And in case the 12 sec rule or whatever other rule you use fails you, remember to stand up just before impact. This apparently assists you to go over the obstructing vehicle rather than taking the direct route through it.

Saw that little gem in a bike mag years ago. I'm in no hurry at all, however, to be able to advise from personal experience...

There are obvious limitations of course, this isn't going to help much if it's a bus, or as a mate found out many years ago, a railcar. He remembered flying through the air looking down at the passengers, before suffering a sprained ankle...
and he wasn't wearing a helmet as the rail crossing was in town.