The Doncaster, UK Road Safety Education Unit has developed a plan to recruit activists to become "mobile speed bumps" in a "Community Pace Car" program. Residents who who sign up receive a distinctive bumper sticker that identifies them as individuals who have agreed to adhere strictly to the posted speed limit and to block anyone who attempts to speed past. Other areas that have tried this method of "traffic calming" have also employed large municipal trucks in the traffic throttling effort.

Some safety experts are skeptical and suggest the program will prove more dangerous than helpful.

"Road safety works best when drivers co-operate together and adjust their speed to suit the hazard," said Paul Smith, founder of the Safe Speed road safety campaign. "This vital behaviour is being gradually, inexorably and dangerously replaced with a 'driving by numbers' approach. As a nation we are becoming obsessed with speed limits -- and that's a very bad thing."

"Many speed limits are now set against government advice and too low for driving conditions," adds Mark McArthur-Christie with the Association of British Drivers. "Where this is the case, following drivers bunch behind the lead car with greatly reduced separation distances. When the car in front brakes, the cars in the column can't stop in time. We're concerned that acting as a Pace Car is putting yourself at risk of a rear-end collision."