Right Turn With a Wall and a Van
A tractor-drawn 75-foot aerial responds to a two-story strip mall with smoke from the rear. The access is a 20-foot-wide driveway that intersects the street at 90 degrees, with a 4-foot-high masonry wall on the right and a parked delivery van on the left. The street is a two-lane road with a 35 mph speed limit and moderate traffic. The driver must make a right turn into the driveway, but the trailer's rear wheels will off-track toward the wall. The tiller operator can steer the trailer wheels. The driveway slopes up 3 percent toward the building, and the building sprinkler connection is 30 feet inside. The driver is worried about blocking traffic and wants to take the turn at 10 mph.
1. Explain the off-tracking in this right turn and how the tiller operator should steer the trailer wheels.
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In a right turn, the trailer's rear wheels track inside the tractor's path, toward the masonry wall. The sharper the turn and the longer the combination, the more the rear of the trailer cuts the corner. The tiller operator must steer the trailer wheels to widen the rear path, but the input must be gradual. Steering the trailer wheels hard in the wrong direction will cut the corner further or swing the trailer nose toward the van.
The driver should start the turn wide, using the available street width while keeping clear of traffic, and the tiller operator should feed steering in small corrections. The tiller operator should watch the wall and the van and call stop before the trailer tires reach either obstacle. At 10 mph, the corrections come too fast for a 75-foot combination and a 20-foot driveway. The turn should be taken at walking pace or slower, with a spotter if the mirrors do not show both sides. If the trailer's rear wheels cannot clear the wall, the driver should stop and reposition rather than force the turn.
2. Traffic is moderate. Should the driver take the turn immediately or use another approach? Give your reasoning.
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The decision is not traffic alone; it is whether the combination can clear the wall and the van without contact. If the turn geometry requires the trailer to cross the centerline or block both lanes, the driver should stop, set the parking brake, use warning lights, and request a spotter or traffic control. If traffic prevents a safe setup, the better option may be to continue past the driveway and approach from the opposite direction, making a left turn into the driveway. A left turn may put the trailer's off-tracking toward the open side instead of the wall.
The presence of smoke does not justify forcing a turn that damages the apparatus or strikes a vehicle. Before committing, check overhead wires, the 3 percent slope, and the sprinkler connection location. The driver should also consider whether the aerial can be set from the street or another access point. Blocking traffic briefly under control is safer than a collision or a damaged trailer.
3. How does the 3 percent up-slope affect spotting and stabilization once the apparatus is in the driveway?
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The slope changes the load on the outriggers and the angle of the turntable. The apparatus should be positioned so the turntable is as level as possible within the manufacturer's limits. In some cases, using the slope to place the turntable nose-down or nose-up may keep the aerial's operating envelope legal, but the level indicator and the manufacturer's slope limit govern.
Chock the wheels on the downhill side and in both directions. Use cribbing under the outrigger pads to spread the load and compensate for the slope. Do not rely on the parking brake alone. Check the bubble level before raising the aerial and recheck it after the outriggers are loaded. If the slope exceeds the manufacturer's limit for aerial operation, reposition the apparatus or use another access point. Keep the sprinkler connection clear and confirm that the outrigger pads are on firm ground, not on the edge of the driveway.