The highway investment analysis package (hiap) released by the federal highway administration in 1976 was revised so that the methodology for estimating operating speeds and costs would be consistent with the results of recent research. the hiap procedure for accounting for fluctuations in the daily distribution of traffic was first modified to more accurately reflect flow conditions during the busiest hours of the year. the procedure for estimating average travel time under a given congestion level was then revised to be compatible with the 1985 highway capacity manual methodology. finally, vehicle operating cost data were updated, and the cost estimating procedures were modified to be more sensitive to changes in highway alignment. the new fortran code was then validated and tested. this paper appears in transportation research record no. 1156, transportation systems planning and management.
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