Kei car, K-car, or kei jidōsha, is a Japanese category of small vehicles, including passenger cars (kei cars or "kei class cars"), microvans, and pickup trucks ("kei trucks" or "kei class trucks"). They are designed to comply with Japanese government tax and insurance regulations, and in most rural areas are exempted from the requirement to certify that adequate parking is available for the vehicle. This especially advantaged class of cars was developed to promote popular motorization in the post-war era. While successful in Japan, the genre is generally too specialized and too small to be profitable in export markets.


The cars feature yellow licence plates, earning them the name "yellow-plate cars" (black numbers on yellow background for private use and yellow numbers on black background for commercial use) in English-speaking circles. Because regulations only restrict physical size and engine displacement (and latterly outright power), manufacturers have been able to introduce many advanced technologies to the class. As a result, kei cars are often available with forced induction engines, automatic and CVT transmissions, front-, rear- and four-wheel drive, air conditioning, GPS and many other features.

Daihatsu, Honda, Mitsubishi, and Suzuki all manufacture kei cars, while Nissan sells badge-engineered Mitsubishi and Suzuki models, Mazda offers badge-engineered Suzuki models, and Toyota and Subaru offer badge-engineered Daihatsu models. German brand Smart offered a kei version of its Fortwo called the Smart K in Japan at Yanase dealerships from 2001 to 2004 with specially developed rear fenders, reduced tire dimensions and track width, to conform to kei car standards, though ultimately the model sold the fewest examples of a kei car when it was marketed.


360 cc era (1949-1975)

These standards originated in the times following the end of the Second World War, when most Japanese could not afford a full-sized car, yet had enough to buy a motorcycle. To promote the growth of the car industry, as well as to offer an alternative delivery method to small business and shop owners, kei car standards were created.Originally limited to a mere 150 cc (100 cc for two-strokes) in 1949, dimensions and engine size limitations were gradually increased (in 1950, 1951, and 1955) to tempt more manufacturers to produce kei cars. It wasn't until the 1955 change to 360 cc as the upper limit for two-strokes as well as four-strokes that the class really began taking off, with cars from Suzuki (Suzulight) and then Subaru 360 finally able to fill people's need for basic transportation without being too severely compromised. In 1955, the Japanese Ministry of International Trade and Industry also set forth goals to develop a "national car" that was larger than kei cars produced at the time. This goal influenced Japanese automobile manufacturers to determine how best to focus their product development efforts for the smaller kei cars, or the larger "national car".

The class then went through a period of ever increasing sophistication, with an automatic transmission appearing in the Honda N360 in August 1968, with front disc brakes becoming available on a number of sporting kei cars, beginning with the Honda Z GS of January 1970. Power outputs also kept climbing, reaching a peak in the 40 PS (29 kW; 39 hp) Daihatsu Fellow Max SS of July 1970. Sales increased steadily, reaching a peak of 750,000 in 1970. Throughout the 1970s the government kept whittling away at the benefits offered to kei vehicles, which combined with ever stricter emissions standards to lower sales drastically through the first half of the decade. Honda and Mazda withdrew from the contracting passenger kei car market, in 1974 and 1976 respectively, although they both maintained a limited offering of commercial vehicles.

Until 31 December 1974, kei cars used smaller license plates than regular cars (230 x 125 mm). As of 1975, kei cars received the medium sized standard plates (330 x 165 mm). To set them apart from regular-sized cars (non-kei), the plates were now yellow and black rather than white and green.

550 cc era (1976-1990)

Sales had been steadily declining, reaching a low water mark of 150,000 passenger kei cars in 1975, eighty percent less than 1970 sales. Many were beginning to doubt the continued existence of the kei car, with both Honda and Mazda withdrawing in the middle of the seventies.

The even stricter emissions standards which were to be introduced in 1975 as part of a staggered program of cleaning the air proved problematic for kei manufacturers. This was particularly hard for Daihatsu and Suzuki who focused on two-stroke engines. Tiny Suzuki was worst off, with the company's entire production consisting of two-stroke engined kei cars. Daihatsu, on the other hand, had both the engineering backing and powerful connections of their large owner Toyota to aid them in meeting the new requirements. All manufacturers of kei cars were clamoring for relaxing the dimension conditions, claiming that the emissions standards could not be met with a functional 360 cc engine (even though Subaru's SEEC-T equipped Rex proved it possible). In the end, the Japanese legislature relented, increasing the overall length and width restrictions by 200 mm and 100 mm respectively. Engine size was increased to 550 cc, taking effect from January 1, 1976. The new standards were announced on 26 August 1975, leaving very little time for manufacturers to update their offerings.

Most manufacturers were somewhat surprised by the decision: having expected a 500 cc limit, they had already developed new engines to fit such restrictions. These new engines were quickly introduced, usually mounted within widened bodies of existing models. These interim versions (with displacements ranging between 443 and 490 cc) were "feelers", developed to see if there was indeed a continued market for the kei car. As sales improved, they only lasted for a model year or so until manufacturers had had the time to develop "full-size" engines. Only Daihatsu managed to avoid developing transitional engine versions which did not take full advantage of the new regulations. Kei car sales remained stagnant however; while combined passenger and commercial kei car sales reached 700,000 for the first time since 1974, in a quickly growing market the small cars still lost market share.

As the vehicles became better and more capable, another benefit appeared, as exports increased considerably. In particular, export sales of trucks increased, while kei passenger car exports increased at a lower rate. In 1976, exports of keis were 74,633 (up 171 percent year-on-year), despite exports of passenger kei cars decreased. 1980 was another record year as exports climbed 80.3 percent (to 94,301 units), of which 77.6% were microtrucks. Nearly 17% of exports went to Europe, dwarved by Chile which took nearly a quarter of the exported keis. In a tough economy, economic cars sold well and 1981 marked another banner year as Japanese midget car sales reached their highest since the 1970 record (at 1,229,809 units for cars and commercials). As the eighties progressed, kei cars became increasingly refined, losing their utilitarian origins as Japanese customers became ever better off. All kinds of technical improvements, from four-wheel drive to turbochargers to air conditioning began appearing in keis.

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