In order to get charged the correct fare, TransLink's new system requires users to tap in when they board a bus and tap out when they leave.
Each tap only takes two seconds, but Unifor local 111 vice-president Gavin Davies worries those seconds multiplied by all the users and all the stops will cause system-wide delays.
"You could have anywhere between 30 and 60 passengers tapping off,” he said.
“You multiply by all the stops along the route, on the conservative side we could be seeing anywhere from 10 to 15 minutes additional running time needed."
Davies wants TransLink to add more buses to pick up the slack.
“We're already taxed as far as transit operators in getting from point A to point B in the regularly scheduled time,” he said.
“Buses are constantly running late and that's only going to be exasperated by now additional time needed to allow passengers to ensure that when they've tapped off, they've been dinged for the appropriate travel distance.”
TransLink has yet to comment on this issue, but officials have said they're welcoming lessons from the ongoing testing phase.
"We really want to make sure we take into account any of the issues that may crop up,” said spokesperson Michael Madill.
The Compass cards are scheduled to roll out across the transit system next year.