Moving Walkways as Mass Transit

There has been a bug in my bonnet for a long time. A project that has lived in my brain rent free for at least six years (documented) and has been a fleeting thought for many years before that time. In many ways, this vision I’ve had is even more extreme and upending for most humans than the concept of sending humans to Mars.

I love driving my car and the freedom. But I hate the colossal waste of resources associated with individual car travel, so I’m a huge advocate of mass transit. The problem is that traditional forms of mass transit fall into a number of traps that either make car usage more economical, convenient, or efficient in many cases. I think there is the potential of flipping the script where not only is there little advantage to using a car, but mass transit is much more enjoyable for most of the population (individual transport will always have a place).

So this blog post is very much a plug/introduction for my idea. I’m hoping to generate enough interest that I get some constructive comments on the concepts that allow me to move the needle on revolutionizing mass transit. If you’ve made it this far, hopefully you’ll stay for the rest of the ride. I’ll try to make this initial foray brief….

The Problem

I’ve covered the problem in a prior blog post, Urban Mass Transit. In that blog I cover what I consider attributes of “good” mass transit and compare the advantages and disadvantages of two high level examples, a subway system and a bus network. In the end, my theory is that mass transit has not been well embraced primarily because it’s not convenient. In the United States where parking is generally available, gas is relatively cheap, and a car is needed for most errands (and therefore readily available), for mass transit has a heavy lift. To gain traction it must at a minimum be more convenient than using a car, which it often is not. The only exception I’ve seen in the United States for regular use has been in Manhattan, New York City where managing parking for a car coupled with the fairly regular train schedules tip the convenience scales in the mass transit direction. Otherwise, only two types of people tend to use mass transit: those that cannot afford a car at all, and those that feel a sense of obligation to use the system for some external reason. Rarely have I heard someone actually enjoy mass transit (there are always exceptions).

The Proposal

I teased the idea in the Urban Mass Transit blog post of a system of moving walkways. When I try to explain it I get a lot of blank looks, but I’m convinced that it’s not because it’s complicated, but because it’s unlike anything anyone has personally encountered. The best starting point would be for someone to read “The Roads Must Roll” by Robert Heinlein. My concept isn’t exactly the same, but the premise and promise of the solution is the same.

Imagine if you could walk to everything in a large metropolitan area. The best way for me to describe the vision is to take you through a trip from your house to your work. It helps if you’ve used a subway system before.

A sample journey

You leave your house and find the nearest entrance to the RapidPath system (dotted every half mile or so) and go down into an underground station. In the station you get on a moving walkway, boarding at a leisurely 1.5 miles per hour. As you continue, the walkway accelerates to a speed of approximately 5 miles per hour. Within seconds the wall to your left disappears and you have access to a parallel moving walkway – one that matches your current speed. You take the two steps to the left and you are on the new walkway. Thirty seconds later the walkways separate and your current walkway starts accelerating.

You do this transition one more time to a walkway that stays at a steady 45mph where there are seats. Your suburban house is 15 miles from the transit hub. In those twenty minutes you’ve answered an email and read the news. You get up from your seat and reverse the process to transition to slower walkways until you’ve exited into the transit hub.

You walk to the access walkway for the line that serves your workplace. Using the same process as before, you board, but because it’s only a mile away, you stay on the first walkway as it accelerates and decelerates at the next two local access points before getting on the access point walkway to exit the station. Your workplace is a few blocks away.

A 16 mile trip took you under half an hour. You didn’t have to park, rent a bike, wait for a train or bus, or walk long distances in the rain. And that day you wanted to bring your bike for an afternoon ride? You just wheeled your bike along the same way. This example would be for a fully underground system, but the walkways could also be at grade level or overhead just as easily. A more technical description of what just happened is covered in the linked Design Summary.

The Rose Colored Glasses

I’m biased towards this solution. What makes me like it so much? Its’ the problems it solves that bother me about current transportation methods and the promise of making every city a “walkable city”. Here’s a summary of why I’m excited and what it solves.

The wait

If you’ve ever ridden any mass transit system, the first thing you give up is your time. Your time waiting for the next conveyance, the time stopping at every station, and time planning your route based on availabilities and schedules. The ideal incarnation of the RapidPath system eliminates all of this wasted time. You get on as soon as you get to the station, you can transfer to express walkways that bypass local stations, and since the walkway always move, your trip is the same during all parts of the day. Access stations could be very small and placed close together without ruining the overall efficiency of the system.

The “ick”

Riding mass transit can be icky at times. The most likely scenarios fall into two categories: icky conveyances and icky people. In this instance the conveyance is a walkway that you really only need to touch with your shoes. This is no ickier than a standard sidewalk. Not necessarily clean, but you can avoid the worst of it. And unlike a stationary sidewalk, the walkway components could be automatically cleaned at the end of each line before it goes back into the walkway system. Icky people will not be eliminated, but they’re much easier to avoid when everyone is moving at the same speed on a walkway. On a bus or train, someone stinky gets on, you’re trapped with them until at least the next stop. On a walkway, you just walk away.

All the Unvalidated Stuff I like to Claim

There’s a host of other advantages that initial work seems to support but needs additional study to validate. The most obvious advantage would a reduction in operating manpower and therefore operational costs. It’s likely that the power requirements would be low as well (dependent on design) further lowering operating costs. The system I’m proposing could be designed so you can do most of the maintenance without stopping the walkways. The proposed design would use a smaller footprint than a subway system and could cost less and be faster to deploy than a light rail system. There are also possibilities for easy expansion, service flexibility, and modularity.

The Big Questions

I’ll be the first to acknowledge there are a lot of unanswered questions about the concept. I’m going to cover just a few of the biggest hitters below including whether it’s even technically feasible, how safe would it be, how much it would cost, would people actually use it, and how do we get it started? There is a lot of work required to answer these questions with a decent level of confidence, but I’ll give you a preview on how I’m trying to tackle each of these questions.

Is this technically feasible?

I’ve mechanically modeled the majority of the technology including the walkway, rails, and stations. I’ve even run some quick calculations on power requirements, cost for rolling stock and infrastructure. For the most part, on an individual technical aspect basis, nothing has raised a red flag. Some of the technical details (such as handrails, walkway separation, end of the line safety, etc.) aren’t quite figured out, but none of it looks beyond what could be accomplished by a good engineering team. An old iteration of the mechanical modeling can be seen in the linked provisional patent for reference on the amount of mechanical design that has been done.

How Safe Would This Be?

This is likely the trickiest question. When it comes to interacting with humans, we are challenged by the frailness of the human body as well as with their penchant for inadvertent self-harm. I’m proposing that the walkway could go as fast as 45mph, which is fast. But it’s not absolute speed than kills – it’s relative speed. In a steady state walkway, we can make everything touchable (walkway, rails, walls) move at the same speed. The problem is when we open and close the barriers between walkways. The barriers are static, so in some cases moving at 45 mph. Making introduction of an object gradual enough and safe enough at those speeds will be tricky. I’ve played with gently growing walls, systems of deaccelerating rollers, and splitting walkways. All are technically feasible, but it’s not clear what approach will be safe enough for mass implementation at this point. If there’s one technical item that could throw a wrench in the works, this would be it.

How much will this cost?

Since the technology is completely novel, this pretty unknowable. What I have done is roughly estimated the cost of rolling stock and the rail system based on the initial conceptual design, then used some equivalencies for current mass transit systems to fill in the gaps. The swag I’ve come up with so far is that rolling stock per mile (what you stand on) is around $2M per mile, railways (installed) around $3M per mile, and electrical infrastructure around $0.5M per mile. That’s an initial capital cost of around $5-6M per mile. I suspect moving handrails and partitions probably double the cost. I’m obviously way off since the silver line (an above ground train) costed over $200M per mile, but I don’t think I’m off by a factor of 15 either.

Operating costs are another calculation. I considered the power requirements, maintenance costs (estimated as replacing individual walkway segments) and manpower. That all boils down to around $9500 per mile of track serviced per day. Compare that to the approximately $38,000 spent per mile of DC metro track per day, again I’m certainly missing something, so I might be off by a factor of 4, but given my conservative assumptions it seems unlikely.

Would People Actually Use It?

This is more of a philosophical question. I believe (and it is a personal belief) that if the system is more convenient, cheaper, and safer than cars people will use in the droves. That is predicated on the sort of fully fledged system in the usage example. I don’t think people like traffic and many don’t even like driving. Not the mention they could read the paper on the express lane (maybe if they have a fancy self-driving car they could do that too), but they also don’t have to deal with the hassles associated with car ownership. At that point a rental car model starts making more sense for family vacations or the trip to the home improvement store.

How do we get started?

I think success breeds success, so starting small would be my preference. A single lane accelerating walkway in some public area like a downtown shopping center, convention center, or replacing terminal connectors at airports would be baby steps. That significantly reduces the required upfront infrastructure improvements required, capital investment, and risks if something should go wrong. There also seem to be plenty of opportunities where a moderate speed walkway (one that accelerates to 5mph and back) would be hugely beneficial.

The step after that would be to replace some isolated subway system line with a single acceleration walkway and a constant speed express lane. There are many smaller metro systems throughout the United States that would benefit from this system.

Final Thoughts and a Plea

If you made it this far, wow, I’m impressed. Either you’re completely blown away by how idiotic this all is and you have some poignant (and constructive) reasons I’m out to lunch or you’re at least intrigued by the possibility and have thoughts on how to move this forward. I’d like to hear from you either way. Any start to the conversation is a good start.