If i remember correctly, Clementi interchange dun allow any
alighting after 1997, before that alighting was allowed. At that
time, there was a plate on the bus stop (the one before the mrt bus
stop) and the mrt bus stop telling passengers taking services that
terminate at clementi to alight at the mrt stop, whch i think was
quite stupid. i dunno whether they r still there or not. but
anyway, i think why sbs did this was because not many passengers
alight at the interchange, most alighted at the mrt bus stop.
moreover, preventing alighting inside the interchange may help in
easing jams inside the interchange. as you all know, clementi
interchange is very small and cramped.