OPERATIONAL EVALUATION OF PASSING LANES IN LEVEL TERRAIN: FINAL REPORT

As traffic flow intensity increases on rural highway systems, the governmental agencies responsible for these systems face a growing problem. Namely, conversion to multi-lane highway facilities may not be possible because of a lack of funding, project improvement stipulations requiring the incorporation of less expensive design modifications, a combination of these two reasons, or a number of other funding related reasons. In the absence of severe funding restrictions, conversion of two-lane rural highways experiencing undesirable levels of service to multi-lane highways would in most cases be the best solution. However, in the case of limited funding other cost-effective solutions which are within the constraints of the given budget must be found. One such lower-cost solution is the addition of a single lane to the two-lane, two-way roadway, more commonly known as a passing lane, at selected sites. Although passing lanes have shown great promise as a lower-cost solution, knowledge about their operational effectiveness and more specific design guidelines are limited. This report presents the results of an evaluation of passing lanes in level terrain operating at high traffic flow levels. The operational evaluation of these passing lanes was conducted through the analysis of data collected at one site along the California State Highway System. This evluation was aided by the use of the TRARR model developed at the Australian Road Research Board. In addition to the examination of the TRARR, a brief examination of the RURAL developed at the Institute of Transportation Studies which was experimented with in this project is presented.