Night following an unlit truck on a wet laterite road
At 22:00 you are driving a loaded 2005 Hilux south of Bissau on the EN1. The pickup carries five passengers and sacks of cashew nuts; the front tyres are at 2 mm and the rear suspension is low. A recent shower has left the asphalt wet, with laterite mud dragged across it. You are following an unlit truck at 45 m. The truck is doing about 50 km/h and has only one dim taillight. You are doing 65 km/h with dipped headlights; visibility is about 60 m. Your reaction time is about 1.2 s, and you assume braking deceleration on this wet surface is about 3.4 m/s². The road is single carriageway with a broken white centre line and no street lights. The truck brakes suddenly for a pothole. Your passenger says you can overtake because the road ahead looks clear.
1. Calculate your approximate stopping distance at 65 km/h and decide what to do about the 45 m gap.
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At 65 km/h, speed is 65 ÷ 3.6 = 18.1 m/s. Reaction distance at 1.2 s is 18.1 × 1.2 ≈ 21.7 m. Braking distance is v² ÷ (2a) = 18.1² ÷ (2 × 3.4) ≈ 48 m. Total stopping distance is about 70 m. Your gap is only 45 m, so if the truck stops suddenly you would hit it even with immediate braking. The gap is therefore too small for 65 km/h on this wet, muddy road. Reduce speed at once to about 45 km/h or less, which brings total stopping distance to roughly 38 m, and increase the gap toward 70 m. Do not wait for the truck to brake to prove the point.
2. Should you accept the passenger's suggestion and overtake? Explain.
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No. The road is single carriageway, unlit, wet and contaminated with laterite mud. Visibility is only about 60 m, and the truck has one dim taillight, so an oncoming vehicle may see you late. Your vehicle is loaded, with five passengers, low rear suspension and 2 mm front tyres, so acceleration, steering and braking are all degraded. Overtaking would also require you to close the 45 m gap first, putting you in the oncoming lane with a poor view. The passenger can see only the empty patch ahead, not the closing speed or the surface. Wait until visibility, surface, load and tyres allow a safe overtake, and until you can see a clear gap with no oncoming traffic.
3. The truck brakes suddenly for a pothole. What is your sequence, and what if you stop very close behind it?
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Brake firmly and progressively, keep the steering straight, and do not swerve into the oncoming lane or onto the muddy edge. Use the horn or flash if it helps warn the truck, but keep both hands on the wheel. ABS, if fitted, may vibrate; keep pressure on. If you stop close behind, switch on hazard lights, leave enough space to pull out if the truck rolls back, and watch for following traffic. Do not get out into the traffic lane. Once stopped, check passengers, then wait for a safe gap before moving around the truck; if the truck is disabled, pass only when you can see far enough and warn others.