Crosswind Sway With Empty Pups on the Interstate
You are pulling two empty 28-foot pups on I-71 near Mansfield at 65 mph in the right lane. A crosswind gust hits as a tractor-trailer passes. The rear pup begins to sway left and right; the steering feels light, and you have cruise control set. The pavement is damp. Your right mirror shows the rear pup's tires crossing the lane line. A guardrail is 20 feet to the right, and traffic is close behind. The first pup is empty, the second has 1,500 lb of pallets. The wind is reported at 25 mph gusting to 40 mph. You are 8 miles from the next exit and have been driving for 5 hours.
1. What is the first corrective action, and what must you avoid?
Read the worked answer
Disengage cruise control immediately and ease off the accelerator. Keep the steering wheel firmly in both hands and steer straight; do not saw the wheel or countersteer sharply against each sway. Avoid hard braking, because locking or aggressively applying brakes during a sway event can transfer weight and trigger a jackknife or loss of control, especially with empty trailers and damp pavement. If you must slow, use a light, steady brake application after the trailer begins to straighten. The goal is to let the combination settle rather than chase the rear pup with steering. Empty pups are light and more affected by wind and passing trucks, so reducing speed is the main corrective tool once control is regained.
2. The rear pup's tires are crossing the lane line and the guardrail is close. What do you do if the sway does not settle?
Read the worked answer
Continue easing off the accelerator and hold a straight steering line. If the sway is not settling, use a gentle, progressive brake application rather than a hard stab, and look for a safe place to stop. Do not jerk the wheel toward the shoulder; that can start a sharper sway or a skid. If the rear pup is already over the line, avoid overcorrecting back into the lane. Once speed is reduced and the trailer is stable, pull onto the shoulder or take the next exit, even if it is 8 miles away, and inspect the hitch, tires, and load. If the combination is uncontrollable, a controlled gradual slowdown is safer than a sudden stop in traffic.
3. What factors caused this event, and how would you prevent it on the rest of the trip?
Read the worked answer
The causes are low trailer weight, a crosswind gust, the air disturbance from the passing tractor-trailer, damp pavement, and speed too high for the conditions. Empty pups have little resistance to sideways force. Prevention starts before the gust: reduce speed in high winds, do not use cruise control in gusty or wet conditions, increase following distance, and avoid passing or being passed at high speed when possible. Keep the steering smooth and anticipate wind blasts at bridge openings and when large vehicles pass. If the load can be shifted or ballasted legally, that can improve stability, but the immediate fix is lower speed and full attention. After the event, stop and check tires, air lines, and the dolly connection before continuing.