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Copyright
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(Copyright © 1981, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing) |
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Abstract
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Vehicle-weight-shifting methodology is an important element in the economic analysis model for changes in vehicle size and weight limits. The existing models were analyzed based on data for truck weights gathered in Texas since 1954.
RESULTS of the analysis show that the pattern of vehicle weight redistribution varies with vehicle class, which suggests that each vehicle class be considered separately. The historical and current use patterns of each vehicle type, practical maximum gross vehicle weight, and equipment-replacement policies should all be considered in a forecast. The phenomena described by the demand and volume-constraint concepts were observed in three vehicle types. Steering-axle weight distribution was not affected by the 1975 change in the Texas weight law, which allowed gross vehicle weight to increase from 72,000 to 80,000 lb. tandem-axle weight from 32,000 to 34,000 lb, and single-axle weight from 18,000 to 20,000 lb. The assumption that the distribution in axle weights for each type of axle has the same ratio to gross weight was found to be basically sound. The analyses of distribution of multiplying factors reveal large discrepancies and the need for further investigation. The findings suggest that further study's warranted to produce a more-accurate methodology for forecasting vehicle weight distribution under any proposed size and weight limits. |