Throughout a racing season there is constant, relentless pressure on the designer to keep making design improvements. But there is a limit to what can be achieved with any car design, before a jump has to be made to basically a new design, an innovation. As Gordon Murray says, ‘Given the situation and the pressure at any one time, you do get to the brick wall...I mean you're doing all these normal modifications, you know you can't go any quicker, you need to make the step forward.’
In the midst of the pressure, the fervour, the panic, he ‘used to get breakthroughs, I mean I used to get like suddenly a mental block's lifted.’
That's what is great about race car design, because even though you've had the big idea - the “light bulb” thing, which is fun - the real fun is actually taking these individual things, that nobody's every done before, and in no time at all try and think of a way of designing them. And not only think of a way of doing them, but drawing the bits, having them made and testing them.
Perceptual: "They couldn't figure out what to do next", "they couldn't find the feature", "they didn't know they could click that button..." etc.
Domain-specific: "We need a way to jump back here because in their workflow this happens..."
In general, usability testing only catches type 1 perceptual problems. Because in those tests you take people out of the real world and assign them tasks. Usability testing doesn't catch domain-specific problems because they only come up in real life use.