Trailer Swing on Wet Route 17
It is a Friday afternoon in Paramus. Light rain has just started after two dry weeks, so the asphalt on Route 17 south is slick with oil and water. You are pulling an empty 53-foot van with a 3-axle tractor, running about 50 mph in the center lane. The curve ahead is posted 40 mph. A car in front of you brakes suddenly. You apply the foot brake firmly. The trailer wheels lock, the trailer swings left toward the left lane, and the tractor-trailer angle begins to close. Your steering wheel is still pointed mostly straight. A box truck is alongside you in the left lane, and the right shoulder is narrow with a guardrail. You have anti-lock brakes on the tractor and trailer, but the trailer ABS warning lamp was on when you did your walk-around and you noted it.
1. Identify what is happening and your first control action. Why would braking harder or holding the brake make it worse?
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The trailer wheels have locked and the trailer is swinging into a jackknife. The first action is to release the brake pedal so the trailer wheels can roll again; locked wheels have less directional stability and the trailer will keep rotating. As the trailer comes back, steer smoothly in the direction the trailer is moving, but do not overcorrect into the box truck. If the trailer swings left, a controlled left steering input helps the tractor follow and close the angle; a violent correction can start a counter-swing. Braking harder keeps the trailer wheels locked, increases the angle, and can put the combination across both lanes.
2. What should you do about the box truck and narrow shoulder as you recover? Why is an empty trailer more likely to do this?
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Do not steer blindly into the left lane where the box truck is. Release the brake, straighten the combination as much as the space allows, and use only gentle braking once the trailer is rolling and aligned. If the box truck is alongside, hold your lane and slow gradually rather than swerving; a rollover or sideswipe is worse than a longer stopping distance. The shoulder is too narrow for a sudden exit at speed, so use it only after the combination is under control and slowed. An empty trailer is light and bouncy, with less tire loading and less traction; its wheels lock more easily on wet pavement, and the trailer ABS lamp being on means the trailer ABS may not be helping.
3. What would you do differently on the next trip, and what does the ABS warning lamp mean for your decision to drive?
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Slow before the curve, especially on the first rain after a dry spell when oil is floating on the surface. Use gentle, progressive braking and a lower speed for an empty trailer; avoid engine-brake or retarder use on a wet, empty combination because drive-wheel lock can start a skid. The trailer ABS lamp staying on means the trailer ABS is not functioning normally. That does not necessarily mean the trailer has no brakes, but it does mean you cannot count on ABS to prevent wheel lock. It should be repaired before dispatch; if it comes on during the trip, treat the trailer as more skid-prone and adjust speed and following distance.