taken from sgWiki.com/wiki/buses:
CSS 1: Marine Terrace Queensway
Via Marine Terr, Marine Parade Rd, Marine Cres, Marine Parade Rd,
Still Rd South, East Coast Rd, Mountbatten Rd, Tg Katong Rd, Dunman
Rd, Old Airport Rd, Stadium Rd, Stadium Walk/Rd, National Stadium
CP B & C, Stadium Rd, Nicoll Highway, Stamford Rd, Orchard Rd,
Penang Rd, Somerset Rd, Grange Rd, Orchard Boulevard, Grange Rd,
Napier Rd, Holland Rd, Queensway (Blk 53)
And return via Queensway, Jln Bt Merah, (u-turn at Hoy Fatt Rd
junction), Queensway, Holland Rd, Napier Rd, Tanglin Rd, Orchard
Rd, Bras Basah Rd, Nicoll Highway, Stadium Rd/Walk/Rd, Old Airport
Rd, Dunman Rd, Tg Katong Rd, Mountbatten Rd, East Coast Rd, Still
Rd South, Marine Parade Rd, Marine Cres, Marine Ter
Operating hours: 0630 1930 hrs except Sundays and Public
Holidays.
CSS 6: Bt Merah Circuit Rd
Via Bt Merah Int, Merah Central, Henderson Rd, Tiong Bahru Rd,
Outram Rd, Eu Tong Sen St, Hill St, Stamford Rd, Dhoby Ghaut,
Selegie Rd, Serangoon Rd, Macpherson Rd, Aljunied Rd, Merpati Rd,
Circuit Rd, Pipit Rd, Circuit Rd.
And return via Circuit Rd, Pipit Rd, Circuit Rd, Matter Rd,
Aljunied Rd, Macpherson Rd, Bendemeer Rd, Jln Besar, Bencoolen St,
Bras Basah Rd, North Bridge Rd, South Bridge Rd, Neil Rd, Eu Tong
Sen St, Outram Rd, Tiong Bahru Rd, Henderson Rd, Bt Merah Central,
Bt Merah Int
Operating hours: 0630 1930 hrs except Sundays and Public
Holidays.