Amazon HQ2’s arrival in Crystal City, Virginia, in the inner suburbs of Washington, DC, is going to be paired with some useful investments in transportation infrastructure in the immediate vicinity of the new office complex.

But while the ideas currently on the table are sound (adding an exit to a metro station, a pedestrian bridge to another, etc.), the region really ought to think bigger.

Washington, Baltimore, and northern Virginia have the bones in place to stitch together two existing commuter rail systems and create what could be America’s first high-quality regional rail mass transit network — an analogue of the RER (Réseau Express Régional) in the Paris area or the S-Bahns in Berlin, Munich, Zurich, and other German-speaking cities.

Right now MARC trains take Maryland passengers into Washington’s Union Station from one side of the city while Virginia’s VRE trains arrive from another. Then they stop. Instead, the systems should merge, allowing trains to run in both directions all day — passing through the center of the city and giving Maryland residents direct access to Virginia job centers while giving Virginia residents the ability to reach BWI Airport and even the City of Baltimore.

Amazon wouldn’t be the reason to do this, though the transformation to regional rail would make the existing VRE commuter rail station at Crystal City, the stop near the new Amazon center, more useful to Amazon workers.

Rather, Amazon’s arrival could and should be the occasion to step back and think about the fact that a radical improvement in the region’s transportation capabilities is possible. And you could make it happen in exchange for a relatively small amount of money in the grand scheme of things if regional leaders are willing to work together for a change and break some taboos.

Regional rail versus commuter rail

David Alpert, the founder of the advocacy group Greater Greater Washington, calls a version of this plan the Metro Express, but I think that sells it short. What the region ought to do is combine and upgrade the existing MARC (Maryland Area Regional Commuter) and VRE (Virginia Railway Express) commuter rail services into a unified system. I’d like to call it the Chesapeake Bay Regional Rail to acknowledge that it’s not just a supplement for Washington Metropolitan Area Transit Authority (WMATA)’s existing Metro service but a bold vision to improve connectivity across a broad region.

The details of what the transformation would require are important, but to understand them it’s important to understand the broad difference between commuter rail (as it’s understood in the United States) and regional rail, as seen in an RER or S-Bahn system.

These concepts are similar in that they both involve using mainline railroad tracks (the same ones that CSX freight trains or Amtrak intercity trains run on in the United States) to provide an urban transportation service aimed at a customer base that is assumed to be primarily sleeping in their own beds at home. But the differences are enormous.

Fares: Riding regional rail from New Carrolton to Crystal City should cost exactly what it would cost to ride DC’s Metro from New Carrolton to Crystal City. A trip that’s longer than any Metro trip (like Alexandria to BWI) could cost more, but the cost should be proportionate to the distance. Currently, commuter rail fares are much higher than Metro fares.

No conductors: To make the fares cheaper, you need to reduce operating costs. That means that instead of employing conductors to walk every train checking tickets, you need to either install fare gates (like on Metro) or more plausibly use sporadic spot inspections and a proof-of-payment system.

More frequent trains: Conductors obviously won’t be happy about losing their jobs, but the good news is that with trains cheaper to operate you can run more trains — meaning conductors can get new jobs driving the trains. And, of course, we’ll also need some ticket inspectors.

Electric multiple units: DC-area commuter rail is currently driven by diesel-powered locomotives. That’s okay for a start, but ideally we should move to electric multiple units (again, like Metro), where you draw power from an overhead catenary and each car propels its own wheels. This is cleaner; reduces operating costs (crucial to keeping fares down); and critically lets the trains accelerate faster, which greatly increases speed (and therefore frequency of service) on a system where the trains stop relatively frequently.

Level boarding: Right now, MARC stations have high platforms that let you step straight into the train car (again, like on Metro), but VRE stations have low platforms and you need to climb stairs to get in. Level boarding is much faster — and much better for accessibility — so upgrading VRE stations to MARC standards is a must.

All-purpose transit: Commuter typically aims to serve peak hour commuters who are expected to mostly drive to station-adjacent parking lots. The basic idea is that you are trying to de-congest highways at their most crowded time by diverting drivers onto trains with the promise of cheaper parking. Regional rail is an all-purpose transportation service that runs both directions throughout the day (including on weekends).

Transit-oriented development: Regional rail stations should be surrounded by apartment buildings, not parking lots. And the buildings should contain the ground-floor retail amenities (supermarket, pharmacy, bank, coffee shop, restaurants, gym, bar, yoga studio, hardware store) that let you get through daily life largely on foot.

These are big changes, and they would cost some money to implement. You’d need to upgrade stations, and it might be necessary to add extra tracks to the Long Bridge that connects DC to Arlington, Virginia, to accommodate the extra traffic. Electrification of tracks on this scale, in particular, involves a significant up-front outlay of funds even though it saves money in the long run.

That being said, the key advantage of this model of regional rail is that it’s a lot cheaper than building new highways or rail lines from scratch. The most expensive parts are already done.

The benefits of regional rail

Narrowly speaking, increasing the speed and frequency of VRE while allowing MARC trains to run through Union Station into Virginia would allow the region to accommodate a large increase in Crystal City jobs without a crushing increase in traffic.

But the benefits would be significantly broader: Baltimore’s large stock of relatively affordable housing would become significantly better-connected to employment opportunities, for example, and a much larger group of people would gain transit access to BWI Airport.

A cheaper, faster, and more frequent version of the existing Brunswick Line on the MTA (Maryland Transit Authority) would connect disparate parts of Montgomery County, Maryland, to each other. Residents of Silver Spring, Maryland, and other inner suburbs would gain an express ride to downtown and northern Virginia job centers, reducing crowding on the DC Metro’s currently overtaxed Red Line. Adding an infill stop at Ivy City could address one of DC’s most notably transit deserts.

There are a bunch of fussy technical impediments to getting this done, and it would all cost money. But the cost-benefit analysis is extraordinarily favorable compared to other large-scale transportation projects, simply because the biggest fixed cost of all — building the train tracks — is already done.

The real challenge isn’t monetary but organizational. On net, a regional rail organization would employ more people rather than fewer. But conductors would lose jobs and need to retrain and possibly join a different labor union. Schedules would need to be coordinated with Amtrak and CSX. Union Station in DC would need to reorganize its station. Two discrete bureaucracies would need to be merged into one.

And most of all, decisions would have to be made about who pays for a series of projects that would cross jurisdictional boundaries in complicated ways.

Regional leaders, in other words, would need to show some leadership.