Citation

Islam MN, Seneviratne PN. Transp. Res. Rec. 1995; 1497: 1-9.

Copyright

(Copyright © 1995, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

AASHTO guidelines on highway design have drawn criticism for their inability to deal with the uncertainty of traffic operations, costs, and physical constraints. Some analysts believe that in light of changing economic and socio-environmental values, new procedures are needed to better address uncertainties and to justify engineering decisions. An analytical model that could be used to determine the optimal design curvature for horizontal curves on two-lane highways is presented. The optimal curvature results in the minimum total cost, defined as the sum of construction, maintenance, and expected user costs. The expected user cost is the sum of expected accident, travel time, and vehicle operating costs. It is shown that: (a) optimal design curvature is highly sensitive to the skewness of the probability distribution of the required curvature; (b) when the mean operating speed is high, optimal design curvature does not change significantly with the changes of standard deviation of speeds compared with the low mean operating speed; and (c) when the mean operating speed is low, the polynomial model best represents the relationship between optimal design curvature and the standard deviation of the operating speeds. When the mean operating speed is high, the linear model best represents the relationship between optimal design curvature and the standard deviation of the operating speeds. The application of the model and sensitivity of the optimum to model parameters are illustrated using numerical examples.

Language: en

Keywords

Costs; Highway accidents; Mathematical models; Speed; Optimization; Highway engineering; Ground vehicles; Curves (road); Highway systems; Probability; Transportation personnel