What does 本線車道 (honsen shadō) mean? Expressway main lanes

Legal definition

Article 2(1)(iii-2) of the Road Traffic Act (道路交通法) defines 本線車道 as the roadway made up of the main lanes of a national expressway or motor-vehicle-only road. The National Police Agency's rules explain it as the part used for normal high-speed driving, excluding acceleration, deceleration and climbing lanes, roadside strips and shoulders.

The law calls the main lanes plus acceleration, deceleration and climbing lanes 本線車道等, and uses that wider term for duties after a breakdown (Art. 75-11).

Rules in the main lanes

When entering, use the acceleration lane, if any, to reach enough speed, and do not obstruct vehicles in the main lanes (Arts. 75-6, 75-7). When leaving, move in advance to the lane leading to the exit and use the deceleration lane if there is one.

Crossing, U-turns and reversing are banned in the main lanes (Art. 75-5). Even if you miss your exit, you may not back up. Stopping and parking on expressways are banned except in cases such as an unavoidable breakdown with a stop on a wide enough shoulder (Art. 75-8). If you break down on 本線車道等 or the shoulder, display a warning device (停止表示器材) and take steps to move off 本線車道等 (Art. 75-11).

The Act's intersection rules do not apply to motor vehicles traveling in the main lanes (Art. 16(3)).

Speed figures

Only the main lanes of national expressways have a legal minimum speed. Motor-vehicle-only roads have no legal minimum, and their legal maximum is 60 km/h (Enforcement Order Art. 11).

How it appears on the test, and the traps

Watch for statements that swap 'main lanes' with 'the whole expressway'.

• 'When merging into the main lanes, the merging vehicle has priority' → False (main-lane traffic has priority)
• 'The legal minimum speed on national expressway main lanes is 50 km/h' → True
• 'Ordinary roads also have a legal minimum speed' → False (none unless a sign sets one)
• 'If you miss your exit, you may back up on the shoulder' → False (reversing is banned)
• 'In a traffic jam you may drive on the shoulder' → False

Practice questions using this term

• On the main lanes of a national expressway, the statutory minimum speed for standard motor vehicles (regular cars) is 50 km/h.
• On the main lanes of an expressway, you must not stop or park even in unavoidable situations such as a breakdown.
• On the main lanes of a national expressway, the statutory maximum speed for light motor vehicles (kei cars) is 80 km/h.
• On the main lanes of a national expressway, the statutory maximum speed for large trucks is 90 km/h.
• When merging onto the main lanes of an expressway, the merging vehicle has priority, so vehicles on the main lanes must slow down and give way.
• On the main lanes of an expressway, you must not make a U-turn, reverse, or cross the median strip.

FAQ

Related guides

• Japan Expressway Rules: Max 100, Min 50 km/h, Who Can't Enter
• Japan Speed Limits: 60 km/h, 30 km/h Residential Roads, Mopeds 30
• What does 緊急自動車 (kinkyū jidōsha) mean? Emergency vehicles
• Accidents and Breakdowns in Japan: What to Do, Railroad Crossings

Sources (in Japanese)

• e-Gov法令検索「道路交通法」（第2条1項3号の2・第16条・第75条の4〜第75条の8・第75条の11）
• e-Gov法令検索「道路交通法施行令」（第11条・第27条・第27条の3）
• 警察庁「交通の方法に関する教則」（令和6年11月13日現在・全文PDF）第7章 高速道路での走行