The Right Turn That Isn't Wide Enough
You are driving a 70-foot tractor-semitrailer with a 53-foot trailer and a 4-foot rear-axle off-track. You need to turn right from a 12-foot lane into a 24-foot-wide industrial driveway. The corner has a 20-foot curb radius, a utility pole 18 feet from the curb, and a parked car in the right lane 30 feet before the corner. The opposing lane is 12 feet wide and has oncoming traffic; a four-wheeler is following close behind. Your trailer tandem is set at 43 feet, and the trailer's rear wheels track inside the tractor's path. The driveway is clear, but its gate is only 40 feet from the road, so you cannot pull far in before turning.
1. Plan the turn. Where should you position the combination, when should you begin the turn, and how should you use the mirrors?
Read the worked answer
The geometry is the problem: a 53-foot trailer with 4 feet of off-track means the trailer rear wheels will cut well inside the tractor's path, and the 20-foot curb radius is tight for a 70-foot combination. Staying hard in the 12-foot right lane and turning at the corner will likely put the trailer tires over the curb or into the utility pole. A left swing can help, but the opposing lane is only 12 feet wide and has traffic, so the swing must not become an unsignaled lane change into an occupied lane. The practical plan is to stop before the corner, let the close-following car pass or back off, signal early, and position as far left as is legal and clear while keeping the tractor in the right lane or at its edge. Begin the turn late, after the tractor's rear axle has passed the corner, so the trailer follows a wider arc. Watch both mirrors continuously: the right mirror for the trailer tires and pole, the left mirror for the trailer tail swing and the car behind. If the trailer cannot clear the curb without crossing into oncoming traffic, do not commit; use a spotter or choose another route.
2. As you swing left, the following car moves into the right side of your trailer. What do you do?
Read the worked answer
Stop the turn and hold the combination still. The car is now in the space the trailer needs, and continuing the swing will either squeeze the car against the curb or force the trailer into the opposing lane. Do not wave the driver through, because the car may move into a blind spot or into the path of the trailer's rear wheels. Keep the brakes applied, check both mirrors, and if you cannot see the car clearly, do not move. A four-wheeler that has moved up the right side is in the most dangerous position for a right turn; the trailer's off-track can crush it against the curb even at low speed. Wait for the car to back up or for a safe gap, then re-establish your position. If the car will not move and traffic builds, a spotter can help, but the driver should not complete the turn on the assumption that the car will get out of the way. The correct judgment is to give up the turn and reposition rather than force it.
3. Why is swinging wide into the opposite lane not automatically safe, even if it makes the trailer clear the curb?
Read the worked answer
Swinging wide trades one hazard for another. The opposing lane is 12 feet wide and occupied; crossing the centerline puts the tractor or trailer into oncoming traffic, and the trailer's rear tail swing can strike a vehicle that is legally waiting at the intersection. A wide swing also changes the angle so that the trailer may cut back across the curb later in the turn, especially with a 20-foot curb radius and a gate only 40 feet from the road. The driver may be looking at the curb and miss the oncoming car or the utility pole on the inside. The safe principle is to use only the space that is legal, clear, and visible, and to stop if those conditions are not met. If the turn cannot be made without entering an occupied lane or hitting the curb, the driver should wait, use a spotter, or take a different route. Making the turn is not worth a sideswipe or a right-turn squeeze crash.