TTC boss Andy Byford said Tuesday that an "archaic" communication system was a factor in Monday's difficult commute in which a handful of problems caused thousands of transit users to arrive late for work.

In a candid interview with Metro Morning host Matt Galloway, Byford said the TTC uses a text-based system more than 40 years old to stay in touch with streetcar and bus operators.

"It is a system that was state-of-the art in the 1970s, but is now completely obsolescent," said Byford.

"It's basically a text system that you can send text messages to 10 vehicles at a time. You have to wait for them to acknowledge before you can then communicate with the other vehicles. So quite often, ridiculously, the bus and streetcar operators don't know what's going on."

And while the communication system didn't cause Monday's troublesome commute, it did delay getting updated information to operators and passengers. The delays prompted Byford to issue an apology on Monday. He made similar apologies after difficult commutes on weekdays July and March.

Monday's problems included:

A water main break at Yonge and Lawrence caused water to "cascade" onto the platform at Lawrence subway station. This wasn't the TTC's fault but for the entire morning commute, trains rolled through the station but passengers couldn't board or get off there. Instead, the TTC had to operate shuttle buses.

Streetcar derailment, at Russell yard near Greenwood Avenue, possibly caused by ice in the switches, blocked vehicles in the yard, leading to delays on the 510 Spadina route.

A streetcar broke down at at Queen Street and Broadview Avenue, causing delays of up to 90 minutes on both the 501 Queen and 504 King streetcar routes.

A collision involving a streetcar and a vehicle at Dundas and McCaul streets caused more delays.

Subway delays on Bloor-Danforth line.

"I felt I owed people an explanation," said Byford of Monday's commute. "I know it was a very frustrating trip for them."

Byford said the TTC has much work to do when it comes to communicating with passengers when service is interrupted. Some so-called e-alerts failed on Monday and messages sent to subway platform screens aren't seen by many commuters.

Byford said updating the communication system is a priority and he's pushing to have the money added to the TTC's budget

Another problem Byford mentioned is the difficulty getting new parts for old streetcars. Some need to be fashioned by a blacksmith. Ongoing struggles with an outdated signalling system and track in need of replacement are also problems, Byford said.

However Byford also said problematic commutes overshadow positive moves underway to modernize the TTC. He pointed to articulated buses, bigger streetcars and the Presto fare system as examples of upgrades in the works.

"Most days we get it right," Byford said. "Most days most people get to work without incident."