D.C.’s Metro is in a death spiral. Revenue and ridership are down. Delays, accidents and, yes, fires greet beleaguered commuters and unsuspecting tourists frequently, slowing and derailing urban travel around the nation’s capital.

So, of course, the Amalgamated Transit Union Local 689, the largest employee union representing Washington Metropolitan Area Transit Authority workers, voted to strike. To pressure management to cave to its demands for more money, cushier working conditions and an even better contract, the union is threatening bring the nation’s capital to a halt.

That action is an affront to riders who rely on the system and the taxpayers who subsidize Metro’s shoddy service and inept and overpaid workforce.

Before WMATA’s unions can bully and blackmail Washingtonians anymore, Congress should strike first and abolish all five of Metro’s unions.

Without Metro’s unions, area taxpayers and commuters can breathe more easily and might eventually get the world-class transportation they deserve and already pay for.

The partnership between the federal government, Maryland, Virginia and the District of Columbia was created by an act of Congress in 1967, with shared governance and pooled resources contributing to an integrated transportation and infrastructure system once billed as a model for the future.

Today’s dilapidated system is a shadow of its former self. Ridership is down to pre-2000 levels despite the region’s population growing by 30 percent. With crowded roads and more economic activity, Metro’s demand should be up, but it is rarely the choice of discerning commuters who want to arrive unharmed and on time at their destination.

The death spiral of rising fares and reduced service and reliability further drives away customers, which increases the amount that taxpayers or remaining riders must bear. WMATA is easily the most expensive major city transportation (rail and bus) system in the country, costing $4.03 per rail mile and $4.63 per bus mile to operate per passenger.

But if you hadn’t noticed, despite ever rising passenger fares, that is not how much a Metro ride costs. Area governments and the feds pay 77 percent of the $3.2 billion annual operating cost of WMATA, making Metro a money pit for taxpayers.

Now WMATA’s leadership wants more — an additional $25 billion over the next decade to be exact. But that eye-popping sum rightly embarrasses Metro’s General Manager Paul J. Wiedefeld, who insists the system can squeak by with an infusion of $15.5 billion in “dedicated” funding, raised through new taxes used to exclusively subsidize Metro.

But new taxes, including the ride-hailing taxes the D.C.  Council just imposed on Uber and Lyft, merely paper over the structural financing and spending issues afflicting WMATA.

The elephant in the room is that employee pay and benefits comprise 71 percent of Metro’s operating budget, and that doesn’t even account for the $2.8 billion in unfunded liabilities for union employees’ retirement and health care.

According to WMATA’s own data released to the D.C. Council, the average salary and fringe benefits (pension plus health care) compensation for a Metro employee exceeds $109,000, which is $20,000 in total compensation more than the average worker in the D.C. area. The gap is even wider when you compare WMATA employees in similar occupational fields around the District. Here, private-sector bus drivers earn only (in pay and benefits) $59,000 on average, while Metrobus drivers earn almost twice that.

One of the chief reasons is excessive and often abused overtime compensation, which cost WMATA more than $83 million in fiscal 2017. That averages to more than $7,800 per overtime-eligible employee. Even more peculiarly, WMATA employees accrue pension benefits relative to their overall pay (including overtime) — not just their base pay — a practice that is severely out of line with common private and public-sector labor rules.

Furthermore, most of the $300 million in “services” costs are really personnel costs related to hiring outside contractors to do the some of the same work WMATA’s own union employees are supposed to be doing.

But that really started two weeks ago when a mass action by bus drivers arriving late to work snarled the commutes of bus riders, who are disproportionately poor, disabled and work in jobs that require punctuality.

Ironically, WMATA’s founding document, the compact, prohibits union strikes altogether, instead forcing management and the unions into binding arbitration.

But the unions like it fine that way because federal arbitration almost universally results in the adoption of the union’s demands. The last negotiation ended with the mediator giving a 3 percent automatic annual pay raise to employees plus a 3 percent cost-of-living adjustment and maintaining all union work rules, benefits and perks.

Even common-sense reforms by management, such as employee background checks or the ability to fire lying safety inspectors, are blocked in litigation by the union.

The unions’ chief functions are to facilitate overly generous payments to un-fireable incompetents and nepotism cases who do little work and endanger their charges’ lives.

If Congress does not act swiftly to revise the compact, abolish the collective bargaining rights of WMATA’s employees and sanction the unions if they do strike, Washingtonians will pay a steep price in higher taxes and a deficit in quality transportation.

Placating Metro’s unions will only accelerate the silent boycott by potential riders, leaving only those with no other options to risk their lives on the roads and the rails.

Sean Kennedy is a visiting fellow at the Maryland Public Policy Institute, a nonpartisan thinktank based in Rockville.