We have "emissions" tests, so that if it gives off too many particulates in the exhaust, it has to be fixed or junked. Otherwise, we can buy and sell just about anthing that moves.
The emissions test is part of the NCT, an understandable test for urban areas, but there are other tests for 'road-worthiness', which means too many faults mean simply getting a new car.
It's a bit crazy - I believe older cars are better for road safety, simply because they aren't as well tuned, therefore slower - speeding and overtaking are the biggest killers on roads.