Bandwidth Maximization Approach for Displaced Left-Turn Crossovers Coordination under Heterogeneous Traffic Conditions

Abstract

As one of the UAIDs (unconventional alternative intersection designs), DLTs (displaced left-turn crossovers) have been presented to mitigate traffic congestion. Although, qualitatively and quantitatively isolated UAIDs outperform their conventional counterparts, there is no simplified procedure to consider the DLTs coordination. Hence, this research investigates the coordination of consecutive DLTs under heterogeneous traffic conditions. To achieve the optimal coordination and provide an efficient coordination control, a bandwidth maximization progression approach was used. Seeking the optimal offset for each pair of consecutive intersections to guarantee the green bandwidth waves along the coordinated corridor, a mixed-integer linear program was adopted. The optimization problem was formulated and solved based on the standard branch-and-bound technique. As a real-world study case, data of three typical intersections located in an arterial corridor in Cairo, Egypt was used. PTV-VISSIM as a microsimulation platform was employed to simulate and evaluate the different signal timing plans. However, to represent the heterogeneous traffic characteristics as close as possible to the reality, different simulation parameters were tuned and validated carefully. The results emphasized the undoubted improvement of coordinated DLTs by different operational performance indices. The total travel time, average delay, the number of stops per vehicle were obviously improved.

Cost–Benefit Analysis of Unconventional Arterial Intersection Designs: Cairo as a Case Study

“…Both the vehicle type and used fuel type affect the cost savings associated with CO 2 emissions due to a reduction in excess fuel consumption. The standard emissions rates for diverse vehicular modes were used to calculate the CO 2 emission due to congestion in Cairo; namely, one liter of consumed gasoline or diesel by passenger cars was considered to produce 2.40 and 2.41 kg of CO 2 , respectively [5]. Attention should be paid to converting the volume units of the wasted diesel and gasoline annual amounts in liters to mass units (i.e., in kg) before substituting into Equations ( 9) and (10), bearing in mind that 1.0 L of diesel weighs 0.832 kg, while 1.0 L of gasoline is 0.77 kg.…”

“…The annual cost due to the reduction of the total travel time was calculated according to the method developed by the Texas Transportation Institute [19] and followed in other previous studies [5,20]. The total travel delay time on a road network (i.e., the amount of extra time that traffic takes due to congestion) was estimated using Equation (11).…”

“…Based on its hypothetical basic foundation, the NPV was estimated according to reductions in future values with respect to the present ones by utilizing a social discount rate, as shown in Equation (13). Following similar previous studies [5,20,23], we assumed that the lifespan of the proposed intervention is 30 years for super-structures elements and sidewalks, while it is 10 years for signal heads, detectors, and control units. Thus, the net present value of each cost and benefit of each proposal can be calculated over the lifespan of the project.…”

“…We considered three conventional signalized intersections-namely, Abass Al-Aqad (AA), Makramm Ebied (ME), and Al-Tairan (AT)which have four-leg directions with divided three-lanes-per-direction streets, as shown in Figure 5. Aggressive driving behavior, however, causes non-lane-based flow, resulting in low LOS at the studied intersections [5][6][7][8]24]. On the other hand, operational regulations restrict direct left-turns through traffic of southbound approach, in order to alleviate the congestion in the studied intersections (see Figure 5).…”

“…This study is a part of an ongoing research project investigating the applicability of UAIDs under heterogeneous traffic complexities, in order to gain a better understanding of the performance, vulnerabilities, and limitations of such designs [5][6][7][8]. The main objective of this paper is to develop a methodological framework that could be followed as a socio-economic assessment approach for UAIDs.…”