Comparison of Alternative Junction Designs For Light Rail Transit Grade Crossings

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Light rail transit is a relatively new mode of transport for Ethiopia. Hence, rigorous research needs to be done in order to identify and work out flaws in the system. Most of the road-rail intersections within Addis Ababa LRT corridors are built as grade separated intersections. However, certain intersections such as Sealite Mehret and CMC roundabout meet the LRT line at grade. Research done up to now on these areas, points out significant problems with respect to traffic congestion. The main causes of congestion in this area that are related to the LRT line are: frequent LRT crossing and interruption of traffic flow, high pedestrian volumes at stations near the roundabouts that impede entry and exit flows, lack of U turn areas along the LRT corridor, which transfers high volumes of U turning vehicles to the roundabouts, which in turn adds to congestion of the roundabouts. Performance evaluation of the roundabouts under current traffic conditions was done during peak and off – peak periods. Results indicate approach delays of over ten minutes for both locations during peak periods. However, during off – peak periods the roundabouts perform above level of service C. The goal of this study is to propose alternative solutions to mitigate each cause of congestion and to see if adequate performance can be achieved without grade separation at the selected locations: Sealite Mehret and CMC roundabouts. In order to fulfill this goal necessary data were collected at the study areas. Then the alternatives were designed and modeled using VISSIM simulation software. The alternatives considered are signalized intersection, signalized roundabout, installation of pedestrian signals and diverting U turns to other locations. Comparing these alternatives based on queue length, travel time, intersection delay and level of service under current traffic conditions, showed that the best alternatives for both locations are signalized roundabout and signalized intersection. Up on comparing signalized roundabout and signalized intersection alternatives under forecasted traffic conditions, analysis results showed that both options have similar travel times and delay. Both alternatives are viable options. However, since signalized roundabout alternative provides the option of functioning as a normal roundabout during off peak periods, and reduces risk of right angle crashes, signalized roundabout is preferred.



Signalized roundabout, LRT grade crossing, VISSIM