GPS is an innovative technique for an electronic road pricing (ERP) system. By using GPS technology, ERP systems will be extremely efficient and cost-effective. This paper describes the next generation of ERP in Singapore and proposes a GPS based multi-sensor positioning system for ERP vehicles. Multi-sensor fusion algorithms are presented for the integration system. The integrated positioning system (IPS) developed in this paper makes it possible to realize GPS based ERP with a simple composition and low cost.