Safety has a price and, though expensive, deliberately crashing cars remains a good way of testing an automobile's safety features. However, there is a new crash simulation facility that promises a decrease in the number of cars destroyed during tests. Developed by the German company Instron, and recently installed at BMW in Munich, the non-destructive method relies on reverse acceleration. To work, the car mounts on a rail-borne slide. A hydraulic catapult accelerates the car backwards, producing 70g shock levels. Controlled by the Siemens PC-based SIMATIC WinAC, which communicates with the system via the Profibus-DP and AS interfaces, the process uses reference traces of the motion parameters derived from actual destructive crash tests. The only difference is that they are "replayed" in reverse. Optical and electrical sensors, mounted on the slide, record performance of the car's safety equipment. Not only does the system save money and metal, it allows more frequent testing. Contact Juergen_Kraemer@instron.com or visit www.instron.com/ist. For information about Siemens control equipment, Enter 647.