Highway 400 Widening North of Highway 9 Moves to Detailed Design

This report by Editorial team is based on information published by Government of Ontario.

According to the Government of Ontario, a detail design contract has been awarded for widening Highway 400 between Highway 9 and the future Bradford Bypass, also called Highway 425. The plan would take this eleven-kilometre stretch from six lanes to ten, adding one general-purpose lane and one high-occupancy vehicle lane in each direction.

The design work is wider than pavement alone. The province says the contract covers culverts, signs, drainage and storm sewers, lighting and interchange ramps along the corridor. Those elements matter because widening a highway through King Township also means managing water flow, farm and local road access, and connections at existing interchanges while traffic keeps moving.

Where this fits in the corridor

Drivers in Vaughan, King and communities farther north already use a recently widened section of Highway 400. Ontario says it has completed widening nine kilometres from Major Mackenzie Drive to King Road, and work tied to future widening in Barrie includes replacing the Dunlop Street bridge. The new design section would extend the high-occupancy network northward to meet lanes that already exist south of Highway 9.

The province also says major construction on the Bradford Bypass began in May 2026. The Highway 400 design therefore sits between two moving pieces: an upgraded corridor to the south and a new east-west route intended to connect Highway 400 with Highway 404. No opening date for the widened King section is given in this announcement, and readers should not treat design work as the start of full construction.

Why design comes before construction

Detailed design turns a corridor concept into drawings a builder can price and construct. That stage settles lane geometry, structures, drainage, utility moves and staging so traffic can be kept moving during construction. For residents, the practical sign to watch for next is not a ribbon cutting but further provincial notices about design milestones, property or utility work, and eventually a construction contract.

Local effect while work is still on paper

For now, daily driving does not change. The importance for York Region commuters and freight operators is longer term: Highway 400 carries trips between Toronto, Vaughan, cottage country and northern Ontario, and congestion on it spills onto regional roads such as King Road and Major Mackenzie Drive. Any future construction staging will need its own notice, and this report will be updated if the province publishes construction dates on the source page linked below.