Vash: Look at it this way. He didn't go out riding that day to escape from the cops. It was an unplanned pursuit. A very likely situation that he was in was that he had incriminating evidence on him (like pot, or a suspended license, or something), and he just took a risk going out riding. When a cop tried to stop him (for whatever coincidential reason), he ran. Probably a spur-of-the-moment decision with no prior thought put into it. Now, he's on a bike... riding extra fast, knowing the cops are on his ass. I don't know about you, but I'd be nervous as shit! My brain would be in the fight-or-flight mode (flight, obviously), and no rational reasoning would be going on. Some people just do good under pressure, others don't. He probably just didn't.