Japan Maximum vs Minimum Speed Signs: The Underline Difference

Comparison table: maximum vs minimum speed

Both are regulatory signs (規制標識) with exactly opposite meanings. Because they look almost the same, the knowledge test (知識確認) likes questions that hinge on the underline, or on where a minimum speed actually applies.

Telling the signs apart: one line flips the meaning

Under the Order on Road Signs, Lane Lines and Road Markings (道路標識、区画線及び道路標示に関する命令), the maximum speed sign (No. 323) and the minimum speed sign (No. 324) use the same colors: blue text and symbols, red ring, white background. The only difference is the line drawn under the number on the minimum speed sign.

On electronic message boards, both may be shown as white or yellow numbers on a black background. On expressways the two signs are sometimes posted side by side, so train yourself to read the underlined one as the lower limit.

A maximum speed can also be painted on the road surface in yellow numbers (道路標示), whereas a minimum speed is set by a sign.

A statutory minimum exists only on national expressway main lanes

When no sign is posted, the only statutory minimum speed is 50 km/h on the main lanes of national expressways (Road Traffic Act Art. 75-4; Enforcement Order Art. 27-3). Memorize it as a pair with the 100 km/h maximum for standard cars: "100 and 50".

However, main-lane sections of national expressways where the two directions are not separated (two-way, head-to-head traffic) are excluded and treated like ordinary roads (Enforcement Order Art. 27-2; Rules of the Road).

Ordinary roads and motor-vehicle-only roads (自動車専用道路) have no statutory minimum. Where a minimum is needed, it is set by a sign (Road Traffic Act Art. 23).

When you may drive below the minimum

The law gives two exceptions. One is "when reducing speed under provisions of laws and regulations", that is, when another rule requires you to slow down. The other is "when unavoidable to prevent danger".

Note also that the minimum-speed duty is placed on "motor vehicles" (自動車), while the maximum speed applies to all "vehicles" (車両). A statement like "maximum and minimum speeds are just guidelines" is false: both are legal obligations.

Real questions from the knowledge test

These items from the menkyopass question set test the difference between maximum and minimum speeds.

• "Unless specified by signs or other means, ordinary roads have no minimum speed." → Answer: TRUE (the statutory 50 km/h minimum applies only to national expressway main lanes)
• "The statutory minimum speed for standard cars on the main lanes of national expressways is 50 km/h." → Answer: TRUE
• "On an expressway section where a sign sets the maximum speed, you must follow the posted speed rather than the statutory speed." → Answer: TRUE
• A common trap: reading a sign with a line under the number as a "maximum speed" → FALSE (the underlined sign is a minimum speed)

Lock it in with a mock test in your language

Two points cover this topic: the underline on the sign, and "a statutory minimum exists only on national expressway main lanes". The knowledge test has 50 questions in 30 minutes and you need 45 correct. Practice with the menkyopass mock test in your language to get used to reading signs and spotting swapped numbers.

Practice questions using this term

• On ordinary roads with a center line or marked lanes where no maximum speed is set by signs or markings, the statutory maximum speed for motor vehicles is 60 km/h.
• The statutory maximum speed for motorized bicycles (mopeds) is 30 km/h.
• On ordinary roads with a center line or marked lanes and no speed limit sign, the statutory maximum speed for large motorcycles is 30 km/h.
• On a road where signs set the maximum speed at 40 km/h, a motorized bicycle (moped) may go up to 40 km/h.
• As long as you stay within the statutory maximum speed, you may drive at that speed regardless of road and traffic conditions.
• On ordinary roads, there is no minimum speed rule unless one is set by signs or similar.
• When towing a broken-down car with a rope, the statutory maximum speed on ordinary roads is 40 km/h.
• 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 a national expressway, the statutory maximum speed for light motor vehicles (kei cars) is 80 km/h.
• For a towing vehicle (such as a tractor-trailer) used to tow a broken-down car or similar, the statutory maximum speed on national expressways is 80 km/h.

FAQ

Related guides

• Japan Statutory vs Posted Speed Limits (法定速度 vs 規制速度)
• 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
• Japanese Road Signs: Common Mistakes in the Conversion Test
• Japanese Road Signs: Regulatory vs Instruction Signs (規制・指示標識)

Sources (in Japanese)

• e-Gov法令検索「道路交通法」（第22条 最高速度・第23条 最低速度・第75条の4 高速自動車国道の最低速度）
• e-Gov法令検索「道路交通法施行令」（第11条・第27条・第27条の2・第27条の3。令和8年9月1日施行版）
• e-Gov法令検索「道路標識、区画線及び道路標示に関する命令」（別表第一「最高速度（323）」「最低速度（324）」・別表第二 色彩）
• 警察庁「交通の方法に関する教則の一部を改正する件（令和8年国家公安委員会告示第32号）」（第7章 高速道路の速度・付表 標識）
• 警察庁「生活道路の法定速度が30km/hになります（令和8年9月1日施行）」