Roads Minister Duncan Gay has all but confirmed his government will build a light rail line from Parramatta to Sydney Olympic Park.

Announcing the construction of a westbound off-ramp from the M4 Motorway at Hill Road as part of the redevelopment of an industrial area in Lidcombe, the minister appeared to spill the beans on the government's light rail plans.

"Increasingly this is going to be a residential area, we need to look after them," Mr Gay said when asked about congestion in the Sydney Olympic Park area.

"We will be having light rail, that will be coming through this sector. There are bus routes and this will be an improvement of the road infrastructure which will be linking with WestConnex which will be opening stage one in 2019.