The original system was Bus Rapid Transit (BRT). Buses would operate down dedicated roadways, known collectively as the Transitway, and stopping at large Bus Stations, typically located at popular destinations, which also allowed a transfer to local and other bus routes.

On high frequency and major cross city routes, typically the routes 95 and 97, 60 foot long articulated (accordion) buses were used. They allowed for a high passenger capacity and offered easier boarding due to 3 sets of doors, that would all open at each station stop.

The Transitway passed through the downtown core, along Albert Street (heading Westbound) and Slater Street (heading Eastbound). At peak periods of the weekday, buses had to pass through approximately a dozen traffic lights, as well as board and disembark passengers at the main stops. It was common to see a lineup of buses for several blocks or more as one stopped bus boarding passengers or one red light would halt the entire flow. The LRT solved this by creating the downtown tunnel, to pass the trains underneath the street, thereby solving this bottleneck, by providing a dedicated right of way, free of traffic lights or stopped vehicles.

The LRT first opened in October 15, 2001 with the Trillium Line.

There were 5 stations on the initial LRT network. They are found on the Trillium Line and are Bayview, Carling, Carleton, Confederation (later renamed to Mooney's Bay) and Greenboro.

The time to construct the initial Trillium Line is difficult to determine as it was initially a pilot project, almost entirely using already existing Canadian Pacific Railway track. The only work required was building the actual stations and the passing tracks at Carleton Station. The initial Confederation Line construction began in 2013 and was completed in 2018.

The Trillium Line was built at a cost of $21 million, due to the use of the already existing Canadian Pacific Railway tracks. The Confederation Line was built at a cost of $2.1 billion.