The Trois-Rivières & Shawnigan Street Railway was a radial running from Trois-Rivières up into the Laurentides, via Shawnigan & Grand Mère. It fell into the LT&L’s orbit in 1907, soon after electrifying – at 1200 VDC – from Trois-Rivières to Grand Mère, and operated as an independent railway until immediately after the second world war, when the LT&L officially merged it into the system.
In the mid 1950s, after passenger traffic almost completely dried up (there were still mixed trains running up to the end of the line at Saint-Roch-de-Mékinac, but the regular interurban traffic down to Trois-Rivières completely evaporated under the pressure of automobiles on improved roads) the LT&L considered pulling down the wires, but was convinced by the PV&T to hold off on that during the merger talks that were just starting up at that time.
In 1966, the LT&L electrified their mainline from Montréal to Québec, and as part of that project updated the (unused for freight since 1958) tension on the railway to 3000 VDC and replaced the class DL2 locomotives that had been hauling freight on the line.
There is still quite a bit of freight traffic between Trois-Rivières and Saint-Roch-de-Mèkinac, but the mixed trains north of Grand-Mère evaporated in the 1980s, leaving only seasonal tourist trains along the line.
Several of the TR&S'a passenger & combine motors survived into the 2020s as MOW cars for the LT&L. The illustrated one – built by Ottawa Car is 1930 – was restored in 1989 (and again in 2020 after sitting outside for a decade!) and is currently used for fan trips on ORRC rails (there are only a couple of Parsons Vale properties that use trolley poles instead of pantographs, and the ORRC system is by far the largest of them)