The Toronto Transit Commission (TTC) maintains five rapid transit lines and 109 stations on of route.
The TTC's heavy rail linesLines 1, 2, and 4are built to the unique Toronto gauge of , which is the same gauge used on the city's streetcar system. However, the former Line 3 Scarborough light metro system (which operated between 1985 and 2023) used standard-gauge track, which is also used for the two light rail lines, Line 5 Eglinton and Line 6 Finch West, and the under-construction Ontario Line.
Tunnels are either square or round, depending on the method of their construction: Square tunnels were built with the cut-and-cover method of digging trenches down from the surface, constructing the tunnel structure, and then backfilling. Round tunnels are bored using a tunnel boring machine (TBM). The cut and cover technique was used extensively on the oldest portions of the system, while newer sections were predominantly orin the case of the TorontoâÂÂYork Spadina subway extension (TYSSE) and the underground portions of Line 5 Eglinton, which opened in 2017 and 2026 respectivelyentirely bored.
Some sections of track run on the surface, such as the stretch of Line 1 YongeâÂÂUniversity in the median of Allen Road. The former Line 3 was a surface or elevated route for nearly its entire length.
Diamond crossovers (or "scissors crossovers") are X-shaped track assemblies that are used on Lines 1, 2, and 4, particularly at terminal stations, to allow trains to switch to the opposite platform or track to reverse direction. They also exist at some through stations (mostly those that were former terminal stations before extensions) where they are often used to short turn trains. A single crossover just east of Union Station is what remains of a former diamond crossover, which was used when the station marked the southern terminus of the original line.
Line 5 Eglinton and Line 6 Finch West use, in some locations, a pair of single crossovers (one facing-point and the other trailing-point) or sometimes just a single crossover (either facing-point or trailing-point) instead of diamond crossovers.
Crossovers are found in the vicinity of the following stations. Unless otherwise described, they are diamond crossings.
Centre tracks allow a train to enter from either end into a third track, longer than the length of a standard train, between the two service tracks. Trains can either layover or short turn there, allowing other trains to pass them by, or reverse direction from this position with minimal interference with through trains compared to crossovers, which requires the reversal to take place on station platforms. Sometimes, in-service trains are diverted into centre tracks when there is track maintenance on one of the service tracks. Pocket tracks are a variation on the centre track, accessible only from one end. Some storage tracks have a short stub extending beyond the convergence back to the service tracks used to store work cars. Most centre-track structures were built using the cut-and-cover method, and there are support columns between the tracks. However, Finch West station, which was partially bored, has three fully separate tunnels, and and stations, which were "mined" using the sequential excavation method rather than excavated, have all three tracks housed within single tubular, columnless tunnels.
Storage tracks are found in the vicinity of the following stations:
Track configurations become more complicated where lines meet (at the SpadinaâÂÂSt. GeorgeâÂÂMuseumâÂÂBayâÂÂYonge junction and at SheppardâÂÂYonge), and at the entrances to subway yards.
On Lines 1, 2, and 4, tracks usually continue for roughly the length of a train beyond the last station on a line; these are known as tail tracks. The only exception to this is at Don Mills station, where the tail tracks are less than two cars in length. This is likely because storage capacity is available at SheppardâÂÂYonge, which can store enough trains to service the line. The tail track structures at some terminal or former terminal stations also have, or have provisions for, a third tail track. Finch station has such a triple configuration, Vaughan Metropolitan Centre station is a terminal station with a trackless tunnel section for installation of a potential third tail track, and Sheppard West station was a former terminal also built with a trackless third tunnel north of it, which could now accommodate a future standard pocket track.
Other track features that exist include the following:
The Bloor wye was used for interlining between Lines 1 and 2 in 1966:
The tracks used for access to yards:
The Sheppard Wye allows the movement of out-of-service trains between the Sheppard line and the Davisville Yard on the Yonge line. The wye has the following features:
Each Line 1, 2, and 4 yard has different features that join them to the mainline. Operators generally board their train at a point where the yard meets the main line, at the Greenwood Portal, the Davisville Buildup (third platform of Davisville station), or the Wilson Hostler (platform-like in appearance seen heading between Wilson and Sheppard West stations on the east side of the yard) depending on the home yard. Lines 5 and 6 have a similar feature at their maintenance and storage facilities.