The plaintive plea to the traffic cop is the same the world over: 鈥淪orry officer, I didn鈥檛 know I was speeding.鈥� But drivers may soon have to come up with a better excuse. A new electronic driver鈥檚 assistant will detect road signs and warn drivers not to ignore them.
The Australian invention is part of a global effort to make drivers more aware of road signs, especially those concerned with safety. Eventually, GPS-based systems could entirely replace road signs, but until then, ideas like the new driver assistance system (DAS) developed at the National Information and Communications Technology Australia (NICTA) lab in Canberra may help.
DAS uses three cameras: one to scan the road ahead and a pair to monitor where the driver is looking. The road camera is mounted on the rear view mirror and a 鈥済aze monitoring鈥� pair are set on either side of the instrument panel on the dashboard.
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Images from the cameras are fed to a computer system fitted behind the dash. Software on the PC detects road signs and works out where the driver is looking. The speedometer is also connected to the computer, so the system always knows how fast the car is travelling.
Symmetrical shapes
The software scans the video pictures and detects road signs by recognising their symmetrical shapes: rectangles, diamonds, octagons or circles. Once a sign is detected, the image is compared to a list of signs stored in the computer鈥檚 memory. If it recognises a stop sign, the computer checks if the car is slowing down.
The computer uses a commercial package called FaceLab to analyse images from the stereoscopic cameras and work out where the driver is looking. If the driver appears not to have seen a sign, and the car鈥檚 speed does not change, an alert is issued, says Nick Barnes, one of the developers at NICTA.
NICTA鈥檚 team will tell the International Conference on Intelligent Robotic Systems in Sendai, Japan, this week that in preliminary tests DAS performed 鈥減retty well鈥� even at high speeds. Full-scale road trials, due to begin soon, will test the system with many more types of road signs.
Former NICTA team member Gareth Loy, who is now at the Royal Institute of Technology in Stockholm, Sweden, says sign detection is a tough engineering problem. Previous approaches have tried sensing the colour patterns in signs.
Cluttered scenes
But varying lighting conditions makes this difficult. NICTA鈥檚 鈥渟ymmetry seeker鈥� makes detection easier in a cluttered scene regardless of the lighting, he claims.
However, there is a danger that sign detection could become annoying, warns Andrew Howard, head of road safety for the UK鈥檚 Automobile Association, especially on routes where the driver is familiar with the signs. Barnes agrees but says the system will not alert the driver if they do not look at a sign, only if they ignore the limit.
He predicts that working systems will have overrides or variable sensitivity. 鈥淚t would be possible to set the system to be a little more tolerant of driving slightly over the speed limit,鈥� he says.
Meanwhile, projects aimed at replacing road signs with roadside radio beacons, or GPS-based information systems that alert drivers to road rules, continue. Though Barnes says this will take many years, some campaigners cannot wait to see the end of road signs.
The Campaign to Protect Rural England, for instance, is protesting about the increasing number of signs cluttering English villages. But Australia, has a different problem. 鈥淲e don鈥檛 have that many road signs, so we need all the help we can get in finding them,鈥� Loy says.
