U-turns are never a safe option and are particularly dangerous at night or in areas of limited visibility.
Studies have shown that making a U-turn from a stop takes the average truck at least 40 seconds to complete. During that time, the trailer is blocking the travel lanes and presents a hazard to all other traffic. (60 mph traffic will travel approximately 3/4 of a mile while you are completing this maneuver).
At night, the brightness of the truck's headlights will mask the marker lights on the trailer. The reflective striping on the side of the trailer is invisible until the trailer is close to being at a 90 degree angle across the road. Combine these phenomena with the fact that a car driver sits low enough to see under the trailer and focuses on lights that are farther away and you have created an invisible barrier for approaching traffic.
Trailer run-unders are almost always a catastrophic event.
Avoid U-turns across highways. Rather, find a safe location to turn around in and then make a normal pull-out and turn. Even then, keep in mind that the average pull-out and left turn takes as much as 17-20 seconds. Never make such a turn if traffic is close enough that it will be required to adjust to your presence.
U-Turn collisions are PREVENTABLE.