As the TTC awaits more new streetcars from Bombardier, the current fleet is struggling to handle the load given the unreliable state of the CLRV and ALRV models, some of which are pushing 40 years old. 

That means big changes are in store for some commuters. Starting on February 19, streetcar service on both the 505 Dundas and 506 Carlton routes will be replaced with buses. According to the TTC, these replacements will be in place "until at least 2019."

Unfortunately due to the cold weather and other factors, we have a streetcar shortage. Because of this the 505 and 506 are being replaced with buses during large portions of the day. There have been no route changes, but this change can cause unpredictability. Sorry.^RA🚀

— TTC Customer Service (@TTChelps) January 3, 2018

For the TTC, it's all about fleet management. By using buses on these routes, "those legacy cars that remain reliable and roadworthy [will]
be available for service on routes, like King Street, where demand is critical."

Commuters on these routes have already received a sneak peek at the changes courtesy of the extreme cold weather Toronto's experienced this winter, which decimated the old cars and forced buses into service on Dundas and Carlton already. 

 As they arrive, new streetcars are being added to King St., but at the rate Bombardier's going, it might take well beyond the start of next year to see the return of regular rail service on the 505 and 506 routes.