Abstract:
Signalized intersections are the most complex locations in urban road network system. The operational conditions of intersections profoundly affect the well-being of the movement of goods and passengers. The operational quality of an urban road system in Pakistan gradually deteriorates due to increase in traffic volumes and an expectation of higher level of service (LOS). A well-planned, efficient and prudent scheme is necessary to assure a safe and smooth operational condition of road system at all times. A number of approaches to evaluate the performance of signalized intersections are recommended by various transportation entities, and implemented in cities with desirable outcomes. This study investigated various factors affecting the operations on at-grade urban signalized intersection G-11 on Kashmir Highway Islamabad. The factors considered were, (a) capacity analysis, (b) volume/capacity ratio, (c) delay analysis (approach delay, control delay), (d) existing level of service (LOS) and (e) intersection capacity utilization (ICU). In order to find the peak hour volumes and peak hour factors for selected signalized intersection, traffic counts were carried out using Jamar Traffic Data Collector (TDC) on weekdays and weekends. Six different analyses were conducted with existing traffic conditions on existing geometry and improved geometry. Furthermore, data were analyzed with existing and improved intersection geometry. It is concluded that capacity of intersection increased as v/c ratio reduces after optimization. The signal controlled delays were not significantly reduced on existing geometry after optimization due to very high traffic volumes on Kashmir Highway but improved geometry with five lanes each side on east and west bound reduced control delays by 25 percent. The overall intersection LOS did not improve with various iterations. Similarly, intersection capacity utilization (ICU) remains the same before and after optimization. In the short term, LOS can be improved by increasing the number of lanes. Whereas, in long term grade separation of at grade signalized intersection is recommended.
