Truck Speed Limit, No-Passing Pennant, and a Wet Downgrade
You are driving a 2018 half-ton pickup (gross vehicle weight rating 7,000 lb) pulling a 3,500-lb utility trailer on a two-lane Montana highway. The trailer has no brakes. It is raining steadily. Ahead, on a long downgrade, you see: a white rectangular sign reading SPEED LIMIT 70; below it, a white sign reading TRUCK SPEED LIMIT 60 with a plaque reading VEHICLES OVER 26,000 LBS GVWR; a yellow NO PASSING ZONE pennant; and a yellow sign reading TRUCKS USE LOW GEAR. Your combined gross weight is about 10,500 lb. A tractor pulling a hay baler is moving at 25 mph ahead. Your passenger asks whether you can use the oncoming lane to pass because the tractor is slow, and whether the 60-mph truck limit applies to your rig. You have about 2 miles of downgrade before a curve.
1. Which posted speed limit applies to your pickup-and-trailer combination, and how should the plaque under the TRUCK SPEED LIMIT sign affect your answer?
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The general SPEED LIMIT 70 sign applies to your combination because the truck limit is qualified by its plaque: VEHICLES OVER 26,000 LBS GVWR. Your pickup GVWR is 7,000 lb and the trailer is 3,500 lb, so the combination is about 10,500 lb, well below 26,000 lb. The 60-mph truck sign therefore does not lower your posted limit by its own terms. That does not mean 70 mph is a target. The posted limit is a maximum for favorable conditions; steady rain, a downgrade, and a trailer without brakes are all reasons to travel slower under the basic speed law. Choose a speed that lets you stop within the distance you can see and control the trailer without brake fade.
2. Can you legally pass the 25-mph tractor using the oncoming lane? Explain the role of the NO PASSING ZONE pennant and the wet downgrade.
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No. The yellow NO PASSING ZONE pennant marks the beginning of a no-passing zone for your direction. It is not merely a suggestion, and the tractor's low speed does not create an exception. You must stay behind the tractor until you reach a location where passing is both legal and safe: typically a broken yellow line on your side, adequate sight distance, and no sign or pavement marking prohibiting the maneuver. Here the wet surface, the downgrade, and the approaching curve all reduce your margin for error. Passing would also require accelerating on a slick downgrade while judging a closing curve, so the legal prohibition and the safety risk point the same way: wait.
3. What should you do about the wet downgrade, and why does the TRUCKS USE LOW GEAR sign matter even though you are not driving a heavy truck?
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The sign warns that the grade is steep enough to require engine braking rather than continuous service-brake use. Even a light trailer can push a pickup on a wet downgrade, and the trailer has no brakes of its own. Select a lower gear before the grade steepens, let engine braking control speed, and use the service brakes in shorter applications rather than riding them. Keep extra following distance because stopping distances grow on wet pavement. If a line forms behind you, use a legal turnout or pullout when available rather than speeding up beyond a safe speed. The goal is to avoid brake fade and loss of traction, not to match the posted maximum.