To the north of Toronto is the #401 Macdonald Cartier Freeway, which connects Windsor, London, Kitchener, Toronto, Kingston, and Montreal. This 12 lane highway built in the early 1960s when the area was still half urban and rural. Contrary to popular mis-conception (likely because of its size and traffic), the 401 IS NOT the "trans-Canada Highway". The 401 has "express" lanes on the inside for those not needing access to the next few exits, and the "local" lanes at the outside for those planning to exit from the 401 within the next several exits. Every few exists is an interchange area for cars to switch between the local and express lanes.
In the east, the 401 intersects the 404 Don Valley Expressway, which connects into the Don Mills business area as well as downtown Toronto. The 404 also continues north to Newmarket and Aurora.
To the west, beside Yorkdale Shopping Centre, the 401 has a "spaghetti junction" with the Allen Expressway into the inner city of Toronto (it only continues as far south as Eglinton), and has the TTC Subway line between the lanes of roadway.
Further west, near Jane Street, the 401 connects with Highway 400, the major roadway to Barrie and Ontario's cottage country, as well as to the Transportation-Canada Highway at Sudbury and North Bay.
Just west of the Humber River, the 401 connects to Highway 409 which continues into Pearson International Airport, and to Highway 427 South which connects to the Queen Elizabeth Way (QEW) west to Oakville and Hamilton, which east of the 427 is the Gardiner Expressway which winds along Toronto's lakefront into the downtown core.
More about the highways
Addresses west of Yonge Street are numbered from Yonge street and suffixed "West" and addresses east of Yonge Street are numbered from Yonge Street and suffixed "East".
There is no consistency in numbering in a north-south direction, partly because of a curving lakeshore and the different municipalities that became the City of Toronto.. Along Yonge Street, the numbering at the cross-streets is roughly: Eglinton 2500, Lawrence 3000, York Mills/Wilson 4100, Sheppard 4800, Finch 5600, and Steeles 6400.