Wet Leaves and Frost Arrive on a Schedule

Most road hazards appear without warning. Seasonal ones do not, and that predictability is the most useful thing about them.

Leaves are slippery for a specific reason

Fallen leaves crushed by traffic release compounds that form a thin slick layer bonded to the road. Wet leaves are not merely a loose surface.

That layer persists after the leaves themselves are swept away, which is why a road can remain slippery once it looks clear.

The effect is strongest on the first wet days after a dry spell of leaf fall, when accumulated material is mobilised at once.

Leaves collect where riders ride

Wind and passing traffic move debris toward the edges of the carriageway. The gutter and the cycle lane are where it ends up.

They also gather at the base of descents and in the lee of walls and parked cars, which are exactly the places where a rider is likely to be braking or turning.

Riding slightly further out through leaf-fall weeks avoids the worst of it. The cost is a position further into the traffic stream, which is a trade to make deliberately.

Frost forms unevenly and predictably

Ice forms first where surfaces lose heat fastest, which means bridges and elevated sections chilled from above and below. They freeze well before adjacent road.

Shaded stretches under trees or between buildings retain ice long after the rest of a route has thawed. The pattern repeats in the same places each year.

Painted markings, metal covers and smooth concrete all reach lower surface temperatures than asphalt and ice earlier. These are the specific points to note on a familiar route.

Black ice is a visibility problem more than a grip problem

A thin transparent layer over dark asphalt looks like wet road. The surface appears slightly darker and glossier, which is a weak cue at speed.

The reliable indicator is temperature combined with recent conditions. Clear still nights following a wet day produce the widest coverage.

Where ice is suspected, avoiding steering and braking inputs while crossing it is the technique. Grip is often sufficient to travel straight and insufficient to turn.

Spring and summer bring their own surface changes

Grit spread through winter remains on the road well into spring, concentrating on corners and at the edges where it was pushed by traffic.

Hot weather softens tar and can bring oil and rubber to the surface, which then becomes slippery in the first rain after a dry spell.

The common thread is that each season concentrates a specific hazard in a specific place. A rider who knows which one is current is reacting less and anticipating more.