Most semi truck drivers and race drivers use double clutch shifting. When you double clutch shift you are not going directly into the next gear, you are making a stop in neutral and you release the clutch. With double clutch shifting it makes for shifting into gears go more smoothly. Next you are pushing the clutch in again so that you can put it in the right gear, then you let off the clutch
. again. This also helps for the engine speed to match the gear speed. This is also very helpful if it is bad weather outside. You would be able to let the engine slow down so that you don't have to brake and skid.
