Car parking is a tricky one, because even with the best planning and organisation in the world you're dealing with some selfish drivers who seem to expect to be able to turn up 5 minutes before the start and then park yards from the start line. The race I help organise clearly states in the final instruction that the site will be closed 10 minutes before the race starts to ensure that the course is clear of cars, and that there can be 1k walk from car park to start line for the later arrivals. Despite this we've had critical comments from people about the length of the walk to the start and about the fact that they couldn't get onto the site because they were late. And it's often even worse on the way out, when rather then exit in an orderly manner, everybody heads for the exit from all directions at once, taking any possible shortcut they can if they think it will get them 1 car ahead. I remember complete gridlock in the car park after the Windsor Half a few years ago simply because drivers wouldn't follow instructions and turned it into a free-for-all - the marshals gave up and left them to it. I cycle to this race now.