The operational effectiveness of restricting trucks from designated lanes on multilane roadways is addressed. Three locations with no truck restrictions were treated with signing restricting trucks to certain lanes. The applied field study was of a before-and-after design (with matched control sites). Truck lane restrictions were implemented at two three-lane sites and one two-lane location. Favourable truck compliance effects were evident at all three locations. Before-and-after comparisons indicated significant truck lane use shifts;however, violation rates were higher (i.e., 10.2%) At the two-lane site in comparison with the three-lane sites (i.E., 0.9% And 5.7%). Higher violation rates at the two-lane site resulted from increased truck densities caused by restricting trucks to a single lane. An emphasis was placed on determining traffic flow effects to nontrucks in the traffic stream. Beneficial effects on three-lane roadways were realised in terms of reduced congestion and fewer trucks impending vehicles (at both sites) and shorter following queue lengths (at one site). This finding supports the conclusion that traffic congestion at three-lane sites was reduced as the result of the restriction. An adverse effect, observed at the two-lane restriction, was reduced speeds of impeded vehicles following trucks. However, a slight benefit was found in that fewer trucks impeded following vehicles. All-vehicle speed comparisons were examined to determine whether increased differential speeds were likely to occur between the restricted and adjacent lanes. No speed changes were observed to indicate an adverse effect of the truck lane restriction. This paper appears in Transportation Research Record No. 1281, Human Factors and Safety Research Related to Highway Design and Operation 1990.
Samenvatting