Black Ice in Iiyama: Where and When to Expect It

A road that looks only wet and black may be covered by a thin layer of ice. Expect possible freezing after rain or snowmelt, especially overnight and around dawn.

Checked October 25, 2026. Confirm current weather, roads and provider conditions before travel.

APPEARANCE: Looks like wet asphalt
TIME: Night and early morning
PLACES: Bridges, shade and tunnel entrances

Rain or snowmelt can refreeze

JAF notes that water from daytime snowmelt or rain can freeze as temperatures fall at night or toward dawn. A dashboard temperature display cannot confirm the road surface is safe.

Slow down before the high-risk place

Bridges and elevated roads cool quickly. Shade, tunnel entrances and approaches to junctions also deserve caution. Reduce speed and increase distance before reaching them, rather than reacting with a sudden input after the car slides.

Winter tyres and 4WD have limits

Avoid sudden braking, steering and acceleration. Four-wheel drive may help movement but does not guarantee braking or cornering on ice. Switch to public transport when the conditions exceed your experience.

FAQ

Questions before driving

Practical answers for planning your route and rental.

Can I see black ice?

It may look like ordinary wet asphalt, so drive on the assumption that it may be frozen when conditions are suitable.

Where is it most likely?

Bridges, elevated roads, shade, tunnel entrances and cold roads at night or dawn.

Does 4WD prevent sliding?

No. It does not guarantee shorter braking distance or safe cornering.

Sources

JAF snow and black-ice guidance / Nagano winter-road cautions