Farritor says they can open and close traffic lanes faster and more safely than humans. The markers are delivered to the roadside by a specially equipped truck, from which an operator controls their deployment using a laptop computer. Each fleet of robots is made up of a lead robot or "shepherd", which is equipped with a Global Positioning System satellite navigation receiver, plus a number of less expensive "dumb" units. The laptop screen displays an image of the road, captured by a camera mounted on top of the truck. Using software developed by Farritor's team, the operator marks on the screen where the barrels should be placed. From this the software calculates the GPS coordinates of the point where the shepherd should be placed, and this is sent to the shepherd via a radio link. The shepherd takes up its position, and also tells the other markers, by radio, where to go. They then use dead reckoning- counting how many times their wheels turn, for instance- to work out their position. Each robotic base has two electric motors, powered by a 12-volt lead-acid battery, which drive two 20-centimetre-diameter wheels.
This allows the robot bases to turn on the spot, and travel at up to 1.3 metres per second- about walking pace. The shepherd checks its "sheep" are in the right place using a laser-based radar (or "lidar") system to correct any positional errors. The lidar also has a safety role. If a marker is detected consistently straying out of position, the shepherd moves it out of harm's way and shuts it down. On a test track, Farritor and his team used a swarm of six markers to form wedge-shaped lane barriers. He says they were able to achieve an accuracy close to that of humans. "Our tests proved these robots can work in teams to provide traffic control," he says. "Deploying and retrieving highway markers on open roads is hazardous so the robots will reduce risks for workmen," he adds. Farritor says the next steps will be to improve the graphical positioning software on the PC and to cut the cost of the cones so the idea can be commercialised. The prototypes cost $700 each, but the team aims to reduce that to $200 by using cheaper motors. "At that price I believe the savings will mean it will still be affordable if one dies in the line of duty," he says. Andrew Howard, head of road safety for the AA Motoring Trust in the UK, welcomed the idea. "They could be a big help on lanes that are shut during quiet times and reopened during peak traffic periods," he says.
Author: Max Glaskin
New Scientist issue: 1 May 2004
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