its quite easy to explain in Pakistani terms.
when you are on a mini bus/wagon and its going 30 km/h and you forgot to get off at your stop because
1 - you were busy staring at the ladies at front
2 - your "lady" got off at the bus stop and the bus started to move again.
now when you get off from the bus you actually have to run forwards "alongside the bus" because your ground speed is 30 km/h and your direction is following the path of the bus even if you are standing still on the bus - you run forwards and let go of the handle and then proceed to stop in order not to fall over.
If you are stupid you jump straight out and dont run - you will fall over and tumble down the road and be promptly run over by another vehicle - (dont worry - edhi etc will scrape off your body from the road).
urdu mein - chaltee buss se utarr te waqt agar aap na bhage to aap gir jaayne
in case of driver of car in this case - in the event of a crash the driver of the car will be thrown towards the point of impact as they are actually travelling (at same ground speed and direction of car) - the car suddenly stops but your body has weight and volume, it will want to keep on moving (newton chachoo ka qanoon) - the seat belt is supposed to stop you from moving and the airbag is supposed to "catch" you as you are not a brick but have articulated joints.