Lane Change, Low Bridge, and Tight Turn With Triples
You are pulling 28-foot triple pups, 80,000 lb gross, eastbound on a 4-lane divided highway with a 65-mph limit and a 15-mph crosswind from the right. You need to move from the right lane to the left lane to avoid a disabled truck on the shoulder. Traffic is heavy; the gap behind you is 300 feet at 65 mph, and the gap ahead is 150 feet. Your combination is 82 feet long. The bridge you must pass under is posted 13 feet 9 inches, but the pavement has been resurfaced 4 inches since the sign was installed. Your trailer height is 13 feet 6 inches. Your route also requires a right turn at a tight corner with a 20-foot curb radius. What do you do?
1. Is the 300-foot rear gap and 150-foot front gap enough for this lane change at 65 mph? Show the reasoning.
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At 65 mph, the vehicle travels about 95 feet per second. A 300-foot gap behind is about 3.2 seconds, and a 150-foot gap ahead is about 1.6 seconds. For an 82-foot triple, that is not enough, especially with a 15-mph crosswind and the rearward amplification of the last trailer. I would not change lanes into that space. I would slow down, signal early, wait for a larger gap, and make one smooth lane change. The rear trailer can swing wider than the tractor, so I need more room than a single trailer would require.
2. What about the bridge clearance? Can you pass under it?
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I would not pass under the bridge. The sign says 13 feet 9 inches, but the 4-inch resurfacing reduces the actual clearance to about 13 feet 5 inches. The trailer is 13 feet 6 inches tall, so it is about 1 inch too tall. I would treat the posted clearance as a warning, not a guarantee, and route around or stop and verify the actual clearance with the proper authority. Hitting a bridge is a serious incident and can peel the trailer roof.
3. How do you handle the right turn with a 20-foot curb radius?
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For the 20-foot curb radius, I would swing wide before the turn, use both mirrors, and watch the rear trailer's tires and the curb. The rear trailer off-tracks toward the inside of the turn, so I need enough room in the left lane or approach lane to keep the trailer tires off the curb and away from poles. I would not turn if the space is too tight; I would stop and reassess or take another route. A spotter can help, but the driver must still confirm the trailer path.