QUANTIFYING CROSS-WEAVE IMPACT ON CAPACITY REDUCTION FOR FREEWAY FACILITIES WITH MANAGED LANES

摘要

With the increasing concerns towards environmental impacts and sustainability of roadwaycapacity expansion, transportation agencies are seeking alternative solutions for congestionmitigation. Managed Lanes (MLs) promote person throughput on freeways and managecongestion through improving efficiency. The ML concept therefore has been gaining popularityin the past decades. However, the lack of guidance on performance evaluation of ML facilityposes real challenges for agencies wanting to design and implement the strategy in an effectivemanner. Many MLs are designed to be left-lane concurrent, where vehicles entering the freewayfrom General Purpose (GP) lanes on-ramps, need to cross weave over multiple GP lanes toaccess the ML. These weaving vehicles will have a negative impact on the operatingperformance of the parallel GP lanes. This paper investigates this cross-weaving effect as afunction of different roadway geometric configurations as well as traffic conditions. Amicroscopic simulation model is built and calibrated on the basis of video data collected alongIH 635 in Dallas, Texas. Multiple scenarios are tested to explore the effect of number of GPlanes, cross-weave demand, and cross-weaving length. A set of Capacity Adjustment Factors(CAF) are determined to account for this effect as a function of the above parameters. This studydiscovers that the capacity reducing effect is higher with a reduction in cross weaving length, anincrease in number of GP lanes, or a rise in cross-weave demand volumes. The results arevaluable in evaluating the operational performance of freeway segments in the presence ofconcurrent GP and ML in a Highway Capacity Manual context.