Abstract
Throughput time reduction is an integral part of transportation benefit analysis and traffic engineering optimization objectives. It is for this reason, that a large majority of transportation projects view throughput time reduction as one of their principal objectives. An appraisal of the performance of a traffic intersection complex at Mokola, Ibadan, Nigeria using a conflict intensity approach is presented. This work was carried out in order to quantify the effects of the flyover on the reduction of throughput times of vehicular traffic at the intersection. Conflict intensities were measured through traffic volume counts at various conflict points (through, merging and diverging locations). A floating vehicle equipped with a GPS was adopted to capture throughput times through several trial runs at the intersection. Statistical relationships were established between conflict intensities and throughput times using regression analysis. These relationships served as a framework for simulation for generating travel times (augmented), assuming the absence of a flyover. The results show a statistically significant reduction in throughput times due to the presence of the flyover with p-value of < 0.0001 at alpha level of 0.05 using Wilcoxon-Signed rank test. Specifically, reductions of 40.2seconds (33%) for northbound traffic and 27.6 seconds (28.8%) for southbound traffic were observed. This work has shown that the flyover reduced throughput times. The construction of the flyover is therefore justified and its residual potentials are enormous to handle traffic growth in the area in the near future. Keywords: Intersection Performance, Conflict Intensities, Flyover, Throughput times
Highlights
The traffic intersection is one of such transportation/traffic infrastructures that pose challenges of lowered level of service occasioned by congestion and traffic sprawl especially in the urban centers
This paper focuses on the effect of traffic volume at conflict points within a flyover intersection; with the aim of assessing the effect of the flyover on performance as well as through travel time prediction and comparison
Analysis of Current Traffic Conflict Flow Intensities: The intensities of traffic flow involved at the conflict points at-grade computed based on turning movements using (Equations 1 – 14) and measured throughput times were analyzed with regression to predict throughput time
Summary
The traffic intersection is one of such transportation/traffic infrastructures that pose challenges of lowered level of service occasioned by congestion and traffic sprawl especially in the urban centers. The issue of conflict poses an even more serious problem in developing countries, largely because of nonadherence to lanes and our vehicular mix It is common knowledge in traffic engineering that a typical cross intersection has 32 potential conflict points. It is for this reason that various types of controls such as STOP signs, GIVE WAY, and traffic signals are installed. These controls are primarily designed to assign right-of-way efficiently and safely to conflicting movements (FHWA, 2008). Throughput time was adopted as the performance measure because it incorporates delay experienced by vehicles as well as free flow time
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