The lane closures caused by the work zone at the approaches create a negative impact on the operational effectiveness of the signalized intersections. This paper presents an innovative design for intersections with work zones to improve the intersection's practical capacity. In this design, the lanes in the leg with work zone can be used dynamically as approach and exit lanes during different periods of a signal cycle by using the pre-signal. An optimization model for an optimal geometric layout and signal timing design is built to capture real-world operational constraints, including the lane assignment, the signal timing of the main signal and pre-signal, the distance of the mixed-usage area and the transition area, and the degree of saturation restriction.A case study and extensive numerical analysis demonstrate the effectiveness of the prospective design as compared with conventional designs under different geometric layout and traffic demand situations. Overall, the proposed design can lead to an increment in the practical capacity of the intersection with a work zone (by up to 30%) and reduce the average vehicular delay accordingly (by 50%) without necessitating an expansion of the intersection. The results show that the promising application of the proposed design when the length of the work zone is less than 160 m.
The intersection with special width approach lane (SWAL) is a newly proposed unconventional intersection design. A microscopic traffic flow model was proposed for describing the operation of vehicles at signalized intersections with SWAL. The operation process of driving on the SWAL was divided into four segments, including entering segment, transition segment, special width lane segment, and exiting segment. The car-following and lane selection behaviours of vehicles in these segments are analysed. The parameters used in the model were calibrated using the field data collected in Germany. The proposed model was realized in a time-discretized simulation. The sensitivity analysis of geometric, traffic, and signal factors were conducted. The results show that for the car-following behaviour, the passenger cars on the narrowed lanes cannot drive as efficient as on the normal width lane. For lane selection behaviour, it mainly depends on the distance between the two nearest vehicles in front on the two narrow lanes. The effectiveness of the SWAL depends on whether it is long enough to accommodate the queuing vehicles, which is a combined result of the layout design and the signal timing.
The special width approach lane (SWAL) is a newly proposed unconventional design, whereby a wide approach lane is divided into two narrower lanes. The design entails the use of a single lane by two passenger cars or one heavy vehicle. Such design has been applicated at signalized intersections of Karlsruhe, Germany. This paper focuses on the saturation flow rate analysis since most existing studies on such design rely on the default highway capacity manual (HCM) values. Saturation flow rate data was collected at four SWAL design based signalized intersections with procedural steps of the HCM 2010 using the video camera. The two-sample t-test was performed to explore the potential influencing factors, and then the non-linear regression analysis was conducted to estimate the saturation flow rate of SWAL. The proposed model can effectively depict the saturation flow rate with lane marking, presence of cyclists, and rainfall being the influencing factors. The overall accuracy of the proposed model is about 95%. The results indicate that the three influencing factors are independent of each other. The existence of cyclists and rainfall lead to a decrease in the saturation flow rate, while the lane markings can improve the saturation flow rate. Moreover, the SWAL works well in Karlsruhe, Germany. The model predicts a base saturation flow rate value of 1652 pcu/h/ln, which is plausible with comparison of the base saturation flow rate recommended in the German Highway Capacity Manual.
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