Former Liberal premier Nick Greiner fears the WestConnex motorway has reached a "very sad outcome" and says remaking Parramatta Road should remain central to the controversial project.

Mr Greiner, an architect of WestConnex in his former role as the state's infrastructure chief, was responding to concerns raised at a NSW Parliament transport summit on Tuesday that the $13 billion road project is no longer wedded to new housing and urban renewal – benefits that were once touted as key payoffs to the public for accepting the motorway. The government has rejected the claims.

Choked: Former premier Nick Greiner says Parramatta Road should remain the focus of the WestConnex project. Credit:Tamara Dean

WestConnex, Australia's biggest infrastructure project, will better link Western Sydney to the airport and Port Botany. If built, it will be the largest motorway in the nation's history.

The NSW government says it will take thousands of trucks and cars off surface roads and move them into tunnels, allowing large sections of Parramatta Road and surrounding neighbourhoods to be revitalised.