Trailer Swing on an Icy Bridge Deck
You are driving a 53-foot empty van at 40 mph on an elevated bridge with a 200-foot shaded deck. The temperature is 28°F, and freezing rain is falling. As you cross the expansion joint, the drive tires spin up and the trailer begins to swing left toward the jersey barrier. You have 150 feet to the end of the bridge. A box truck is 200 feet ahead in the right lane. You are in the left lane. The steering axle is still on the dry approach, but the drive and trailer axles are on ice. You have released the accelerator, but the trailer continues to swing. Your foot is near the brake pedal.
1. What type of skid is developing, and what is the correct immediate action?
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This is a trailer swing that can become a jackknife. The drive tires have lost traction and the trailer is pushing the tractor, so the angle between tractor and trailer is increasing. The immediate action is to release the brakes if they are applied, keep the steering smooth, and steer in the direction the trailer is moving, which is left, to bring the tractor back into line with the trailer. Do not stab the brakes or accelerate. Because the steering axle is still on dry pavement, a smooth steering correction has a better chance of working than a hard brake application. Once the trailer starts to come back, straighten the wheel gradually; overcorrecting can start a swing in the other direction.
2. Why is hard braking or countersteering away from the trailer wrong?
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Hard braking on ice will lock the drive tires or trailer tires and remove the little steering control you have. If the trailer wheels lock, the trailer can swing farther out; if the drive wheels lock, the tractor can spin. Countersteering away from the trailer increases the angle between tractor and trailer and can turn a trailer swing into a full jackknife. The trailer is already moving left; steering right makes the tractor point away from the trailer instead of following it. You want the tractor to align with the trailer, not to fight it. Release the brakes, steer smoothly toward the trailer's direction, and avoid any sudden throttle or brake input until the combination is straight and back on dry pavement.
3. What should you do once the combination is straight and off the bridge?
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Once straight and off the ice, slow gradually with light braking and find a safe place to stop. Check the tires, the trailer coupling, and the air lines, and inspect for damage from the barrier or the expansion joint. Then decide whether to continue. The freezing rain is still falling, so the next bridge or shaded patch may be just as slick. Reduce speed, increase following distance, and avoid cruise control. If conditions are worsening, stop for the night rather than pushing through. The empty trailer is light, which makes it more likely to swing and less likely to push the drive tires down onto the ice. That is a reason for more caution, not less.