Lightweight Mass Transit

What would happen if we made mass transit significantly lighter? I’m not talking about shaving 10% here or 15% there, I’m talking about completely reinventing mass transit vehicles with the goal of minimizing weight. What would that mean? Bicycles work, cars work, buses work, many kinds of rail-like systems work, so why make something new?

The first reason is to regain our position as the technological leader in transportation. Innovation is a national past-time. Innovation is how the U.S.A. differentiated itself from most other British colonies and it is how we grew to become a superpower. So many LRT vehicles are purchased from overseas manufacturers. If we create new modes of lightweight mass transit, we can build them and use them in the U.S.A. and sell them to other countries.

Secondly, aside from the trusty bicycle, every transit mode listed above is significantly massive when compared to a human. Walking, bicycles and other human-powered vehicles are at human scale; whereas automobiles, buses and trains can easily overpower and crush a person. It is a national travesty that we have become accustomed to significantly high death rates in our transportation system when there are safer alternatives. Lightweight vehicles change the equation.

The third reason to innovate a new system of mass transit is to utilize modern technology and sustainable manufacturing methods. Cars, buses and trains were all designed over a century ago using the technologies of that time: steel and internal combustion. Just like Scaled Composites reinvented suborbital space travel, the U.S.A. should reinvent mass transit. Make it better, faster and cheaper.

Given those reasons for reinventing our transit vehicles, let’s take a look at the potential benefits.

Lightweight vehicles are revolutionizing suborbital space travel.

Reducing the mass of a transit system saves energy. Reducing the mass of the vehicle linearly reduces the energy required to accelerate the vehicle. So if you cut its weight in half, you only need half the energy to bring it up to speed. Furthermore, if you reduce the mass of the entire system of transit, you are using less raw materials. So you use less energy to process the materials, you use less energy during construction, you use less energy to transport the materials during construction and you use less energy when re-purposing the materials after their useful lifetime. All this energy savings reduces both the one-time and recurring energy costs of a transit system, but a lightweight mass transit system also has its own cost savings.

If you were to take, for example, a modern light rail train (LRT) system and reduce the LRT vehicle to a fraction of its current mass, you could then reduce the maximum load specification of the rail it runs on allowing you to use cheaper rails. The depth of the railroad bed could be reduced and the engineering needed to build the bed is reduced; two more cost savings. This doesn’t just hold true for trains, a lightweight bus-like vehicle could run on a dedicated road that isn’t as thick as the ones in use today. The lighter vehicles do not generate as much wear-and-tear as heavier vehicles, so maintenance costs are less, too. Costs can also be reduced by making a safer transit system.

Many people on the road feel more secure in a larger, heavier vehicle. However, these people are actually introducing more danger into the system by adding their vehicle’s mass to the kinetic energy of a collision. A lightweight vehicle, on the other hand, inherently stops quicker and adds less kinetic energy to a collision. If the transit system features separated paths, where only specific types of vehicles are allowed, that vehicle needs only a known amount of safety reinforcements. That is, the vehicle doesn’t need to have over-engineered safety reinforcement to survive a collision with heavier, vehicles. If the paths are further guaranteed to be one-way, then head-to-head collisions should never occur and does not factor into the safety equations. A safer transit system is also cheaper to insure and will result in less litigation costs.

Finally, a cheaper and safer transit system will draw passengers away from more expensive and dangerous methods of transportation. In turn, increased ridership improves the financial success of the transit system.

Lightweight vehicles can be just as safe.

It’s amazing how focusing on just one design aspect, mass, can have such a significant effect throughout a system. Indeed, designing for less weight is not my idea. The Lotus engineering team has been practicing it for years and the Rocky Mountain Institute claims that reducing an automobile’s mass is the best way to achieve efficiency. Nor am I the first to apply it to mass transit [SIU2006].

This concept opens up a lot of opportunities for discussing some creative ideas on how to move people around. Here’s the kicker for Houstonians: we have some of the most technically adept engineers for designing lightweight vehicles in the world right in our back yard. Engineers at the JSC and its contractors know very well the importance of mass, how to get rid of it and still move the vehicle, occupants and contents quickly and safely.

The sooner we put that knowledge into action, the sooner we can reap the benefits of a better transportation system nationally, and potentially reap the rewards of a new industry locally.