NSW Premier Barry O'Farrell has rejected a call for pink train carriages for women and children, saying it's more important to provide "real protection".

The NSW Rape Crisis Centre and the Rail Tram and Bus Union (RTBU) want the government to trial the pink carriages on the City Rail network for three months between 7pm and midnight.

The carriages would represent safe zones next to guard carriages exclusively for women and children.

"This option for women and children, with access to the guard and security alarms, may encourage women and children to go out and enjoy all that our city has to offer without being concerned about what may happen on in the train on the way home," the NSW Rape Crisis Centre's Karen Willis said.

RTBU National Secretary Bob Nanva said the system has been successfully used in Brazil, Japan, Egypt, India, Indonesia, Israel and Taiwan.

But Mr O'Farrell says women should feel safe travelling day or night on all carriages.

"I think what's most important for all passengers, but particularly for female passengers, is to have appropriate security across our train system," he told reporters.

"My focus is on getting police transport command controlling our train system - not on carriages that might be painted pink but don't offer any particular protection in the event of a problem," he said.

There were 203 reported cases of sexual assault and other sexual offences on the rail network in 2010, with women aged 18 to 29 most likely to be the victims, the RTBU said.