They were ordered by the Toronto Transit Commission (TTC) in 1992 and built in one production set between 1995 and 2001 by Bombardier Transportation in Thunder Bay, Ontario, Canada.

The T-1s had many of the same technical specifications of the H series, including the same married pair configuration, and incorporated many of the design elements that had been refined throughout the H-series program.

[citation needed] The TTC also considered upgrading the fleet to run on an automatic train control (ATC) system, which it is in the process of installing to replace the current wayside signaling system on Lines 1 and 4 and is expected to install on Line 2 by 2030 in conjunction with the opening of the Scarborough subway extension.

[6] However, due to prohibitively expensive costs of such a retrofit, it is unlikely that this will happen in the near future, and the TTC plans to replace all T-1 trains with new ATC-compatible equipment instead.

[7] In October 2022, the TTC had issued a request for proposals for new Line 2 trains similar to the Toronto Rockets, which would have replaced the T-1s.