Capacity and Queue Modeling for On-Ramp–Freeway Junctions

Abstract

With reference to the procedure in the Highway Capacity Manual (HCM) 2000 for estimation of measures of effectiveness, a model is proposed to estimate merge-area capacity and to predict traffic dynamics and queue evolution for on-ramp–freeway junctions. The aims of the study are to analyze the behavior of flows within the merge area and to propose a methodology to dynamically estimate the capacity of both ramp and main line according to inflow patterns and to develop a mesoscopic model of merge facilities that allows the prediction of merge-area traffic outflow according to inflow patterns and to estimate traffic queue dynamics. The most relevant finding of the study is a methodology for estimation of the capacity of the merge area referred separately to both the main line and the ramp. The proposed approach could be considered as a link between the HCM hypotheses and those of gap-acceptance theory; the capacity of the competitive streams within the merge area depends on the opposing traffic volumes. The model gives information about traffic flows and queue dynamics (including total delay and maximum queue length). The first results of the application to a case study are briefly discussed, and some further developments are suggested.

Capacity of Freeway Merge Areas with Different On-Ramp Traffic Flow

“…The most widely used method of calculating the capacity of freeway merge areas has been known as the gap-acceptance model [6][7][8][9]. Previous researchers have suggested that gap-acceptance models cannot only provide a scientific approach to studying traffic control maneuvers [10,11], but they can also calculate vehicle queue length on the ramp [12,13] and the service quality of the freeway merge areas [14,15].…”

Revisiting Merge-Influence Area Empirically: Operations Inside Recurrent Freeway Bottlenecks

“…Few efforts, however, were found to specifically analyze merge-area capacity or breakdown. Albanese et al established a dynamic model to estimate capacity of both the ramp and the mainline on the basis of gap-acceptance theories (8). The model used variables such as α (mainline priority) and β (minor-road priority), which need to be calibrated with field data.…”