A city-bound bike path that was to have offered a separated route toward the central business district along the WestConnex motorway will be closed to cyclists when Sydney Olympic Park is busy.

The Herald reported on Monday that although traffic and pollution modelling for the M4 East part of WestConnex was conducted on the assumption that public transport would be improved on the adjacent Parramatta Road, Transport for NSW is giving itself up to five years to implement any upgrades.

Construction workers in the almost-completed M4 East tunnels. Credit:AAP

Measures that should have been built into WestConnex to make it easier for western Sydney cyclists to ride toward the CBD will also be suspended for parts of the year, for instance during the Easter Show.

The Sydney Motorway Corporation, the private entity created by the government to contract and build the motorway, wrote to advocacy group Bicycle NSW in February to say that an eastbound cycleway included as part of the M4 East section of WestConnex would be closed to cyclists during major events at Sydney Olympic Park.