Barrie is one of the seven train lines of the GO Transit system in the Greater Toronto Area, Ontario, Canada.

[4] The line opened on May 16, 1853, when passenger train service began operating between Toronto and Aurora (then Machell's Corners).

[3] On October 11, 1853, service was extended to Allandale, then opposite Barrie on the south shore of Kempenfelt Bay.

In 1968, MPP William Hodgson introduced a private member's bill to move that the government of Ontario establish GO Transit services north of Metro Toronto.

[8] John Crawford Medcof, operating a company named Railroad Boosters, rented a train for one-day service between Barrie and Toronto on 16 October 1969,[9][10] earning a profit.

[13] In 1973, the Canadian Transport Commission held a public hearing at Georgian College[13] during which its three-member committee heard presentations from Medcof and councillors from all "municipalities between Toronto and Barrie".

[14] All presentations favoured the creation of commuter train service between the two cities, including that of York—Simcoe MP Sinclair Stevens.

[14] On April 1, 1972, CN introduced commuter service from Barrie to Toronto, as required by the Canadian Transport Commission.

[15] In the early 2000s, GO Transit opened three new stations on the line: Rutherford on January 7, 2001;[15] York University on September 6, 2002;[16] and East Gwillimbury on November 1, 2004.

[25] The summer service cost CA$520,000 to operate, including train crews, safety and enforcement, station staffing and fuel.

[35] In order to increase service frequency on the Barrie line, GO Transit identified the need to remove the diamond and build a grade separated crossing.

In 2015 Metrolinx initiated a Transit Project Assessment Process (an environmental assessment process specific to transit projects) based on the preferred option of constructing an overpass to carry the GO line over the east-west CP Rail line.

[35] The grade separated crossing (which Metrolinx calls the Davenport Diamond Guideway[36]) is on a 1.4-kilometre (0.9 mi) long, 8.5-metre (28 ft) high rail bridge.

The bridge will allow GO Transit to run all-day, two-way service on the Barrie line without freight traffic disruptions.

[39][needs update] At the same time of building the guideway, further community improvements were added in the immediate vicinity, including noise wall and bearing pads, a rail overpass above Wallace Avenue and a pedestrian underpass at Paton Road, as well as a replacement of the Bloor Street West bridge.

The Barrie line makes connections with: In April 2015, the government of Ontario announced that as part of a broad GO Transit expansion project called Regional Express Rail, service on the Barrie line would increase from 7 daily train trips to over 20 daily train trips by 2020.

[50][a] The railway electrification system was planned to be completed by 2024 and feature two-way, all-day service every 15 minutes between Union Station and Aurora GO.

[59] Stations have been approved in Vaughan for the Kirby Road site (serving the community of Hope), at Mulock Drive in Newmarket, and in Innisfil.

[64] Metrolinx is considering a station in Innisfil for a future expansion, to be located at approximately mile marker 52 (kilometre 83.7).

[67] To provide an interchange with Viva, a bus rapid transit service in York Region, a new station was proposed at Highway 7.

[68] The city of Vaughan has integrated the station into its design plans for a mixed use development near the intersection of Highway 407 and the rail corridor.

[69] In January 2013, Vaughan municipal clerk sent a Vaughan City Council resolution to York Regional Council requesting Metrolinx consideration for four priority projects, among them all-day two-way service on the Barrie line, creation of the Concord GO Station, and creation of a Kirby Road GO Station.