MANCHESTER, England (Feb. 20)—Dunlop GRG has developed an inflatable traffic road hump designed to give a smooth ride to drivers who obey speed limits and certain emergency vehicles. Currently being tested in London, the Dunlop Transcalm is an inflatable rubber unit fitted with an air valve that controls the rate at which air escapes as a vehicle drives over. The device is designed to deflate for large emergency vehicles and motorists going below a set speed limit, according to Dunlop GRG. But at higher speeds the valve closes so the hump presents a rigid obstacle to speeding motorists, it added. "The concept was based on the basic premise that responsible drivers should not be punished for travelling within the speed limits," according to Mike Armstead, chairman of Dunlop Transcalm. Dunlop GRG was part of UniPoly S.A. until early 1999, when it was spun off along with Greengate Polymers to management.