In addition to its role of funneling through-traffic around downtown Markham, the route serves as a boundary to residential development as land to the north and east are part of the protected Rouge National Urban Park and southwest limits of the planned Pickering Airport.

Donald Cousens Parkway and a planned connection with Morningside Avenue in Toronto form an "East Metro Transportation Corridor", originally envisioned by the province in the 1970s as a six lane municipal expressway.

Although York Region had intended for a continuous alignment, the Toronto City Council has opposed the direct connection between Morningside and Donald Cousens Parkway.

[4] The route intersects 14th Avenue (York Regional Road 71) and continues as before, eventually curving north and meeting Copper Creek Drive while departing from the railway tracks and park.

[4] It encounters Highway 7, north of which it becomes a divided roadway travelling on the eastern edge of Cornell as well as parallel to and alongside Reesor Road.

Approaching and intersecting 16th Avenue, the road makes a broad sweeping curve northwest, continuing to serve as the boundary of urban development in Markham.

[3] A future extension, will carry Donald Cousens Parkway north, crossing over the Stouffville GO Train line on a new bridge and merging into the current southern terminus of Highway 48.

[6] As a result of this, Highway 48 and Donald Cousens Parkway (York Regional Road 48) will become the through route while Main Street will meet them at an intersection demarcating the two.

[15][16] In July 2014 it was announced that Toronto and York would begin sharing jurisdiction over 1.5 km (0.93 mi) of Steeles west from Ninth Line in order to move forward on the planned widening project.

[17] In the interim period since the debate erupted in 2005, York Region and the Town of Markham began collaboration on linking Donald Cousens Parkway between Steeles and Highway 407.

The Box Grove Bypass was constructed by the town beginning in 2005 and opened in the spring of 2007, partially utilizing the Donald Cousens Parkway alignment along the north side of the CP Havelock railway subdivision.

[19] Although a short portion between Copper Creek Drive and Highway 407 — including the unfinished ramps at the interchange — was opened by 2011,[20] the remainder of the project was delayed by issues involving a new railway crossing along 14th Avenue.

York Region planned for a continuous connection between the bypass and Morningside, meeting Steeles Avenue west of its intersection with Ninth Line.

[22] Donald Cousens Parkway will be extended north from Major Mackenzie Drive to tie in with Highway 48, becoming the through-route in the process and completing the Markham Bypass.