Deer at night on an unlit cantonal road
It is 22:40 in November. You ride a 600 cc motorcycle on a cantonal road in open countryside, in an 80 km/h section, at an indicated 75 km/h. The asphalt is wet, and the right-hand bend ahead is covered with wet leaves in your lane. There is no street lighting. An oncoming car about 150 m away still has its main beam on, so you are running on dipped beam. Your dipped beam lights up roughly 45-50 m of road, and your tyres and brakes are in good condition. At the outside of the bend, on the right verge about 55 m ahead, you catch two points of eyeshine at the height of the grass shoulder, and the shape does not move. A steel guardrail runs along the left edge of the road; on the right there is only grass verge and a drainage ditch. The oncoming car is now 120 m away. You are alone on the bike and the road behind you is empty.
1. At 75 km/h, can you stop for a hazard 55 m ahead? Show the arithmetic and state what you do now.
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No - the hazard at 55 m is inside your stopping distance.
- 75 km/h = 20.8 m/s.
- Reaction and brake application: realistically about 1 s before the brakes bite, so about 21 m travelled.
- Braking at a realistic 6 m/s² on wet asphalt: 20.8² / (2 × 6) ≈ 36 m. On wet leaves expect about 5 m/s², so roughly 43 m.
- Total: about 57-64 m against a hazard at 55 m, before allowing for the fact that your dipped beam shows only 45-50 m and that you are being dazzled.
A full stop before the deer is therefore not available at this speed. The decision has to be made now: reduce speed immediately to about 50 km/h (13.9 m/s, which gives roughly 14 m reaction plus 16-19 m braking, about 30-33 m), cover the brakes with two fingers, and keep the bike straight and upright over the leaf patch. Slowing by 25 km/h cuts your kinetic energy by more than half and buys you the option of stopping.
2. The deer stays frozen. Evaluate a swerve to the left and a swerve to the right, and say what you commit to.
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Brake straight - do not swerve left, and do not commit to a swerve right.
- Left is closed. The oncoming car is 120 m away and closing at about 150 km/h combined, so you have roughly three seconds, and you would be riding into main-beam glare. A head-on at that speed is fatal.
- Right is unknown. Grass verge, a ditch and possibly a fence, plus wet leaves: you would be braking on a surface with a fraction of the grip and aiming at the animal rather than past it.
- Straight-line braking always works. With ABS you can brake hard and still steer, so brake progressively to the limit, keep the bike upright over the leaves, and look for the gap past the animal rather than at it. Stay ready to ease off if the front starts to slide.
- If the deer moves off, release and continue. If it does not, a decelerated impact with the bike upright is survivable, whereas a high-speed deflection into the guardrail or the oncoming car is not.
- Decide once and commit. Hesitating between braking and swerving is what turns a near miss into a crash.
3. What should you have done differently on this road, before the bend?
Read the worked answer
Four things.
- Speed. At night in deer country ride so that you can stop within the distance your dipped beam lights. About 45-50 m of light means no more than roughly 60 km/h even with a 1 s reaction and good grip, and less on wet leaves. The 80 limit is a maximum, not a target.
- Light. With an oncoming car 150 m away you were right to dip, but you can still use main beam until the glare genuinely becomes a problem; dipping 150 m early threw away half your warning distance. Look at the road edge and the verge rather than into the oncoming lights.
- Line and scanning. Ride where you can see furthest round the right-hander without crossing the centre line, and scan the verge for eyeshine instead of staring at the road 20 m ahead. Deer travel in groups: after one, expect another.
- Equipment. Clean visor, no dark or tinted visor at night, and a headlight correctly adjusted for load.