The semi truck’s tractor and trailer have a combined length of about 70 feet. A typical highway lane width is about 12 feet. As one might expect, making a u-turn with a semi truck on a two lane highway isn’t easy. It’s also dangerous becauseĀ a semi truck takes a long time to execute the maneuver and blocks both lanes. Additional reasons semi truck u-turns are dangerous include: The Semi Truck Has Large Blind Spots Unlike a car that permits a 360 degree view when the driver turns her head, the.