The Executive Council has approved a $1 toll increase for the Tate's Cairn Tunnel from December 25. However, the toll for minibuses will be unchanged, while a $1 promotional discount will be given to empty taxis between midnight and 6am.

With no increase, the tunnel forecasts a 6% internal rate of return over the 30-year franchise period. With an increase, a 6.1% return is expected. In its franchise bid the tunnel was assumed to achieve a 13.02% rate of return.

It is estimated the toll adjustments will divert 500 vehicles to Lion Rock Tunnel per day, and 100 vehicles each to Route 8 and Tai Po Road.