Singapore manages traffic demand through ownership pricing in the form of an Additional Registration Fee (ARF) which, coupled with the city's Vehicle Quota System (VQS), helps limit increases in congestion.

The ARF was introduced in 1972 to deter vehicle ownership, and was raised by 9% each year between 1972 and 1989. The final amount of the ARF is based on a percentage of Open Market Value (OMV) of vehicles:

• Cars and taxis: 100%
• Motorcycles: 15%
• Commercial vehicles & buses: 5%

VQS was introduced in 1990 to control the growth of vehicle ownership, and increased 3% a year through 2008, before dropping to a 1.5% increase per annum in 2009. VQS requires a Certificate of Entitlement (COE) to own a vehicle, which expires after ten years. COEs are available through an open bidding system.

Without ARF & VQS, car population is projected to have grown an additional 83% by 2008, resulting in Singapore's lower rate of car ownership compared to other major international cities like New York, Tokyo, London, and Paris, affording for greater flexibility in congestion management. This decrease has led to a reduction in 14,500 ktonnes of oil equivalent (ktoe) consumed and 42,500 ktonnes (3.8% annual reduction) of CO2 emissions.

http://singapore.xpatxperience.com/vehicles/singapore_coe.shtml