This study deals with two-lane rural highways and the effect of their geometry on flow characteristics. Several design measures representing road geometrics and traffic were developed. The layout measures that were adopted as independent variables for the suggested models represented the horizontal and vertical alignments, and were the average curvature, average hilliness, and net gradient. The traffic parameters considered were the volume, density, percentage of trucks and directional distribution of traffic. Based on tests of several alternative functional forms, it is shown that one and two-regime multiple linear regression models may be used for prediction of the average running speed on two-lane rural highways. It is also shown that either volume or density can serve as independent traffic parameters along with the percentage of trucks and directional distribution of traffic. The calibration results of the models are presented and evaluated. Calculations of two-way rural highway capacities for level, hilly, and mountainous terrains show that the values obtained are less sensitive to percentage of trucks than are currently recognised capacity values. The suggested capacities are also higher than the current values, particularly for the upper percentage range of trucks.(a) for the covering abstract of the proceedings see IRRD 274491.
Samenvatting