The inspection system is in place to ensure cars on Japanese roads are properly maintained and are safe to be on the road. Another reason is to determine if a car has been illegally modified . Illegally modified vehicles and vehicles deemed unsafe by police will have a red sticker with the following: (Illegal Vehicle) in yellow and the date the vehicle was declared not fit to be on the street.
Before a test can be administered on a vehicle the owner of the vehicle must call up a Shaken center and make an appointment by phone after which the owner must fill out paper work at the center. The cost for the Shaken is broken up as follows: 1,400 yen for paperwork and processing, 25,200 yen for the testing, 29,780 yen for 24 months of validity and 8,090 yen for "Recycling Department" with fees being added depending on the vehicle and it's intended use (business, personal, commercial, etc.). These variables can result in a shaken costing from 100,000 to 150,000 yen or more. In comparison to the costs of the shaken a full diagnostic inspection of the very same Japanese models in the U.S. may cost less than $100 USD (11,800 yen).
The process of the shaken is very simple and the following tests and steps are as follows for government inspection testing (however a licensed garage can also do this):
Should a car not meet any of the tests it will have to be repaired and retested before passing.
The speedometer of the car will be tested by driving up on to a dynamometer. The vehicle will be propelled to 40 km/h twice and the vehicle's engine rev amount will be recorded, should the vehicle have different numbers it will not pass.
All headlights must be aligned to be in a straight line with their height on the car. Halogen, HID and bulb style head lights are allowed. All headlights must have the same color when turned on. Headlight swaps, making pop-up headlights into normal headlights, rally-car style multiple headlights and putting trim around headlights is allowed.
Cars that are 10 years and newer must have carbon monoxide measurements of 1% and hydro-carbon output of 300ppm. Cars older than 10 years must have carbon monoxide measures of 4.5% and hydro-carbon output of 1200ppm. High flow catalytic converters are allowed however gutted ones are not. All O2 sensors must be in working order along with any oil catch tanks. Mufflers when tested for noise output will be tested at a 45 degree angle at a 50 cm distance. For vehicles 10 years and younger the max level allowed is 96 dB (decibels). For vehicles over 10 years of age the max level allowed is 103 dB.
All bushings must not be broken or in bad condition. All control arms must be in working order. There can be no rust/corrosion on springs, struts or other suspension components. If the car has 4 wheel steering it must be working. The vehicle must also meet minimum height requirements which will be checked by referencing the lowest part of the vehicle (not including the suspension components). For vehicles with 200-249 cm wheelbase they must be 8 cm off the ground and vehicles with 250-299 cm wheelbase they must be 9 cm off the ground. For all other vehicles for every 50 cm over 299 cm in wheelbase add .5 cm to the minimum height and for vehicles under 200 cm in wheelbase subtract .5 cm to the minimum height.
General interior equipment must be still intact (ie: dash). Roll cages (must have padding around bars) and carpet removal are allowed. Bucket seats must measure 420 mm from left to right bank but can not be over 450 mm from left exterior side to right exterior side (total width of seat). Aftermarket seats made of fiber-reinforced plastic are not allowed. Any holes or rips in seats must either be taped up or repaired.
Many people create workarounds in order to have a vehicle that is otherwise illegal pass its "shaken". Some of the typical workarounds are putting flanges in the exhaust that are mostly metal with a few holes drilled, airing up the tires more in order to gain height for the vehicle, putting ceramic pipe between the spring and the spring's seat in order to raise vehicle height (this is commonly done on lowered coilover suspensions), reconnecting exhaust gas recirculation devices, removing injector connectors from the ECU (engine control unit), taping off parts of the headlight's housing in order to make the headlights look correct, cleaning the underside of the vehicle to hide signs of oil leaks and trapping the speedometer so it registers the same numbers when tested on the dynamometer.
Contrary to what is common amongst Western tuners towards vehicle regulations, many Japanese tuners respect the "shaken" and want to tune within its boundaries. In JDM Insider Volume 3: Kansai Adventure part 1 they visit a tuning shop called "Phonenix's Power SPL" (a shop specializing in only legal modifications) and met with the owner who when interviewed talked about how the people who originally did modifications were the outlaws but since they made it legal to modify in Japan many professionals and regular people have started modifying their vehicles and have started to embrace the regulations set on cars so they can continue to enjoy their hobby legally.
As vehicles get older, maintaining them at the standards required by the shaken can become expensive. This is because beyond the tuner scene, most Japanese do not get involved in mechanical repairs, and as a result, mechanics can charge high prices. Vehicles which cannot pass inspection are not allowed to be driven on public roads. Unwanted vehicles must be destroyed and recycled, or as some do to make more profit, export the vehicle. As a result, many Japanese used vehicles are exported to other nations right before or after their Shaken is up.