be estimated. trade with Canada and Mexico will exert pressure to increase limits in the United States. The Uniformity Scenario would The major recommendations of this study were as follows: virtually eliminate this lack of uniformity, but there is little Congress should create an independent public organi- sentiment to roll current limits back to these levels. zation charged with observing and evaluating commercial Cost recovery is another significant issue when consider- motor vehicle performance and the effects of size and weight ing an increase in truck size and weight limits, which will regulation, which the committee called the Commercial Traf- undoubtedly increase the cost to maintain the infrastruc- fic Effects Institute. The Institute could enter into agreements ture. Some states capture a large share of these costs through with private sector entities to conduct joint programs of data permit fees, but other states undercharge for increases and collection and research. The legislation creating the Institute barely cover their administrative costs. There is no means at should define the scope of its activities by specifying three the federal level to recover the cost of larger and heavier distinct functions: trucks. The conduct of pilot studies of proposed new vehicles and related operating principles; 3.3.4 Review of Truck Size Monitoring and ongoing program evaluation to measure and Weight Limits whether practices intended to control safety and operations The 1998 TEA-21 directed the Secretary of Transportation were functioning as intended; and to request TRB "conduct a study regarding the regulation of Support for state implementation of federal size and weight weights, lengths, and widths of commercial motor vehicles regulations. operating on Federal-aid highways to which Federal regula- tions apply . . . and develop recommendations regarding any Congress should authorize the Secretary of Transportation revisions to law and regulations that the Board determines to approve pilot studies of temporary exemptions from fed- appropriate" (71). TRB formed the Committee for the Study eral size and weight regulations. A pilot study is defined as a of the Regulation of Weights, Lengths, and Widths of Com- controlled experiment designed to measure the effects of mercial Motor Vehicles to conduct the work (69). changes in truck size, weights, or operating practices. The major conclusions of this study were as follows: Federal law should allow any state to participate in a feder- ally supervised permit program for the operation of vehicles Opportunities exist for improving the efficiency of the heavier than the present federal gross weight limit, provided highway system through reform of federal truck size and the state meets the requirements of the program. The Com- weight regulations, which reform may involve allowing mercial Traffic Effects Institute should monitor the conse- larger trucks to operate. quences of the federally supervised permit program, but the Federal truck size and weight regulations should facilitate overall federal role in defining numerical dimensional lim- safe and efficient freight transportation and interstate its would be diminished. Instead, the federal government commerce, establish highway design parameters, and help would have greater involvement in ensuring that state reg- manage consumption of public infrastructure assets. ulations pertaining to vehicles on federal-aid highways were