We have all encountered moving walkways in airports. I’m wondering why we haven’t seen them in other places. Perhaps the darn things are just so expensive to build and maintain. But that may change. A moving walkway is one of the options being considered in the planned $370 million Potomac Yard Metro station to be built near Amazon’s HQ2 project in Arlington County.

There are four broad design options, according to the Washington Business Journal. All but one would require a 765-foot trek to the fare gates:

• A basic ramp, with a walking time to the mezzanine of 3 minutes, 30 seconds to 6 minutes.
• A south entrance pavilion with bridge, with a walking time of 3 minutes, 20 seconds to 5 minutes, 45 seconds.
• A ramp from East Glebe Road with a moving walkway, with a walking, or not, time of 3 minutes to 5 minutes, 50 seconds.
• A south entrance pavilion with small mezzanine with a pedestrian bridge over the tracks, which would cut the distance to the station platform to 420 feet and reduce walking time to as little as 2 minutes.

Readers know me as a skeptic of extravagant infrastructure projects funded by taxpayers. Indeed, I would like to know what goes into that $370 million price tag. My gosh, what are they planning — silver-plated faucets? Corridors lined with Brazilian marble? But let’s put aside that very legitimate issue for a moment and consider the merits of a moving walkway. Would such a device be a luxury or a necessity?

If you’re investing $370 million in a Metro station, you want to make sure that people use it. You don’t want people saying is, “Meh, it takes too long to get to the station platform. It’s not worth the trouble. I’ll just drive my car and pay the parking.”

Among the many things we’ll want to know: What kind of development is planned around the Metro station? How many people will be living and working within a 1/4-mile radius of the station (the rule of thumb for how far most people will walk) and how many within a 1/2-mile radius (the outer limit for how far most people will walk). Then we’ll want to know how much walking time will a moving walkway save compared to the alternative? How many additional passengers and how much in additional fare revenue would that generate? How do those numbers compare to the additional cost of building, maintaining and, when the walkway inevitably breaks down, periodically fixing it?

It is entirely legitimate to consider moving walkways among the options to optimize the return on a $370 million Metro station investment. We should always be be open to outside-the-box thinking. But it’s also critical to subject any such proposal to return-on-investment analysis. We cannot afford gold-plated Metro stations funded at taxpayer expense… not even for Amazon.

(Hat tip: Rob Whitfield)