CHANGES IN LEGAL VEHICLE WEIGHTS AND DIMENSIONS: SOME ECONOMIC EFFECTS ON HIGHWAYS

This report which was prepared from a review of literature, contains information on the principal factors involved in the construction, operation and maintenance of the highway system that are related to vehicle weights and dimensions, as well as presentes an analysis of these factors for their impacts on benefits and disbenefits to highway users and non-users. Methods have been assembled from the state of the art that permit projection of estimated use of highway facilities by various classes of commercial vehicles, the division of motor freight among vehicle classes on principal types of highways, and estimated payloads these vehicles will transport. Details are given of two separate estimates that are proposed. One estimate projects the foregoing factors on the assumption that no change is made in present legal limits the second estimate repeats the process, with the assumption that the proposed limits are put into use. Pavement structural weakening is estimated by using equivalent 19-kip simple-axle equivalence factors developed in the AASHO Road Test and modified to conform to local conditions where such correlations have been established. Two methods for estimating cost impacts on existing and planned pavement structures, varying in scope and detail, are recommended. A numerical example is presented of the application of each method. A method is also presented for estimating the accident incidence rate for vehicles whose speed distribution is different from average highway speed, originially applied as warrants for truck climbing lanes. Highway classification and needs studies and methods of highway costs allocation are reviewed, as well as, oversize and overweight permit operations. The benefits resulting from changes in legal limits are identified and disbenefits, penalties that may be imposed on other users of the highways as a result of the increases in legal limits, are dicussed. Based on this study, the observation is made that a cost/benefit analysis method can be applied as a limited decision factor within the present state of the art. The method for this application would scale the costs required to construct one mile of new highway, including a pro rate share of bridge structures to the benefits of the track operator in reducing the operating costs of moving motor freight over the hypothetical mile.

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 184 p.
  • Serial:
    • NCHRP Report
    • Issue Number: 141
    • Publisher: Transportation Research Board
    • ISSN: 0077-5614

Subject/Index Terms

Filing Info

  • Accession Number: 00272102
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: Sep 30 1974 12:00AM