SEPTA  is publicizing contingency plans in case of an employee walkout.

SEPTA (Southeastern Pennsylvania Transit Authority) trains at Philadelphia's Frankford terminal (William Thomas Cain/Getty Images)

Its contract with transportation workers expires at 12:01 a.m. Saturday.

Officials with the Southeastern Pennsylvania Transportation Authority officials said Friday that they've asked the union for a three-month contract extension, but received no response.

A spokesman for Transport Workers Union Local 234 could not immediately be reached for comment. The union represents about 4,700 employees.

SEPTA says there's been no indication a work stoppage is planned.

Officials say regional rail lines that serve the suburbs would continue operating during a walkout. Extra cars would be added and managers would help collect fares.

However, city transit lines including buses, trolleys and subways would not operate.

A 2009 strike by transit workers lasted six days.

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