While some sections of Japanese expressways allow speeds of up to 100 km/h (62 mph), the vast majority operate at speed limits between 80 km/h (50 mph) and 70 km/h (43 mph). The majority speed limit, which ranges from 50 mph to 43 mph, should be viewed as the standard for a safe maximum speed.

Kei trucks, vans, and cars are not engineered for fast speeds. Although they are typically very light, weighing 1,500 to 1,600 pounds, the engines are limited to 660cc, which results in their transmissions being geared high. Going or exceeding 62 mph (100 km/h) can easily lead to unsafe driving conditions and excessive engine stress, which the engine was not designed to withstand. Kei trucks are engineered for Japan's smooth and well-maintained roads, where the driving culture is generally less aggressive.