BART employee unions are coming up on another expiration of their four-year contracts on July 1, and like they did in 2009 and 2005, they are again threatening to strike. But is the current strike threat just about salaries and benefits, or is it about safety issues? There are competing tales.

Negotiations have been ongoing since April, and a mediator is coming in this week to try to speed things up.

A spokesperson for Service Employees International Union Local 1021 says that the negotiations center on safety issues, in particular lighting in tunnels that could threaten the safety of both workers and passengers in the case of an emergency evacuation. But a spokesperson for BART says that's not primarily what's being discussed by the unions internally, who are, as always, more concerned about salaries, work rules, and benefits — and about how much employees will have to pay into their own health care or pensions.

Both Local 1021, which represents 1,430 service and clerical employees, and Amalgamated Transit Union Local 1555, which represents 945 train operators, are holding strike authorization talks Tuesday. BART seems to think, however, that this is all just posturing over the pensions and benefits question. BART management has said they need to control benefit costs going forward if they are going to be able to afford rail improvements and new rail cars as planned over the coming decades.

Antonette Bryant, president of Local 1555, earlier said the union "would sign a contract today if it keeps up with the cost of living in the Bay Area and gives us health and safety protections. We don't want to go on strike."

Some of you may recall the crippling BART strike of 1997, which lasted six days, caused massive traffic jams, and created no shortage of ill feeling toward BART and its employees in the mainstream media. BART employees, meanwhile, ended up winning the wage settlement they sought, and have not gone on strike since. The BART system saw about 275,000 rides a day in 1997, and that number is now up to about 400,000.

Threats of strikes came up in 2005 and 2009, but strikes were averted in last-minute negotiations.