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.

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.

The three unions representing some of the city's most essential workers are all considering the same action: a strike.