Posted By Paul Grady Hi. A SIMRET meter is a basic brake efficiency testing device. It is not permanently fitted to the vehicle - as it is a portable device (it comes in a box). As its basic, its more of an indicator than an absolute way of determining how good your brakes are. Under PUWER you need to do adequate maintenance. Under Road Traffic legislation, you must have an MOT, etc. As an aside, if there were no pads left on the vehicle at all, i.e. metal to metal contact, when brakes were applied it may still stop in the given response time. Therefore it would pass. This is why a visual is always completed first. If you go to the Vehicle Inspectorate testing depot's, they'll show you a SIMRET.