The six lane tunnelling work proposed in 2015 which will connect Tikuji-ni-Wadi in Thane to Western Express Highway at Borivali will take another six months to start.
The Maharashtra State Road Development Corporation (MSRDC) has yet to obtain approval from the National Wildlife Board to conduct boring operations in Sanjay Gandhi National Park (SGNP).
Delay has been due to lack of forest clearance and work is yet to commence.
The project will entail an investment of Rs 1,500 crore. The 11 km long tunnel which will pass under SGNP is expected to cut the travel time between Mumbai and Thane by 20 minutes.