Highway 404 is an Ontario 400-Series Highway that runs from the junction of Highway 401 and the Don Valley Parkway in Toronto to its northern terminus at Green Lane/Herald Road in Newmarket. Originally an extension of the Don Valley Parkway, the 404 became a provincial highway (and was completed by the Ontario Ministry of Transportation) in 1977. The highway mainly serves as a commuter road for those working in Toronto but living in the northern suburbs of the city. Running parallel to Highway 400 approximately 15 kilometres to the east, the 404 extends 36 kilometres north-south. The MTO plans to further extend the 404 northerly (and easterly) to Highway 12, to better serve commuters and to provide an alternate highway link into Ontario's "cottage country."

The 404 has 14 interchanges along its entire length. Its northbound control city is Newmarket (exits 22-45), though no control city is used in the city of Toronto (except at the 401). Its southbound control city is Toronto (exits 53-22), but no control city is used in the city of Toronto. The fact that the exit numbers start at 17 suggest that the Don Valley Parkway was included in distance calculations when signing the exits, although there are no exit numbers posted on the DVP.

Interchanges from South to North

Future interchanges (if the 404 is extended northward)

References

• Cameron Bevers, The History of Ontario's Kings Highways at http://www.thekingshighway.ca/
• Scott Steeves, www.ONTHIGHWAYS.com at http://www.onthighways.com/