ABS warning light, wet cobbles and a sudden stop
You ride a motorcycle with ABS on wet cobblestones in an Austrian town at 45 km/h. Your ABS warning light came on when you started the bike and has stayed on. The front tyre has 2.5 mm of tread in the centre and the rear has 3 mm; both are correctly inflated. A pedestrian steps off the pavement 20 metres ahead without looking, and you must brake hard. The road surface is uneven, with a tram rail crossing your path diagonally about 8 metres ahead. Your front brake lever feels normal and the rear brake pedal has normal travel.
1. What does the illuminated ABS warning light mean for your braking in this situation, and how should you use the brakes?
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A warning light that stays on after start-up means the ABS is not functioning, so you must treat the bike as having conventional brakes. On wet cobblestones, with a tram rail ahead, locking a wheel is a real risk. Apply both brakes progressively and firmly rather than snatching the front lever: build pressure smoothly so the front tyre has time to load up, and use the rear brake to help stabilise the bike. Do not rely on ABS to prevent a lock-up, and do not pump the lever in a panic - controlled, increasing pressure gives you the best chance of stopping without the front washing out. Keep the bike upright and avoid braking hard while crossing the diagonal rail, where grip is lowest. The 20 metres available at 45 km/h is short on this surface, so your speed should already have been lower given the wet cobbles and the failed ABS.
2. How do the tyre tread depths affect your decision, and what would you do after this incident?
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The front tyre at 2.5 mm is close to the legal minimum and, more importantly, has limited ability to clear water on cobbles, so aquaplaning and loss of grip are more likely. The rear at 3 mm is little better. On a wet, uneven surface these depths mean you should ride well below the speed the dry road would allow, increase your following distance, and brake earlier and more gently. After the incident, get the ABS fault diagnosed before riding further - a motorcycle with a known brake-system fault should not be used in wet conditions. Replace both tyres, since tread near the minimum on wet cobbles is a safety issue even if it is technically legal. Until then, avoid cobbles and tram rails where possible and reduce speed accordingly.