Night rain, lorry spray and an impatient overtaker
22:10, steady rain, full darkness. You are riding a 650 cc adventure bike on a two-lane regional road outside a town where the limit is 80 km/h, at an indicated 75 km/h. You sit about 30 m behind a lorry that throws up heavy spray; its tail lights smear into two red blobs and are the only thing you can see clearly. Your visor is beaded and your gloves are soaked. The road ahead curves right and the lorry's trailer tracking tells you the bend tightens. A construction-site entrance a kilometre back means there may be washed gravel near the apex. A car has been behind you for 5 km with its lights filling your mirrors, and it has now pulled out to overtake on a stretch where you cannot see far ahead. Tyres are at the solo pressures from the manual.
1. Is 30 m an acceptable gap at 75 km/h in these conditions? Show the arithmetic you would use.
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No. Convert speed first: 75 km/h is about 20.8 m/s, so 30 m is only about 1.4 seconds of following time. The two-second rule is a dry-daytime minimum, and 75 km/h would already require roughly 42 m.
Now add stopping distance. Reaction at one second covers about 21 m. Wet braking on a loaded touring tyre at perhaps 0.45 g needs about 49 m more. That is roughly 70 m to stop from 75 km/h - and the lorry can stop in a shorter distance than you can, so a gap shorter than your own stopping distance means you will hit it before you can halt.
Rain, spray, beaded visor and darkness all push you towards the upper end: three to four seconds, so roughly 62–85 m. Drop back to at least that, using the lorry's tail lights as a distant reference rather than a target.
2. How do you plan the tightening right-hand bend, knowing there may be gravel near the apex?
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Everything happens before the bend, not in it. Ease off the throttle early so the speed is set while you are still upright and the road is visible; you cannot brake hard mid-corner on a wet road with possible gravel.
Choose a wider entry so you can see further round the tightening curve, and delay the turn-in slightly. Keep the bike more upright than you would in the dry, avoiding a line that puts you on the apex where the gravel will be. If you do meet loose gravel, hold a steady throttle, keep the bars relaxed, and avoid a fistful of front brake - a locked front wheel on gravel puts you down almost instantly.
The lorry gives you information: watch how its trailer swings and whether its wheels throw up debris, which tells you where the loose material is.
3. The car behind is now committed to overtaking. What do you do, and what do you expect it to do next?
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Hold your speed and your line. Do not accelerate to 'help' it past - that shortens the space it needs and pushes you towards the lorry - and do not brake or swerve to the right into the gutter.
Expect it to cut back in early: with a bend ahead it cannot see far, and if something appears it will dive for the gap between you and the lorry. That gap is where you are, so create room. Roll off the throttle gently and let the distance to the lorry grow, so a car cutting in front of you does not force you to brake hard on a wet road.
If it passes and slots in close, do not react with a flash or a gesture; simply ease off further and rebuild the three-to-four-second gap. Being right matters less than being seen and having space.