If I've heard it once, I've heard it a thousand times: people with autism think differently than the rest of us. They have more trouble understanding social cues and context but less trouble understanding patterns.
We're starting work with a behavioural therapist in preparation for a new round of intensive behaviour therapy for Alex. She gave us one of those insights which seems blindingly obvious in hindsight but which I never came close to on my own.
If you have a child who bolts, never let them precede you anywhere.
Don't let them go out the door first. Don't let them run ahead to the park. Don't let them head out to the car while you watch from the doorway. Always go first and then give them a clear signal that it is okay to follow.
A child with autism won't understand why sometimes it's okay for them to go ahead of you and why sometimes it's not. From their perspective, there may not be a difference between going out the door by themselves for a family excursion and going out the door by themselves in the middle of the night because they saw a cool car.
Consistency is the key but it's hard for parents (certainly for me!) to grasp what might be linked in their child's mind. To us, there's a clear difference. To them, it's the same.