Traffic monitoring gets smart

OhioStateUniversity engineers have developed software for road traffic control boxes that can detect and notify authorities of accidents and congestion at a much lower cost.

Benjamin Coifman, associate professor of civil and environmental science and geodetic science at OhioState, said that over the last few decades, US transport agencies had installed loop detectors to monitor traffic at key points on the road network.

The car-sized wire loops buried in the tarmac effectively act as metal detectors. When a vehicle passes over a loop, the detector sends a signal to a computer in a control box at the side of the road.

The controller may simply count the number of cars that pass by and calculate average speed, or it may actively control traffic, by operating a traffic light on a motorway slip road, for instance.

The main cost of using such devices is the that of sending electronic signals between them and the transportation centre that is doing the monitoring. Normally, controller boxes transmit their data very frequently, some as often as once every twenty seconds.

Coifman and former graduate student Ramachandran Mallika wrote software that enabled the controller boxes to detect traffic incidents and get important messages back to the traffic control centre using a fraction of the bandwidth that was previously required.

Initial results show that their software achieved better than 90 per cent accuracy in reporting traffic conditions at the interchange between two busy interstate roads in ColumbusOhio, using up to 200 times fewer signals than before.

Instead of sending all of the data all of the time, the new software infers road conditions based on traffic patterns. It determines whether conditions are critical enough for an alert to be sent to a state transportation authority. Otherwise, it sits quietly and leaves the communication channel free.

The approach is more efficient, because the controller boxes only send signals to the control centre when absolutely necessary, which reduces communications costs. The transportation authorities would only need to electronically ‘ping’ a quiet station once in a while, to make sure it was still working.

Between pings, the station would store non-critical data, such as the traffic counts that authorities use to determine if a road needs resurfacing, to be retrieved later.