Common alternatives to private vehicles include bicycles, bus, taxis and train (MRT or LRT). Two companies run the train transport system—SBS Transit and SMRT Corporation. Four companies, Go-Ahead, Tower-Transit, SBS Transit and SMRT Corporation run the public buses under a 'Bus Contracting Model' where operators bid for routes. There are six taxi companies, who together put out over 28,000 taxis on the road. Taxis are a popular form of transport as the fares are relatively cheap compared to many other developed countries.