Rendering of a possible I-270 monorail. Image by The High Road Foundation.

Maryland will officially study a proposal to build a monorail along I-270, from Shady Grove to Frederick. Let’s examine whether that’s a crazy idea, or if monorail is a legitimate and practical possibility.

A quick refresher on the monorail proposal

In June, 2019, when the Maryland Public Works Board approved Governor Hogan’s plan to widen I-270 and the Beltway with toll lanes, the board also insisted that the state study the feasibility of building a monorail between Shady Grove and Frederick.

That request came at the behest of The High Road Foundation, a private organization that’s been developing preliminary plans for what a monorail could look like. If built, the foundation’s plan would see a 27-mile monorail, mostly along I-270, with six stops: Frederick, Urbana, Comsat (Clarksburg), Germantown, Metropolitan Grove, and Shady Grove. They say the elevated monorail would take 31 minutes to get from Frederick to Shady Grove, carry between 39,000 and 55,000 riders per day, and cost around $3.4 billion to build.

Specific strengths and weaknesses of monorail

Like any mode, monorails have specific technical merits and drawbacks. They’re neither magically perfect for every transit situation, nor a fantasy suitable only for resorts.

To understand the pros and cons of this proposal, understand what monorails can and can’t do that’s different from normal trains. The biggest difference is they’re inherently elevated, and are lighter than traditional metro trains. That makes them cheaper and more aesthetic to elevate, but with the trade-off that they must always be elevated, even if only five feet above ground.

The second biggest difference is that it’s harder — not impossible — for monorails to switch tracks. Together, these two inherent differences push monorail to be a good solution on individual corridors where most of the line is going to be elevated regardless of mode, and a questionable solution for lines that are part of a big network or have reason to run mostly on the surface or in a subway tunnel.

Most other differences aren’t inherent to the technology. Monorail proponents point to elevated rail needing less ground clearance than surface rail, but any type of train can be elevated onto piers (monorails may get by with narrower piers though, making for at least an aesthetic improvement). Proponents say monorail stations can enter buildings, but so can other trains. Proponents say monorails can be fully automated, but so can other trains.

The key difference is whether being lighter but always elevated makes a line cheaper to build via monorail than via a comparable plan using another mode. The High Road Foundation says their plan is cheaper than Metro but not bus rapid transit, which is potentially correct but shouldn’t be taken as a given, considering Miami recently discovered monorail would be more costly than heavy Metro. The foundation hasn’t compared to all other modes, such as the kind of DMU trains that are increasingly common for long-distance routes extending beyond the end of the subways and light rail. But their numbers are compelling enough to warrant a closer look.

If Frederick is the goal, do others modes get the job done?

Monorail advocates seem most keen to provide a direct transit connection between Frederick and Montgomery County. That’s an underserved transit market today, and one that likely can support better transit than it has now.

That explains why they’re not satisfied with the Corridor Cities Transitway, which if built would nicely connect walkable communities in Gaithersburg and Germantown, but wouldn’t help longer-distance trips from Frederick.

It also explains why they’re not satisfied with MARC’s Frederick spur, which aside from its extremely limited schedule has to travel far outside its way inbetween Frederick and Germantown. Adding 50 trains a day to the existing MARC spur would still result in a long, slow, indirect trip.

MARC map showing the existing Frederick spur, and the more direct potential I-270 route (in pink). Original image by Maryland, modified by the author.

So, assuming a more direct connection between Frederick and Shady Grove is desirable, is monorail the only or best way serve it? Let’s look at other possibilities.

Bus rapid transit

If Maryland goes ahead and builds its I-270 express toll lanes all the way to Frederick, by far the cheapest transit option would be to run buses in the toll lanes. Toll lanes allow cars and can get congested, but in theory the toll amount changes to keep the lanes flowing, meaning toll lanes can be almost as good as a busway, depending on the service. Buses would have the added benefit of being able to continue on to downtown DC, Tysons, or anywhere else, without forcing a transfer to Metro.

Virginia runs buses on its toll lanes, but often only at peak times, and sans the kind of rapid busway stations that keep buses moving quickly. To actually be as good as a monorail (or any train), buses on I-270 would need frequent all-day service, and busway stations either “in-line” with the highway or along easy to reach, fast busways slightly off the highway. Making buses exit to take long, slow, winding, routes through surface streets to reach stations won’t cut it.

An "in-line" highway BRT stop in Minneapolis. Image by MSPdude used with permission.

Stations like that would, of course, increase the cost. But BRT on the toll lanes would still be vastly cheaper than any other rapid transit solution, because 90% of its runningway would be provided by the toll project. That’s if the toll lanes are built. If they’re not built, BRT would have to construct its own runningway, and thus rail might be more cost competitive.

Metro rail, light rail, DMU

Metrorail is a non-starter to go all the way to Frederick. It’s too expensive, and extending it to Frederick would cause operational headaches all the way to Metro Center and Glenmont. Maybe someday Metro will extend deeper into the suburbs, but not that deeply anytime soon.

Light rail is an option, with the benefit that it could be elevated where necessary but at-grade where that’s cheaper. It’s believable that a transit line parallel to I-270 in Gaithersburg and Germantown might need to be mostly elevated, especially if it snakes back and forth between the highway and stations a quarter mile off the highway, as plans call for. But north of Germantown there’s plenty of room to save money by running on the surface. The monorail-booster High Road Foundation says monorail is less expensive than even surface light rail, which may or may not be true.

However, light rail is a generally slow mode, more suitable for shorter lines with frequent stops than for long, commuter-rail like routes. Like monorail it would require a forced transfer at Shady Grove. It’s probably slower than monorail would be, all other things being equal. And regardless of how light rail costs compare to monorail costs, light rail wouldn’t be the cheapest type of train.

DMU trains — Diesel Multiple Units — are a hybrid between commuter rail and light rail. They’re as light as light rail, and can run anywhere light rail can run, including elevated or even on-street. But they’re more suited to longer routes, with slower acceleration but faster top speeds, and are cheaper to construct due to not having overhead electric wires.

eBART, a DMU 40 miles outside San Francisco that extends from the end of the normal BART line. Image by Jim Maurer licensed under Creative Commons.

DMUs can also run on existing freight tracks, adding a level of flexibility that even light rail doesn’t have. A new DMU line could theoretically be built from Frederick to Metropolitan Grove in Gaithersburg, then join the MARC tracks and continue all the way to Union Station or Crystal City. It wouldn’t have to force a transfer at Shady Grove, wouldn’t contribute to Metro’s core capacity problem, and might potentially be cheaper than monorail.

There’s a reason DMU is so often the mode of choice for new rail lines in places like Frederick, where it’s too far for light rail but needs something better than commuter rail. Without detailed studies, no one can say definitively that DMU along I-270 would be cheaper or better than monorail, but DMU would be the conventional choice.

Include monorail in a real Alternatives Analysis

Providing a better transit connection to Frederick is a laudable goal. The need is there. And monorail could legitimately turn out to be the best method for doing so. Monorails are a workable technology, and the specifics of the I-270 corridor are close enough to suitable for them that it’s plausible monorail might be a sensible choice, especially if The High Road’s cost projections are accurate. Transit supporters should be open to the possibility that monorail is worth studying.

But the hopes of monorail advocates should not be taken as gospel by state planners when comparing it to other possibilities. Cost estimates and technical projections from organizations with clear modal agendas have a tendency to be overly rosy towards their preferred mode. An objective look might find what they say is true, or it might find that other possibilities are more practical. And other possibilities that are likely if not surely to be as good or better than monorail do absolutely abound.

That’s the reason this monorail effort elicits groans from transit experts. Monorail could work, but there’s no good reason to assume out the gate that it’s the only or best transit solution for I-270. The message that assumption sends is that leaders are more interested in looking cool than in making wise decisions.

That concern rings especially harshly for a governor who seems to revel in slashing transit and in canceling long-planned transit projects, only to make headlines studying splashy but half-baked ones that are unlikely to be built. Governor Larry Hogan canceled the fully planned and funded and good Baltimore Red Line subway, cut back MARC plans to expand train frequency, and effectively ended work on the Corridor Cities Transitway and Southern Maryland light rail.

To fail on those projects, but to chase monorail and maglev and hyperloop, all under the auspices of being an efficient steward of the public trust, suggests the governor is more interested in chasing after shiny objects than in serious transportation planning, regardless of the actual merits of a monorail along I-270. That’s concerning no matter what makes the most sense for I-270, and casts shadow on the state’s ability or willingness to plan transit in good faith.

Which is a shame, because transit to Frederick deserves a professional Alternatives Analysis that includes a serious look at, yes, monorail, but also DMU, BRT, and other modes. Maryland should do that, and monorail should be included as a serious alternative. But such a study should set out primarily to answer the question of how to best reach Frederick, not whether monorail can replace the HOT lanes, or whether monorail will do everything The High Road Foundation says it will do.