The purpose of this study was to evaluate economic utility or cost of resources consumed by the highway transportation industry for various speeds of travel in rural and urban areas for passenger cars and commercial vehicles on 2- and 4- lane streets and highways during daytime and nighttime travel. Graphical relationships of economics of vehicle operation, values of time, safety of travel, and their sum, which is defined as the total cost of traffic movement, were drawn for the various conditions. The minimum point on each total cost curve represents that speed at which the cost of traffic movement is minimized. Results indicated that there was a speed which minimized the cost of traffic movement for each of the various conditions considered. This speed was defined as the optimal speed. In rural areas the optimal speed was 50 mph for passenger cars and 41 mph for commercial vehicles. Optimal speeds in urban areas decreased with an increase in number of stops per mile from 41 to 29 mph for passenger cars and from 36 to 25 mph for commercial vehicles with 1 and 8 stops per mile, respectively. The most direct application of the results is likely to be in the establishment of statewide or areawide speed limits where the limit is established so that the mean speed of the vehicles coincides with the optimal speed. /author/.
Abstract