VANCOUVER -- SkyTrain will be completely shut down starting 5 a.m. Tuesday morning as the union representing workers starts job action.

Workers will return to work on Friday at 5 a.m., said Tony Rebelo, president of CUPE 7000.

Rebelo said the union and the BC Rapid Transit Company, the company that runs SkyTrain, have been in mediated talks for four days, but "didn't really get anywhere" on the union's key issues, which include wages, staffing levels, overtime and a sick leave plan.

The SkyTrain job action comes hard on the heels of a labour dispute that nearly had Metro Vancouver bus drivers and bus maintenance workers go on a full strike. Unifor, the union for those workers, managed to strike a deal with the employer and avert a strike at the last minute. Bus and SeaBus workers voted to ratify a new three-year collective agreement on Dec. 5.

The bus drivers did a number of job actions that didn't involve fully stopping work, including not wearing uniforms and refusing overtime. But Rebelo said CUPE 7000 had determined a full work stoppage was "the safest bet for our passengers.”

"We looked at all our options right? And we didn’t want to put anyone in an unsafe situation," he told CTV News. "If an emergency were to occur, we wouldn’t have enough staff to deal with that emergency."

The job action will stop the Expo and Millennium SkyTrain lines from running, but Canada Line and West Coast Express service will not be affected.

In a statement, the BC Rapid Transit Company said it was disappointed in the union's decision, while Ben Murphy, a spokesperson for TransLink, said the three-day work stoppage is an "unacceptable escalation."

"This is an unacceptable escalation and it is going to cause an enormous amount of disruption on the expo and millennium lines on which 150,000 people rely to get to where they need to go each and every weekday," Murphy said.

The company says it is working with TransLink to put additional buses on existing bus routes, "but customers should consider alternate arrangements should a full strike proceed.”

Murphy said extra buses will not be able to fully replace SkyTrain.

In November, SkyTrain union members voted 96.8 per cent in favour of strike action. CUPE 7000 represents 900 SkyTrain workers including attendants, control operators, as well as administration and maintenance staff.

The last SkyTrain strike was a single-day shutdown over twenty years ago, according to the union. 

With files from CTV News Vancouver's Allison Hurst.