The Electronic Road Pricing (ERP) system is an electronic toll collection scheme adopted in Singapore to manage traffic by way of road pricing, and as a usage-based taxation mechanism to complement the purchase-based Certificate of Entitlement system. The ERP was implemented by the Land Transport Authority on April 1, 1998 to replace the preceding Singapore Area Licensing Scheme (ALS) that was first introduced on 11 August 1974 after successfully stress-testing the system with vehicles running at high speed. The system uses open road tolling; vehicles do not stop or slow down to pay tolls.