A backup computer system that could run the SkyTrain in the event of breakdown would cost $20 million, according to the TransLink executive in charge of rapid transit.

Fred Cummings told CTV News on Friday that his company has begun an investigation into the computer failure that shut down the Expo and Millennium lines during rush hour on Thursday. Part of that investigation will be to determine if a backup system should be purchased.

Cummings is the president and general manager of B.C. Rapid Transit Company, which operates the SkyTrain on behalf of TransLink. On Thursday, he apologized to to the public for the shutdown, which caused massive delays in the afternoon commute and left some people stranded in trains between stations.

“We disappointed a large number of loyal customers,” Cummings said. “I don’t think anything I can say right now is going to make a lot of people happy. I’m getting a lot of comments on Twitter and I’m reading them all. I’m seeing them. I understand the anger that people feel.”

Cummings told CTV News that a card in the SkyTrain system’s main communications computer failed, leaving every train on the Expo and Millennium lines stranded where it was. He said the card in question had never failed before, so Thursday’s problem “came up out of the blue.”

“It’s a system that’s not that old,” Cummings said. “It was installed as part of the Millennium Line extension and we expect a lot longer life out of one of these cards than 12 or 13 years.”

The SkyTrain started running again between downtown and Metrotown Station first, before the rest of the system came back online. While they were stranded between stations, passengers on some trains forced open the doors. Others got out and started walking along the tracks, which Cummings said ended up prolonging the shutdown.

“As soon as we got word that people were breaking out of the trains, we had to de-energize the system,” he said.

TransLink released a statement on Friday reminding passengers never to exit SkyTrain cars between stations unless authorized or escorted by TransLink staff.

“The tracks are electrically charged with 600 volts, as indicated by warnings and diagrams throughout our SkyTrain system,” the statement reads. “A passenger may suffer serious shock, injury or death by stepping onto the track.”

Transit Police intercepted the passengers who forced their way out of stalled trains on Thursday. Doing so is illegal and can lead to criminal mischief charges.

The problem began at approximately 5 p.m. and shut down the entire system for roughly 45 minutes, but service did not completely resume until 10:30 p.m. The shutdown caused ripple effects throughout the region’s transit system, with long waits for crowded busses at many stations.

By Friday morning, however, there was no sign of the chaos of the previous day. Most of the SkyTrain riders CTV News spoke to were just happy that the trains were running again and they were able to get to work on time.