Speed limits in Japan
Statutory speed limit in Japan defaults to  for divided national expressways and  for any other roads, unless otherwise posted. Urban two-way streets are usually zoned at  or less.

The highest speed limit in Japan is  on sections of Shin-Tōmei Expressway (E1A) and Tōhoku Expressway (E4), and expressways in the Kantō Plain leading to Tokyo.

Summary
Statutory maximum speed limits of  applies on divided national expressways and  on other roads. There are no separate urban or rural statutory limits. Urban and rural limits are set by zoning rather than statute. Statutory speed limits for heavy trucks with GVWR over , trailers and three-wheelers are restricted to  on divided national expressways (although raising of speed limit for trucks over 8 t has been considered to allow faster goods deliveries).

Implementation of speed limits in Japan can be summarized as:
 regulatory speed limits of  on residential streets and  are common for urban two-lane roads.
 regulatory speed limit of  or  is common in rural areas due to rugged mountainous terrain.
 regulatory speed limit cannot be set higher than  for any streets with an at-grade intersection, or where pedestrians or cyclists are permitted.
 undivided expressways have a limit of .
 variable speed limits are in effect on most national expressways.
 emergency vehicles are not exempt but have speed limit of  on most roads and  on divided national expressways, unless higher speed limit is posted. Police vehicles are exempt during speeding enforcement.

Enforcement

Speed camera
A threshold for speed cameras in Japan is set at a minimum of  above the limit on an expressway and a minimum of  above the limit on other streets, where drivers will face criminal charges instead of traffic infractions. This is due to legal precedents dating back to 1969 restricting police from filming an individual unless a criminal offence is immediately being committed.

Police enforcement
Although there is no official tolerance for exceeding the speed limit, most drivers in Japan tend to drive over the speed limit on major roads. Police enforcement varies depending on the jurisdiction, officers, traffic flow and street types, but  above the speed limit on an expressway and  above the limit are generally tolerated on other streets.

In 2020, a total of 1,162,420 speeding tickets were issued across Japan, and only 199 tickets were issued for speeding between  over the limit. Of the 199 tickets for speeding  over the limit, Iwate Prefectural Police alone issued 166 tickets. For speeding between  over the limit, Hokkaido, Aichi, Kyoto, Osaka and Fukuoka had the largest shares of tickets issued.

In contrast, Okinawa did not issue any tickets for speeding between  over the limit. Tokyo Metropolitan Police issued a total of 68,693 speeding tickets, but gave out only seven tickets for speeding between  over the limit. Some jurisdictions, such as Tokyo Metropolitan Police, release traffic enforcement locations on their websites.

Speed limit guidelines
In Japan, speed limit cannot be set higher than  for any streets with at-grade intersection or where pedestrians or cyclists are permitted. In other words, the street must be converted to controlled-access highway with costly grade separation to achieve speed limits higher than . There is also major distinguishment between  and  when setting speed limits and different criteria are used.

Although some surface streets such as viaducts, trunk and bypass roads are built to expressway standards, many are not legally classified as expressways and are typically distinguishable by the colour of direction signs: surface streets use blue direction signs while expressways use green signs.

Surface streets
Speed limits for surface streets are set within ± of the reference speed limit below. Reference speed limits do not apply to expressways.

Expressways
Speed limits for expressways are set at  or lower speed. The speed limit is set with the lowest "structure compatible speed" (構造適合速度, kōzō tekigō sokudo) criteria below, that is based on design speed in some factors. Unlike surface streets, there is no range such as ±10 km/h, but the speed should be "respected".

Intercity expressways typically have higher speed limits, while urban expressways within major cities often have  limits and two-lane expressways, typically in rural and remote areas, have  limits for simplified division such as guide posts and  limits with physical separation.

Most expressways outside of cities have active variable speed limit signs and maximum speeds are lowered according to road conditions such as congestions, accidents, constructions and severe weather. When the statutory speed limits are in effect on national expressways, variable speed limit signs are left blank to indicate the statutory speed of  for trucks over 8 t and  for other vehicles. Two sets of variable speed limit signs are installed when the regulatory speed exceeds statutory speed of  on national expressways or  on other roads to regulate the maximum speed of trucks, trailers and three-wheelers to .

Even some 4-lane expressways have  speed limit, there is no  speed limit although it is allowed.

Speed limits can be set at maximum  if it has low crash rates, both structure compatible speed and design speed is 120 km/h, the length is  or more.

lane width (3.5 m ≤ : 120 km/h, < 3.5 m : 80 km/h)

shoulder width (1.75 m ≤ : 120 km/h, < 1.75 m : 80 km/h)

References

Japan
Road transport in Japan