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The county is served by Highway 401 in the south, Highway 7, a leg of the Trans-Canada Highway, in the central region, Highways 62 and 37 travelling north to south, Highway 28 travelling east to west in the northern region, and Highway 127 travelling north from Maynooth, also in the northern region.
In addition, between Leslie and Bessarion stations, a former Canadian Tire warehouse/distribution centre next to Highway 401 (the chain retains a store nearby, along with Mark's Work Wearhouse, also owned by Canadian Tire) was demolished and the land was being sold to Concord Adex Investments Limited of Vancouver.
The Thousand Islands Bridge connects New York State and Ontario by traversing Wellesley Island at the northernmost point of Interstate 81 in Jefferson County and meets Highway 137, which leads to Highway 401.
The creek flows south under Highway 401, loops west then back east under the Canadian National line, and turns east at the Scarborough RT line west of Midland Avenue.
The East Durham Link is one of two proposed freeways to connect the future east extension of Highway 407 with Highway 401; the West Durham Link, to be located to the west in Whitby, is the second.
In 1963, it was announced by MacNaughton that Highway 401 would be widened from a four-lane highway to a collector-express system, modelled after the Dan Ryan Expressway in Chicago.
The terminal mainly supports GO Transit's bus services east and west across the Highway 401 corridor and is adjacent to York Mills station on the Yonge-University-Spadina line of the Toronto Subway.