Driving in Japan in winter: studless tires, chain regulations, black ice, and what #9910 is (and isn't) for

Renting a car for a ski trip in Japan? Snow and ice change everything, and some Japanese rules surprise visitors. This guide uses Japan's transport ministry, regional road agencies and police, plus tests by the Japan Automobile Federation (JAF), with our translations where the source is in Japanese.

Tires

• Check before you drive off. JNTO advises: "Confirm with the rental car company in advance that the tires are not regular tires but the studless ones."
• All four wheels. Japan's regional road office in Mie says studless tires should be fitted on all wheels, and about three years from first use is a rough limit.
• Snow-tire wear marks. On winter tires from Japanese makers, a "platform" mark appears in the grooves when the tread is worn to 50% of new; the transport ministry calls this the guide to the wear limit.
• All-season tires are meant for light snow, according to the transport ministry. For harsh snow and ice, it asks for winter tires with the snowflake mark on all wheels.
• Prefectural rules require anti-skid measures on snowy roads (except Okinawa), and fines can apply (7,000 yen for large vehicles, 6,000 yen for regular cars).

Chain regulations

In exceptional snowfall, Japan may impose chain regulations on designated sections. The transport ministry is clear: vehicles with studless tires but no chains cannot pass. Four-wheel-drive vehicles are not exempt, and spray-on traction products don't count. Chains go on the drive wheels, and they are checked before the regulated section. Ask your rental company for chains and practice fitting them once (our suggestion).

Black ice and bridges

Japan's Civil Engineering Research Institute for Cold Region describes black ice as a film of ice less than 1 mm thick on the pavement. Bridges are cooled from above and below, so they can be icy even when other roads look dry. Roads that are merely wet in the daytime can freeze at night.

What JAF's tests showed

• On packed snow at 40 km/h, regular tires needed about 1.7 times the stopping distance of studless tires; on ice, about 1.8 times that of chains.
• Regular tires couldn't climb even a 12% snowy slope. On an icy slope, studless tires with chains made it up.

When you park

The Mie road office advises not setting the parking brake in freezing conditions, since the cable can freeze; use wheel chocks instead.

If something goes wrong

• Emergencies: 110 (police) or 119 (fire and ambulance).
• Japan's #9910 line is for reporting road hazards such as potholes or fallen objects, not for roadside assistance. For breakdowns, contact your rental company or JAF's roadside assistance.
• If you get stuck in heavy snow, see "Stuck in your car in a snowstorm." Clear snow from the exhaust pipe to prevent carbon monoxide poisoning.

A Japanese version is available: "冬道の運転" (in Japanese).