Performance evaluation of flyovers constructed over levelcrossings in Dhaka city

Abstract

So far eight flyovers have been constructed in Dhaka city with an aim to mitigate traffic congestion, enhance mobility and ensure a reliable transportation system. Although, full grade separation has the potential to eliminate conflicts between rail-road traffic and thereby can reduce both congestion and accidents, out of the eight flyovers, six of them are partially grade separated flyovers. Hence, methodological survey and extensive analyses have been performed incorporating temporal variation (weekday, day; weekday, night; weekend, day; weekend, night) to assess how far the objectives have been met through the construction of these flyovers in Dhaka city. Assessment of classified vehicle data reveals that Banani Overpass has been proved to be most successful in segregating traffic to above-grade facilities (86% segregation) while remaining studied flyovers have performed poorly. Modal assessment revealed that all the flyovers have evidently failed to provide any facilities to non-motorized vehicles and have instead inclined private car and smaller sized vehicles. However, Jatrabari-Gulistan Flyover have been observed to provide maximum usage to the public transport (48 % bus travelling above grade) while remaining are performing very poorly. Assessment of travel speed and free flow speed revealed that Banani overpass (average vehicle travel speed of 36 km/h above-grade and 17 km/h at-grade) has been proved to be most successful in facilitating mobility. Remaining flyovers are performing at their worst. Assessment of queue length and accident data revealed that, Khilgaon flyover has shown the maximum queue length (882 m) and compared to previous studies, Jatrabari-Gulistan Flyover has shown highest increase in congestion rate (168% within last two years). Hence, these two flyovers are the worst in mitigating traffic congestion. Overall analyses have revealed that the flyovers constructed over the rail-road conflicting points have not been generally successful in segregating traffic to above-grade from at-grade, providing any facility to non-motorized vehicles and public transport, enhancing mobility in urban road, reducing perennial conflicts between rail-road traffic and mitigating traffic congestion in Dhaka. Rather, construction of flyovers is reducing the at-grade road carriageway, making public transport unpopular, shifting traffic congestion from one location to another and diminishing the future scope for public transit oriented development. Finally the study puts forward suitable recommendations from the light of the study findings to alleviate the associated problems and guides towards a sustainable solution.