It sounds like a dream come true for traffic-weary northern beaches residents: buses with speed and capacity to rival trains and a tunnel bypassing one of Sydney's slowest commuter routes.

But these and other options floated by the state government to cut travel times along Pittwater, Spit and Military roads have been criticised as ''inadequate'' by North Sydney Council and divided residents.

Fairfax Media has obtained a number of submissions to Transport for NSW's ''bus rapid transit'' pre-feasibility study to the northern beaches after the department refused to release them.

The study - a Coalition election promise - examined five options between Mona Vale and the city. It included a two-lane tunnel from Spit Junction to the Warringah freeway, establishing 24-hour bus lanes and widening the Spit Bridge to six lanes, potentially closing it to marine traffic.

It also canvassed an east-west option between Chatswood and Dee Why, including widening Warringah Road and improved access to the Chatswood interchange. The study concluded that a package of bus rapid transit measures was feasible, but conceded that prioritising buses by removing general traffic lanes would lead to longer trips for other vehicles.