Singapore implemented several measures in the 1970s and 1990s to manage increasing traffic volumes and car ownership. The Area Licensing Scheme (ALS) required motorists to pay to use certain roads and reduced car numbers. While initially unpopular, ALS was successful. It was later replaced by Electronic Road Pricing (ERP), which used improved technology. The Park-and-Ride scheme encouraged parking outside the city center and taking public transit but was not widely used. The Vehicle Quota System set a monthly limit on new vehicle registrations through a Certificate of Entitlement bidding process, which is still used today to control the car population.