COMPARATIVE EVALUATION OF ROUNDABOUT CAPACITIES UNDER HETEROGENEOUS TRAFFIC CONDITIONS AT PATEL CHOWK AND RACE COURCE IN DELHI, INDIA (A CASE STUDY)

This paper addresses the MIXED TRAFFIC CAPACITY and the analysis of GEOMETRICAL PARAMETERS of roundabouts at PATEL CHOWK (Raundabout-1 or R.D1) and RACE COURSE (Raundabout-1or R.D2) present in the heart of DELHI. The entry of mixed traffic of vehicle in peak hour was observed for one hour at both roundabouts termed as Circulating Flow Capacity or Volume Capacity (Qc) noted down in terms of passenger car unit per hour (pcu/hr) or vehicle per hour (veh/hr). The geometrical parameters of both the roundabouts are noted down, through which the Entry Capacity or Practical Capacity (Qe or Qp) of the roundabouts is determined using U.K CAPACITY MODEL and IRC CAPACITY MODEL. The ratio of Circulating Flow Capacity by Entry capacity is called as DEGREE OF SATURATION (DOS) which should be less than 0.85, for the smooth flow of traffic without any congestion to avoid queue of traffic and delay in time. During the analysis it was found that most of the legs of both roundabouts are in good shape and are in under control i.e. their Circulating Flow Capacity (Qc) is less than Entry Capacity (Qe) and their degree of saturation is less than 0.85 except few legs, for north leg of R.D1 the Qc >Qe { Qc=2452 veh/hr & Qe=1617 veh/hr } and DOS=1.51, also for east leg of R.D2 Qc is very close to Qe { Qc= 1536 veh/hr & Qe=1550 veh/hr } and DOS=0.94. Rest all other legs, six out of eight legs of the roundabouts are in control. Also at R.D2 for north leg, entry width (e1) & approach half width (v) is coming out to be very less compared to entry width of other legs. {e1=6.1m v=5.8m}. Also for R.D1 for leg north, east & south length of weaving section (L) > four times the width of weaving section (4W). {Leg N, L=60.5m > 4W=57.36m .Leg E, L=59.54m > 4W=57.64m. Leg S, L=60.19m > 4W=55.64m} will cause road accident because greater length of weaving section causes over speed. Rest all other geometrical parameters of the roundabouts are in good shape and are in permissible limits. Overall performance of both the roundabouts under mixed traffic is good and geometrical parameters are within permissible limits. Further future study is required for analysis of capacity by Gap Acceptance Model which is based on driver behavior and depend on queue length & delay time of traffic.