Traffic signals have been in use since mankind learned to travel. Yet, little has been done to improve their functioning. The group at IIT Madras gas studied Indian traffic conditions and come up with three counter-intuitive strategies to improve the efficiency of oversaturated traffic flow through road intersections. In a preliminary study, Radhakrishnan, at present an assistant transport planner with Atkins, and Gitakrishnan Ramadurai from the Department of Civil Engineering, IIT Madras, collected data on the variation of headway, which is the distance between the leader vehicle and the following one. Observing vehicles at the traffic signals near three places in Chennai, they found that the distance between two successive vehicles increases with the duration of the green signal. This implies that longer the duration with duration of the green signal, there would be less traffic, thereby reducing the efficiency of the signal. Developing on this study, Dr. Ramadurai arrived at the first strategy: keeping the duration of green signals short enough that the headway reached a saturation value. The second strategy proposed in the paper is to have bottleneck metering along the lines of traffic control on expressways, near entry points and exits. Like highways, expressways have points where traffic leaves or enters through lanes such as T-junctions. These often experience bottlenecks because vehicles merge from different directions, thereby causing ‘turbulence’ in the traffic flow. The researchers collected data from arterial roads in Chennai where a four-lane one-way section of a road merges with a two-way section with two lanes in each direction in a T-junction. They monitored an average flow of different types of vehicles before, during and after congestion for three days. They found that for two-wheelers and cars, there was an increase in flow once congestion starts, whereas, for three-wheelers and heavy vehicles, the flow decreases. Overall, they found a capacity gain at the bottleneck, instead of a capacity drop as expected. Takings such factors into account, they suggest that by placing signals separately for each lane that enters or leaves a bottleneck on an arterial road, and using green signals alternately, a higher throughput or capacity gain can be engineered. The third strategy is based on the observation that two-wheelers have significantly lower headways compared with others, they also have negligible start-up delay. Also in congestion, two-wheelers filter through the gaps and increase overall throughput. The idea is to have separate lanes for two-wheelers close to intersections and an exclusive two-wheeler storage space at the front where they can collect while waiting for the signal to change. A micro-simulation model was used to test this idea. This model showed a reduction in the delay time of about 50% for two-wheelers and an overall delay reduction of 20%.
Tags : #India#Auto#Traffic Reduction