The first trip that unveil the practicality, economical, feasibility, and time-saving of riding bicycle was from Clementi MRT to Tanjong Pagar area.
The route I took was: Commonwealth Avenue West, Commonwealth Avenue, Leng Kee Road, Tiong Bahru Road, Outram Road, Cantonment Road.
Commonwealth Avenue West between Clementi MRT and Clementi Road is not too nice to ride on because ... there are many busses on it. Between Clementi Road and Buona Vista Road has a relative light traffic. Alternatively, can also get on to the Ulu Pandan Park Connector from Clementi Road for a more relaxing ride but slightly further. Again, be careful on the small stretch of between Buona Vista Road and Holland Avenue where many busses turn left on the left turn only lane.
From here until Tiong Bahru Road is not too difficult as the lanes are wide and traffic not too heavy. Again, there is Alexandra Park Connector for relax riding. I don't recommend Margaret Drive because if I remember correctly, it is narrow and single lane.
A bit tricky from Leng Kee Road to Tiong Bahru Road as car have to make a U-turn at Tanglin Road and Alexandra Road junction, or turn into Alexandra Road earlier and right turn into Tiong Bahru Road. Then, the stretch near Red Hill MRT is narrow, upslope, single lane (I think) is a bad road to ride on. Yet, another very tricky and dangerous part when turning from Tiong Bahru Road into Outram Road.
As such, on most of my subsequent trips, I chose to ride by Alexandra Road, Ganges Avenue, Havelock Road, Upper Pickering Street, South Bridge Road. Alternatively, sometimes I turned into Chin Swee Road then to Outram Road when I felt like burning some fats riding up this road besides the Pearl Hill. I just noticed another alternative that I haven't ridden on, turning right from Ganges Road into Outram Road, probably because I don't like to turn right.