oa Unsignalized Intersection: Assessment, Forecast And Performance Measures

Vehicles at Qatar university road networks are subject to pass through multiple roundabouts and intersections in order to reach their destination. Since the traffic volume is relatively low, unsignalized controlled intersections are used to regulate the flow of vehicles (sign-controlled) .T shaped intersections and multiple lane roundabouts are utilized throughout Qatar University closed loop system. This study has been conducted to measure the current performance of some unsignalized intersections at Qatar University roads. Two roundabouts and one TWSC intersection were selected for the study. The methods presented in the Highway Capacity Manual (HCM 2000) were employed in this study and were used to compute the various approaches and movements capacities and the related performance measures .e.g. Control Delays (s), Queue lengths (veh ) and Level of service (LOS). To this end we will base our capacity analysis on Gap acceptance method and on simple, empirical, lane-based, regression model for multiple lane roundabouts. Data inputs collected for the selected method involved the critical traffic volumes (veh/hr) which occur in the peak hour .15 peak minute flow rates were recorded to obtain the peak hour flow rates. In addition the methods were used to make future projection of the capacities and the related performance measure based on forecasted demand in 2022. The results show that the current performance of the roundabouts is satisfactory for which the Level of service was graded A for all approaches in the two roundabouts given that the computed delays never exceeds 10 s / vehicle in any approach. The current results for the roundabouts coincide with the actual performance of the intersections where very little delays are encountered while driving and very short queues are formed during the peak hour. Regarding the T intersection the performance of the Left turn of the major street was found satisfactory and was graded A while the performance of the shared lane of the minor road was graded C. Based on forecasting results, the increase in entry and conflicting flow rates have resulted in decreasing the expected capacities of the various approaches on the studied intersections. In general for the roundabouts no significant difference in performance is to be experienced in year 2022 when current demand is expected to experience over 50 % increase and still the performance will be satisfactory. The same conclusion was drawn for the Left turn movement from Major Street that no major difference in performance is projected in future. But this conclusion was not applicable on the shared lane where it was very much affected by the increase in demand and the performance has rapidly dropped from its current level.