The surface under your tyres decides how much grip you have, and it changes more often than you'd think. Whenever it changes, adjust — different surfaces handle very differently, especially when wet.
Asphalt
Smooth black asphalt gives good grip when dry, but its skid resistance drops in the wet — slow down and take extra care when it's raining.


Chip-seal
Where chip-seal has worn smooth, grip is reduced, so watch for those polished patches. On newly laid chip-seal, slow down — loose chips can increase your risk of skidding.
Unsealed and gravel roads
Gravel (loose metal) roads have very low skid resistance, and loose stones can chip or break a windscreen, so take extra care and adjust your speed. Following another vehicle on a dry gravel road, increase your following distance to stay back from the dust cloud, which cuts your visibility.
