Trailer, torrential rain and 25 metres to a braking lorry
Sunday afternoon in October. You leave Luxembourg-City on the A6 towards Belgium, dry road, with a light unbraked trailer carrying garden furniture; the train weight stays under 3.5 t. Near the Croix de Cessange a front arrives: the wipers go to maximum, and spray thrown up by the lorry ahead cuts visibility to about 80 m. The motorway is signed at 130 km/h. Your trailer's tyres are six years old and its load is slightly heavier at the back than the front. You are in the right-hand lane at 118 km/h, about 25 m behind the lorry. The lorry brakes and its brake lights are barely visible through the spray.
1. What is the correct speed and following distance in these conditions? Do the arithmetic.
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The 130 km/h sign is the limit in dry conditions. In rain the motorway limit falls to 110 km/h, and that is still a ceiling for ideal rain, not a target for this. At 118 km/h you are already over 110.
The distance is the more serious problem. The two-second rule applies in dry weather; in rain it doubles to at least four seconds, and you add more for a trailer. At 118 km/h you cover about 33 m per second, so 25 m is under one second of travel - a quarter of the minimum. Even at 90 km/h, four seconds is about 100 m. With visibility at 80 m you cannot see far enough ahead to stop from 118 km/h, and you are following a lorry whose brake lights you can barely see.
So: come off the accelerator now, let the speed fall to something where 80 m of visibility is more than your stopping distance, and rebuild the gap to well over 100 m. Realistically that means around 80 km/h or below, behind the lorry, not beside it.
2. What does the trailer add to the risk, and how do you correct for it?
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A light unbraked trailer does not brake with you: the car slows and the trailer keeps pushing, which unloads the rear axle and can start a snake. The six-year-old tyres have hardened rubber and reduced grip, so they aquaplane earlier. The rear-heavy load makes it worse: a trailer wants nose weight on the hitch, and a tail-heavy trailer is the classic recipe for a pendulum that grows until the outfit is uncontrollable.
On the road, correct by driving more slowly than you would solo, by holding the steering wheel with both hands and making no sudden inputs, and by braking early and gently, ideally with a light application first to load the trailer's hitch before braking harder. If a snake starts, do not brake hard and do not steer against it: ease off the accelerator, hold the wheel straight, and let the speed bleed away. At the next stop, move the load forward and check the trailer tyre pressures and condition.
3. The lorry brakes harder. What do you actually do in the next three seconds, and what do you switch on?
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Lift off the accelerator immediately - that is the fastest way to shed speed with a trailer without provoking a snake - and increase the gap rather than closing it. Do not dive for the left lane: with 80 m visibility there may be a vehicle alongside you that you cannot see in the spray. If you must brake, apply progressively rather than stamping on the pedal, and keep the wheel straight.
Lights: dipped headlights, which are obligatory in rain and make you visible in the spray. The rear fog light only if visibility drops below 50 m - switching it on at 80 m dazzles the driver behind you and is an offence. Hazard lights are for a genuine breakdown or a sudden queue, not for routine heavy rain.
The judgement call is to accept that you are in the wrong place: mis-matched speed and distance behind a lorry you cannot see past. Take the next exit or slow decisively until the gap is rebuilt.