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Citation |
Willey WE. Highw. Res. Board bull. 1955; 104: 21-33. |
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Copyright |
(Copyright © 1955, National Research Council (U.S.A.), Highway Research Board) |
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DOI |
unavailable |
PMID |
unavailable |
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Abstract |
Research was conducted by the arizona highway department on the uphill and downhill speed characteristics of heavy trucks on long, steep mountain grades, and the congestion caused by slow-moving vehicles on uphill grades. It was concluded that the only way to speed up the travel of passenger cars through the hills was to provide a means of removing the slow vehicles from the normal path of travel negotiated by the faster automobiles. The matter of economics and general lack of overall highway revenue prompted further investigation into evaluating the congestion caused by these slow-moving vehicles. The downhill study showed that trucks generally assume speed characteristics commonly associated with passenger vehicles. Uphill speeds are determined by the hill-climbing ability of the truck. From the survey, a delay chart was constructed showing the maximum and minimum days of traffic congestion related to number of cars being delayed, as well as the total hours of delay during the day. The delay to each vehicle caused by slower-moving traffic in the same lane was computed. The money value of the delays was evaluated with other economic factors. A cost analysis for construction and maintenance was made and related to savings to the motorist in a benefit ratio comparison. Capital costs far exceeded the benefits that could be expected. Three passing bays were constructed and were located at the bottom, middle, and near the top of the hill. Because of the bad alignment and sight distance, these locations represented the areas of greatest congestion. A before-and-after study was made of the passing bays. |