i think one of the reason why jams occur on xpressways are when there are too many heavily used entrance/exits that are too near each other.... u have cars trying to come in, go out...
for us, it starts between this stretch punggol->lor halus->pasir ris..... quite similar to the cte stretch between bradell->amk1->amk3....
actually, there are plans to connect punggol to pasir ris like punggolboy's suggestion.. hehe
just dunno when they do it... can see ura masterplan 2003.
http://spring.ura.gov.sg/dcd/eservices/sop/main.cfm?view=mpview (need to zoom in to see)