ECONOMIC ANALYSIS OF INTERMITTENT PASSING LANE GEOMETRIC DESIGN FOR LOW VOLUME RURAL HIGHWAYS

摘要

The purpose of the study is to justify the implementation of intermittent passing lanes onrnrural two-way, two-lane highways where passing opportunities are limited. In this study, passing lanernlength and the distance between passing lanes are correlated to two major parameters: Average DailyrnTraffic (ADT) and percentage of trucks. Passing opportunities are modeled to decrease with increasingrnoncoming traffic. In addition, as ADT increases, delay timesaving increase. Also, the increase in thernpercentage of trucks creates more delay which results in a need for more passing lanes. A highrnpercentage of trucks also causes operational problems in terms of reduced level of service, increasingrnpassing attempts, aborted passes and driver frustration. An economic analysis is performed to reveal thernbenefit-cost ratios (B/C) for different situations. Reduction of queues and enhanced passing opportunitiesrnyield travel timesaving and a predicted reduction in accidents. Taken together, these output parametersrnform the benefits accrued by implementing Super Two highway design. The study found that time savingrnbenefits alone are not adequate to justify the construction of the Super Two section (approximately 15% ofrnthe savings are contributed by the time saving benefits). However, when accident cost saving benefits arernadded to the model at constant truck percentage (10%) and with varying ADT, the B/C ratio increases withrnincreasing ADT levels. The Super Two section can be justified starting from an ADT level of 2500.rnAdditionally, if the new geometric cross-section can be implemented without the need to widen the road,rnSuper Two can be warranted at much lower ADT levels.publication.