Due to their innovative treatment, Unconventional Arterial Intersection Designs (UAIDs) have been developed to alleviate congestion at conventional signalized intersections, in an effort towards the sustainable development of crowded capitals. A methodological framework for economic assessment, however, has not been investigated properly for such designs, particularly under mixed traffic environments. This article aims to outline a methodological framework that can be followed for the socio-economic assessment of such designs. A cost–benefit analysis approach was developed to figure out the different determinants of costs and benefits of an overpass interchange (as a widespread treatment) and two selected UAIDs (as alternative measures). The two studied UAID schemes in this article are Continuous Flow Intersection (CFI) and Restricted Crossing U-Turn (RCUT). Seeking credible results, a set of three signalized intersections in downtown Cairo, Egypt was selected as a proof-of-concept for the developed method. PTV-VISSIM, a simulation-based platform, was utilized to estimate the benefits gained by road users. Our research objectives were to identify, evaluate, and compare the economic feasibility of the different alternatives. Compared to the overpass intersection, we found that the CFI and RCUT designs ensure higher economic efficiency, while mitigating congestion at conventional signalized intersections under heterogeneous traffic conditions.
To alleviate congestions at signalized intersections, Displaced Left-turn Crossovers (DLTs), also known as Continuous Flow Intersections (CFIs) are becoming as prevalent treatments over the past decade in some developed cities around the world. Through the novel solution provided by DLTs, left turn flows could cross the opposing traffic lanes upstream of the main intersection. As a result, DLTs lead to higher capacities, lower delays and fewer crashes. In spite of the extensive preliminary studies focused on the operational performance of DLTs, little research has been conducted considering the coordination of DLTs. In addition, although the considerable sparse works highlighted the DLT intersection, the heterogeneous traffic condition as a dominant operation environment in lots of developing countries has never been estimated. Hence, in order to fulfill the heterogeneous condition needs and considering the coordination of DLTs, the driving force of this study context is developing a real-time demand-responsive signal control system on the solid foundation of the optimization principles. This entire algorithm was built based on developing a mathematical model and utilizing PTV-VISSIM as a micro-simulator based approach. In order to test the proposed algorithm, an inter-process communication and dynamic object creation were provided by employing VISSIM-COM interface and MATLAB a multi-paradigmnumerical computing environment. Although the academic in nature, the proposed algorithm presented in this context could be evolved through a real-world practical application. As a realistic study case, actually obtained data were made available of three signalized intersections located in an arterial corridor in central Cairo, Egypt.
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.
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