Browse Publications Technical Papers 2020-01-5157
2020-12-30

A Novel Model for Traffic Flow Prediction at Secondary Separation Exit Ramp 2020-01-5157

The secondary separation exit ramp is designed for traffic stream splitting for a second time after entering the off-ramp, which is common and brand-new type of ramp. However, few studies have focused on the traffic flow estimation of this kind of ramp that is the first step for calculating its capacity. Therefore, it is vitally important to accurately predict the flow in the secondary separation exit ramp. On the basis of subdividing the type and refining the structure of this facility, this study investigates around 114 different ramps and collected more than 30,000 pieces of data of volumes, speed, geometric characteristics, etc. from PEMS. Afterwards, learning from HCM2016 practice on the vehicle operation status of the exit ramp, the research team explores the influence of various factors, such as flow of each section, on the flow of outside key lanes of secondary separation exit ramps. Then, the flow estimation models of the outside key lanes are established respectively for six-lane, eight-lane and ten-lane freeways, and the prediction accuracy is compared with the accuracy of the HCM2016 model. The results elaborate that the applicability of the model is quite good, and it reflects the linear relationship between the rightmost key lane flow and the mainline flow, as well as the logarithmic relationship between the outside key lane flow and the right/left-turn flow. The form of the proposed flow estimation model of multilane secondary separation exit ramp is unified. Furthermore, the prediction accuracy of the proposed model is 0.97 to six-lane freeways, 0.93 to eight-lane freeways, 0.90 to ten-lane freeways, which are significantly higher than the accuracy of HCM2010 model (0.86, 0.31, 0.70 respectively). The results are expected to be applied to complement the contents about diverge segments in Highway Capacity Manual.

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