You hired as a forest worker and truck driver. Your new boss seems to be an idiot, because he wants you to drive the freight unsecured to the destination! Since you don't want to loose your job you consent.
Each level you have to deliver a certain amount of freight to the destination. Sometimes it's loose wood sometimes it's crates. At the beginning wait til the freight is loaded completly onto your forest truck. Then drive when the light goes green using the ARROW KEYS. UP is for gas, DOWN for brake. LEFT and RIGHT are for balance. Don't loose too much of the freight or your job isn't done. In addition you have to deliver the freight in time (watch the time meter top left)! And don't ram into the stacked cargo at the destination, you will loose points this way. If you need to retry a level, click on the small reload button at bottom left.