Scarborough is in the east end of the City of Toronto, once its own city. The boundary with Toronto used to be the north-south Victoria Park Avenue. There are a number of major east-west roadways (from the north): Steeles, which is the city limit, Finch, Sheppard, Ellesmere (which continues as York Mills west of Victoria Park), Lawrence and Eglinton.
There is also the diagonally running Kingston Road running roughly parallel to the Lakeshore, which connects the downtown --to the west of Scarborough-- with the 401 east of the city.
The community also has major north-south roadways about every mile, most of which have access from the 401 Highway to provide quick access to all neighbourhoods.
The community is traversed by 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 west, 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.
More about the highways