Measuring turbulence distance of acceleration lanes

Turbulence distances are a major design criteria in the design of new freeways and the modifications of freeways. In the Dutch freeway design guideline (NOA) turbulence distances are applied to determine the minimal distance between on-ramps and off-ramps to enter and exit the freeway, or to switch from the one freeway to the other, and lane drops. However, the origin of these values are unknown. In the meanwhile, these values are applied, while the pressure on the infrastructure system is increasing. Hopefully these values can be decreased by measuring the effect of discontinuities on the traffic flow. In this thesis an innovative method is developed to measure the general macroscopic effects on the mean speed, lane flow distribution and lane density by combining induction loop data of multiple freeway acceleration lane locations. This thesis focuses on the effect of acceleration lanes on the traffic flow by comparing the data of acceleration lanes with the data of locations without discontinuities. With this method little effects are found on the mean (lane) speed. In the lane flow distribution and lane density effects of the acceleration lane on the traffic flow are found. On the outside lane decreases the fraction of the flow and lane density just upstream of the acceleration lane. Further downstream, the fraction and lane density increases strongly until just downstream of the acceleration, and decreases back to the "normal" level. On the median lane the opposite behavior is found. Based on a rough estimation the effect of the acceleration lane is found 500 meter upstream and 800 meter downstream of the acceleration lane.Transport & PlanningCivil Engineering and Geoscience