Be it brakes, seats or ignition lock, before any model goes into series production, components must go through months of testing in Technical Development (TD). To perform these tests, the teams build models known as prototype carriers. Between 2009 and 2014, the number of these at the Wolfsburg factory rose by 0ne-third to around 8,200. One reason for this growth was the expanding model portfolio. But an analysis in fall of 2014 showed that these prototype carriers have been used infrequently or, for long periods, not at all.