Basic bus services are the main form of bus services being offered in Singapore, providing daily bus connections across the island with a vast network of bus routes. There are over 300 trunk routes in Singapore, with more under planning under the Bus Services Enhancement Programme (BSEP).
Currently, basic bus services are offered by public transport operators (PTOs) SBS Transit, SMRT Buses, Tower Transit as well as Go-Ahead, each with their own areas of responsibility. They usually operate between 5:00 am to 1:00 am the next day, with selected routes having extended operating hours during eves of Public Holidays.
There are two main forms of basic bus services: Trunk services and Feeder services.
Trunk & Feeder Services
Trunk services form the backbone of the public bus network. These are long bus routes that connect different neighbourhoods or towns across the island, or into the City areas.
Feeder services operate around a neighbourhood. They usually operate out of a bus interchange, providing connections to various parts of housing estates, and are key to the hub-and-spoke transport system of Singapore.
Closely associated with their parent services, Route Variants serve similar catchment areas and are operated either within or outside their parent service’s operating hours. Some are supplementary routes introduced to ply crowded stretches of their parent trunk routes, operating alongside them either full-day or only during the weekday peak hours. Others operate outside of their parent service’s operating hours (e.g. weekday nights and weekends), plying slightly different routes. Short-Trip services are short-haul trips that operate only along a segment of their parent route and incorporate the suffix A, B, C and even W.
Terminating Trips will display a “T” suffix to their parent route.
More resources: Bus Service Prefixes and Suffixes | Land Transport Guru