SEPTA workers might strike soon. It wouldn’t be the first time.

» READ MORE: Update: SEPTA strike averted as TWU 234 reaches tentative deal

Members of the Transport Workers Union Local 234 on Sunday, Oct. 1 authorized a strike if union and SEPTA negotiators can’t reach agreement before the current contract runs out at 11:59 p.m. on Oct. 31. Local 234 leaders say they’re prioritizing public safety in the talks, demanding that SEPTA do more to protect its members and the public from crime and disorder on the system, including with more policing.

The transit authority is also in contract talks with three other unions: the Fraternal Order of Transit Police, Lodge 109; the Brotherhood of Locomotive Engineers and Trainmen, Division 71, which represents Regional Rail engineers; and the union that represents conductors on the commuter-rail system, Local 61 of the International Sheet Metal, Air, Rail and Transportation Union (SMART).

Here is what happened in previous SEPTA strikes:

TWU Local 234 walked off the job for six days; the biggest issue was retirement benefits. SEPTA’s contributions toward union members’ pensions did not rise in tandem with wages when workers made more than $50,000. Managers’ pension benefits were not capped. The union also wanted to reduce out-of-pocket health-care costs and win longer breaks for bus, trolley, and subway operators between shifts and route changes.

SEPTA and the union reached an agreement Nov. 7, the day before the general election. Democrat Hillary Clinton’s presidential campaign was worried about voter turnout, and the city sought an injunction to end the strike. It proved unnecessary.

» READ MORE: SEPTA deal, reached at 5 a.m., will raise wages and health contributions (from November 2016)

Talk about leverage. TWU was ready to strike just before the first home game of the World Series between the Phillies and the New York Yankees. Gov. Ed Rendell pushed the two sides to continue talking, and the transit workers waited to walk out until three hours after the end of Game 5, the last in the series played at Citizens Bank Park.

It was a bitter strike, coming just a year after the stock market’s meltdown started the Great Recession. Local 234 President Willie Brown called himself “the most hated man” in Philadelphia. Mayor Michael Nutter was harshly critical. Brown called him “Little Caesar.”

The strike was settled Nov. 7 with a deal on a five-year contract. Transit workers got a $1,250 bonus, a 2.5% raise in the second year, a graduated increase in SEPTA pension contributions from 2% to 3.5%, and the maximum pension benefit was raised to $30,000 from $27,000.

» READ MORE: Strike ends; SEPTA, union sign deal (from November 2009)

Two unions walked off the job on Halloween, halting most bus, subway, and trolley service in Philadelphia and its Pennsylvania suburbs.

Negotiations collapsed mostly over SEPTA’s insistence that workers pay 5% of medical insurance premiums. At that point, the authority paid 100% of the workers’ premiums for family coverage.

In the end, it was solved by Gov. Rendell, a Democrat who had been Philadelphia mayor in the 1990s. He agreed to give promised state money to SEPTA early, so it could pay premiums in advance, reducing its costs.

In the resulting four-year deal, the unions had to pay for 1% of their medical premiums. They also received 3% yearly raises.

City transit workers’ contract expired in March, but they did not strike until June — and then stayed out for 40 days. The two sides reached an agreement in July, but it fell apart. TWU members had returned to their jobs and kept working under an extension of their old contract. A final agreement was signed Oct. 23.

The union agreed to SEPTA’s demand that injured-on-duty benefits be limited. The old contract gave them full pay and benefits while on leave after a work injury. SEPTA wanted to hire an unlimited number of part-time workers. The union agreed to 100 part-timers to drive small buses.

SEPTA’s chief negotiator was David L. Cohen, famous for reining in unions representing city workers during Philadelphia’s bankruptcy in 1992, as Rendell’s mayoral chief of staff. Now, Cohen is President Joe Biden’s pick to be U.S. ambassador to Canada.

» READ MORE: What you need to know about a possible SEPTA strike next week

A two-week strike stilled city buses, trolleys and subways until an agreement was reached April 10. Transit workers would get 3% raises per year over the three-year span of the new contract, as well as increases in pension benefits and sick pay.

The union agreed to several cost-reduction measures, including a restructuring of SEPTA’s workers compensation policies.

Mayor Ed Rendell, a villain to many in labor for winning givebacks from city unions in 1992, pushed SEPTA to offer more generous terms to TWU than it had initially. Cohen, who was his chief of staff, crunched the numbers to make it work. Three years later, out of the city administration and working as a lawyer, he was hired as SEPTA’s chief negotiator.

When TWU struck the city transit division in March 1986 over a variety of economic issues and work rules, some bus drivers pulled over mid-route and told passengers to dismount, The Philadelphia Inquirer reported.

Members were particularly incensed at what they considered SEPTA’s draconian disciplinary procedures. Union leaders said the issue was a basic lack of respect. The strike was settled in four days.

Drivers for 23 suburban bus routes, two trolley lines in Delaware County and the Norristown High-Speed Line — all members of the United Transportation Union — struck for just over two months, affecting about 30,000 passengers a day.

Employees in what was then known as SEPTA’s Red Arrow Division — after the private transit company that used to own the routes and lines — made considerably less than their city counterparts and had weaker pension benefits. They won raises and pension changes that brought them closer to parity.

Thirteen separate unions walked off the job on the commuter rail lines that SEPTA had taken over at the beginning of the year from Conrail, successor to the bankrupt Pennsylvania and Reading Railroads.

In addition to wages, a key issue was SEPTA’s demand that union train conductors accept pay cuts. The authority had already cut the number of those workers by more than half.

Eventually SEPTA reached deals with a dozen of the unions. The 13th local, which represented 44 railroad signalmen, held out longer. Main issue: Whether SEPTA had the right to contract with outside firms for some types of signal work.

The Regional Rail strike remains SEPTA’s longest work stoppage since 1975.

» READ MORE: SEPTA transit workers vote to authorize a strike if needed

About 36 suburban bus drivers and mechanics operating routes primarily in Montgomery County, and some routes in Bucks, won an 8.5% wage increase over three years.

The bus routes were the descendants of the Schuylkill Valley Lines and the Trenton-Philadelphia Coach Lines, which SEPTA acquired in 1976 and 1983, respectively. Service has grown, and the collection of bus routes is known as the Frontier Division today.

Transit workers shut down buses, trolleys and subways in the city on March 15, seeking job security in the form of a no-layoff clause, wage increases and a bar on SEPTA hiring part-time workers.

And the Red Arrow division went out for 46 days seeking higher wages and better medical benefits. SEPTA also backed down a demand for permission to hire private contractors for some work on the suburban buses, trolleys, and the Norristown High Speed Line.

After a bitter strike, union members who run the city transit division got higher wages and more benefits, after rejecting an arbitrator’s proposed contract that was portrayed in news reports as generous.

A furious Mayor Frank Rizzo told reporters the strike “can last 10 years for all I care.” He said of the union’s rejection of the earlier offer: “It is outrageous, and I hope the people won’t forget it.”

Transit workers, concerned about the ravages of inflation, wanted a clause giving them cost-of-living increases and enhancements to health-care benefits. Those were granted after Rizzo agreed to add $7.5 million to the city’s annual SEPTA contribution. Perhaps that’s one reason the mayor was so annoyed two years later.

This story has been updated to add details of the 1995 strike.