Thousands of Philadelphia city workers are preparing to walk off the job, if a new contract isn't reached. More than 9,000 employees, who work in prisons, sanitation and 911 dispatch, realize a strike would create a major impact.

This does not mean the union is on strike; it means leaders can call a strike at any time if they can't reach a deal in contract negotiations with the city. It's not clear when a

PHILADELPHIA (WPVI) -- Philadelphia's largest city workers union has voted to authorize a strike. The results announced Thursday showed 87% of workers voted in favor of the strike authorization. This does not mean workers are hitting the picket line, however.

Philadelphia's largest municipal employee union, District Council 33, has voted to authorize a strike against the city.

Bus, trolley, and transit operators in the city are currently working without a contract. The last contract expired at midnight on Thursday, but union workers held off on a strike as both sides decided to continue negotiations. Meanwhile, on Friday, the union representing suburban transit workers formally voted to authorize a work stoppage.

The union that represents thousands of Philadelphia mass transit system workers has agreed to delay a potential strike, saying progress was being made in ongoing contract talks.

A union representing thousands of city employees, including sanitation workers, has voted to authorize a strike. This doesn't mean they're on strike yet but it allows union leadership to call one if necessary at any time.