To the south of Woodstock, Highway 401 curves northeast and encounters the western terminus of Highway 403.
After this 10 km (6.2 mi) gap, the highway interchanges with the Highway 407 Express Toll Route.
Within the GTA, the highway passes several major shopping malls including Yorkdale Shopping Centre, Scarborough Town Centre and Pickering Town Centre.
giving the highway a wide span and four carriageways.
The highway curves northeast and follows a power transmission corridor to Highway 409, which merges with the mainline and forms the collector lanes.
It returns to its eastward route through Toronto, now carrying 12–16 lanes of traffic on four carriageways.
Near Tilbury, Highway 401 loses its tall wall median barrier and narrows to four lanes, following lot lines laid between concession roads in a plan designed to limit damage to the sensitive agricultural lands through which the highway runs.This area is not as flat but the highway is generally straight.This part of Highway 401 often experiences heavy snowsqualls in early winter, sometimes extending as far east as Toronto.These three sections of highway were 11.8, 54.7 and 41.2 km, (7.3, 34.0 and 25.6 mi), respectively.In 1964, the route became fully navigable from Windsor to the Ontario–Quebec border.