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 I-8 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. Twelve different analyses were conducted with existing
traffic conditions and projected traffic volumes till year 2022. 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 reduced 30% on average and has positive impact on LOS of
few turning movements. 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.
