The purpose of
COE was to reduce/control the number of car owners and thus ease up traffic congestion. Therefore, possibly the method thought up to alleviate the congestion problems on public transport would be to increase transport fares.
In near future SG will emulate China where you see tons of people riding bicycles to work. Lol. Quite cool no? The rich would be driving, the middle-incomers taking public transport, and the less-fortunate people like us = bicycles/walk/trishaws