Rainbows (oil sheen on wet roads)

On a wet road, spilled oil, diesel or fuel spreads into thin films that show up as rainbow-coloured patches. For a motorcyclist they are a clear warning: grip on these spots can be a fraction of normal wet grip.

They are most common at junctions, roundabouts, petrol stations, bus stops and the middle of the lane where vehicles drip fluids. The first rain after a dry spell is especially slippery because oil and dust are lifted from the surface.

When you see a sheen, avoid braking, accelerating hard or leaning over on it. Ride through upright and smoothly, or choose a cleaner line if you can do so safely.