An estimate by the City of Winnipeg suggests most riders paid to take the bus on a day transit drivers showed their frustration with ongoing contract talks by refusing to enforce fare collection.

The City of Winnipeg estimates it lost between $40,000 and $45,000 on May 14, otherwise known as "free ride day," as a result of the job action organized by Amalgamated Transit Union 1505.

On a typical day, Winnipeg Transit makes about $145,000 in revenue. The city's estimate suggests the job action resulted in roughly 30 per cent drop in fares last Tuesday.

"The city could be saving even more money by working with the ATU towards a fair contract for our membership," Amalgamated Transit Union Local 1505 president Aleem Chaudhary said in an email statement Thursday.

Nearly 1,400 transit workers have been without a collective agreement since January. A contract offer by the city in April was struck down by 98 per cent of local ATU members.

Since last Tuesday's job action, the Amalgamated Transit Union filed a complaint with the labour board regarding alleged "retaliatory actions" against ATU members, said Chaudhary.

"Management took steps to threaten workers with discipline and potential dismissal, which when performing legal job action, is a clear violation of the Manitoba Labour Relations Act," his statement said.

A spokesperson for the City of Winnipeg said it stands by its position and looks forward to a ruling from the labour board.

"The city has been clear in its position, publicly and with filings to the Manitoba Labour Board, that the ATU's decision to instruct operators not to enforce fares on buses constituted illegal job action," the city's emailed statement reads.

The city did not elaborate on how it calculated the loss on May 14 and whether it includes typical fare evasion.

When asked whether the union would consider another free ride day, ATU spokesperson Zach Fleisher said the union is working with membership to decide its next course of action.