In Singapore, there are copious highways but only a select few are lucky enough to shelter caches. In this case, the CTE (Central Expressway) is one of the chosen few. While placing a cache in the middle of the road is a bit dangerous there are many places around it with hidden crevices.
The Central Expressway (CTE) in Singapore is the major highway connecting the city centre of Singapore with the northern residential parts of the island, including Toa Payoh, Bishan and Ang Mo Kio and further onwards to the Seletar Expressway and the Tampines Expressway.
As of 9 December 2013, the SLE and CTE are one of the two pairs of expressways in Singapore which are linked together, the other being the KPE and MCE.
There are many cars driving up and down so it is hard to act suspicious without being detected. Good luck and have fun.
Little hint: Link