Introduced in May 1997, it was a Peak hour one-way service. From Hougang Central interchange to Penang Rd in AM peak and from Anson Rd to Hougang Central interchange in PM peak. In 1999, extended to ply Marina Centre and converted to loop service. Short route (Express 501X) was introduced at the same time to loop at Marina Centre. In Sep 2000, extended to Sengkang interchange. Withdrawn on Sunday 27 Jul 2003, under NEL rationalisation phase 2.
Introduced in 20 May 1997. From Hougang Central to Boon Lay.
In September 2000, extended to Sengkang.
On 27 July 2003, shortened to Marina Centre, losing their northern part due to North East Line Rationalisation. They farewelled their usage of Hyundai Trajet, Honda Odyssey and Toyota Corolla.
On 2 July 2005, skipped Orchard Link and diverted via Grange Road.
On 26 December 2005, making it more flexible express; this service was diverted via Toh Guan Road, PIE, Stevens Road.
On 12 May 2013, calls at additional stops along Bayfront Avenue and Marina Station Road towards Marina Bay, and AYE; skipping Raffles Avenue, Stamford Road, Orchard Boulevard and PIE itself due to the congestion.
Introduced in May 1997. Peak hours one-way service. From Bedok to Microsoft @ Suntec City in AM peak. From Microsoft @ Suntec City to Bedok in PM peak. In Sep 1999, amended and re-numbered Express 505.
Re-numbered from Express 503 in Sep 1999. Loop service between Pasir Ris interchange and Maritime Square (John Chen Seow Phun's area). In Sep 2000, amended and re-numbered Express 518.
Introduced in 1998. Between Jurong East interchange and Bedok interchange. In 2000, extended to Changi Airport PTB. On Sunday 15 Sep 2002, shortened back to Bedok interchange.
Introduced in 1998. Peak hours one-way service. From Jurong East to Shenton Way in AM peak. From Anson Rd to Jurong East in PM peak. No route change. Withdrawn on Sunday 22 Aug 2004 due to poor demand, replaced by 183 and even the fast forward 97E replaced the rival.
Peak hours one-way service. From Sengkang terminal to Dhoby Ghaut in AM peak. From Outram Rd to Sengkang terminal in PM peak. In Sep 2000, shortened to Hougang Central interchange with the extension of Express 501 and re-numbered Express 511.
Re-numbered from Express 508 in Sep 2000. Peak hour one-way service. From Hougang Central interchange to Dhoby Ghaut (Winsland House) in AM peak & from Outram Rd to Hougang Central interchange in PM peak. No route change. Withdrawn on Sunday 27 Jul 2003, under NEL rationalisation phase 2.
Introduced in Sep 2000 with the extension of Express 502. Peak hour one-way service. From Hougang Central Interchange to Orchard Rd in AM peak & from Moulmein Rd to Hougang Central Interchange in PM peak. No route change. Withdrawn on Sunday 27 Jul 2003, under NEL rationalisation phase 2.
Introduced in 17 December 2011 under the Bus Services Enhancement Programme (BSEP), running from Tampines West all the way to Shenton Way and Gardens by the Bay; which is under Skyfall Cars.
Re-numbered from Express 505 in Sep 2000. Loop service between Pasir Ris interchange and Orchard Rd/Marina Centre with the Orchard Road section cut on 16 June 2006.
On 26 April 2013, the service was extended to Marina Bay Sands.