Asda is investing £2.4m in rolling out Techno-trollies', a new system which dramatically slashes the number of trollies stolen from stores. The multiple says that, after a successful trial in six outlets, it is rolling out the technology, designed by US firm Carttronics LLC, to 37 other locations. The trollies have built-in transmitters which pick up radio waves causing them to brake when they reach a boundary around stores. Asda says the system has cut the number of trollies it was losing in the trial stores from four in five to one in 20. However, a spokeswoman for Safeway was unimpressed: "We've been using a similar system in our stores for some time now." Safeway's approach uses electronic perimeter cables which stop trollies if they pass within six feet of them. Sainsbury said it was also trialling the Carttronics system in one store. It has already been using the Gatekeeper system, which works on an induction loop, since 1999, along with the Radlock magnetic strip system. A spokeswoman for Waitrose said: "We have one magnetic system, which uses a strip under a door to disable any trolley which passes over it." {{NEWS }}