If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Don't let anything get in your way, complete missions, shoot cars and just stay alive! Each specific mission brief is given at the start of every level. Dodge cars and shoot them, don't let anything get in your way. Colliding with cars and receiving fire from them will result with you losing armor. If your truck has no more armor, It's Game over.