New wireless system reduces traffic congestion

MIT researchers have developed a new system that can wirelessly route drivers around congested roadways.
The new system, dubbed RoadRunner, developed by Massachusetts Institute of Technology (MIT) uses GPS-style turn-by-turn directions to route drivers.
In simulations using data supplied by Singapore's Land Transit Authority, the researchers compared their system to one currently in use in Singapore, which charges drivers with dashboard-mounted transponders a toll for entering congested areas.
The Singapore system gauges drivers' locations with radio transmitters mounted on dozens of gantries scattered around the city, like the gantries used in many US wireless toll systems.
RoadRunner, by contrast, uses only handheld devices clipped to cars' dashboards. In the simulations, it yielded an 8 per cent increase in average car speed during periods of peak congestion.

For purposes of comparison, the MIT researchers restricted themselves to road-access patterns dictated by Singapore's existing toll system.

Modifying those patterns - encouraging or discouraging the use of different stretches of road - could, in principle, lead to even greater efficiency gains.
Jason Gao, a graduate student in electrical engineering and computer science who developed the new system together with his advisor, Professor of Electrical Engineering and Computer Science Li-Shiuan Peh also tested the system on 10 cars in Cambridge, Massachusetts.
While 10 cars is not enough to dramatically affect local traffic patterns, it was enough to evaluate the efficiency of the communications system and of the vehicle-routing algorithm, researchers said.

It also provided reliable data about the system's performance for use in simulations.
Urban toll systems like the one in Singapore designate certain regions - with gantries at every entry point - as prone to congestion.
Drivers are charged a fee for entering any such region, so they have an incentive to avoid it. The fee fluctuates over the course of the day, according to historical traffic data.
RoadRunner, by contrast, assigns each such region a maximum number of cars. Any car entering the region must acquire a virtual authorisation that Gao and Peh call a "token."
If no tokens are free, RoadRunner routes the car around the region using turn-by-turn voice prompts.

The version of RoadRunner used in the Cambridge tests was largely decentralised: A car leaving a region would wirelessly announce that its token was available, and a car seeking to enter the region would request it.
The system used a wireless standard called 802.11p, a variation on Wi-Fi that uses a narrower slice of the electromagnetic spectrum but is licensed for higher-power transmissions, so that it has a much larger broadcast range.