Friday, March 2, 2018

Review: 'Latent heat' of traffic

Paper Review: Latent heat of traffic moving from rest, S Farzad Ahmadi, et al.,  New Journal of Physics, 19.113034, IOP Publishing Ltd. This paper analyses the behavior of vehicles when those are stopped/started at traffic junctions and the resulting delay. Using a drone camera and drivers queued at a red light on a Smart Road, it shows that vehicles jamming into a ‘solid phase’ at stoppages do not increase the efficiency of resumed flow. There exist a delay, akin to latent heat, inherent to phase-transitions from free flow of traffic to the flow waiting for the signals, and vice versa, at each traffic junction.  The larger bumper-to-bumper spacings that cars maintain when driving at speed can therefore be largely preserved at stoppages too, to minimize the risk of rear-end collisions with no loss in travel efficiency.
I think the paper effectively suggests a new and changed approach to design of traffic control elements. Why can't we have the traffic signals distributed to all drivers/vehicles? The vehicles being brought to a stop/start in response to the appropriate signal, wherever the vehicle is? Won't this fit the future, the new developments in propulsion, cruise control and autonomous vehicles is certain to bring?