Sunday, June 15, 2008


We urban dwellers know we have a big problem every time we try to get to work. For what seems like hours we become zero efficiency machines with the many horses under our hoods jumping up and down going nowhere. Well maybe not ZERO efficiency..after all we are making some impact...we are obstructing others while spewing emissions from our tailpipes. We are taking up what could otherwise be productive space. We are depleting the world's supply of oil. We are empowering hostile governments...
It's easy to blame the cars......but let's consider, for a moment, another culprit. The roads.
One often overlooked point is that it’s not just that there are too many cars, but rather there are too few roads. While this may seem to be obvious and counter-productive, it raises a couple of important points. First of all, there is traffic because it is too difficult to add lanes in a timely manner. It is too expensive. There may be insufficient space. Now let’s think outside the box and be the three year old who just keeps asking, “why?”
“Well, Junior,” you say, “you need at least ten feet all along the way to add and extra lane..”
“Because it needs to be big enough for cars and even big trucks.”
O.K. now I’m even annoying myself. The point is that we forget that we have a road system designed for big heavy trucks, not the 1.2 person average occupancy of an average car. If you designed roads for commuters in gas sippers only, the lanes could be narrow, the asphalt thin, etc. More lanes, more throughput, faster construction, less money.
One of my main gripes with previous PRT designs is that they seem to forget this lesson. PRT needs to go everywhere a car can go without encountering the “we can’t afford more lanes” problem. It needs to be cheap with a capital C. It must not try to compete with other forms of mass transit between, say two points with only one or two stops in between. That is the realm of trains, or trolleys or buses. PRT should supplement these means by going to where ridership is insufficient to justify larger vehicles. A prime example of where PRT would seem to be less than a great choice is the only active (to my knowledge) program out there, the system to serve Heathrow Airport in London. If you already have people aggregated, and you are transporting them to a single destination, why use PRT?
P.S. Perhaps I shouldn’t use this as an example. In all fairness I haven’t really studied the specifics of that project. Perhaps there are enough terminals on one end and a massive enough parking lot on the other to justify personalized routing. I really don’t know..The point is that PRT needs an extensive network, not just a circular route. That means cheap track, as opposed to the huge cost of expanding truck capable roadways.


timote said...

Heathrow is a poor choice, in the initial implementation. However, if the initial phase works out and you envision a PRT system distributed across all the terminals, all the parking lots, all the employee areas (control tower, etc.), all the rental car locations, etc., then it becomes more sane. Rome wasn't built in a day and all that...

Brendan said...

I agree that there is a need for low cost track, however it is always a challenge to entice organizations (specifically cities and states) to purchase a new form of infrastructure. These cities know how to lay concrete, asphalt, and rail. They don't understand PRT guideway in the least bit...and no city wants to waste time and money on an unproven technology. I believe that there needs to be a transition for cities and towns, something that doesn't require a huge infrastructure upgrade. I guess we could relate it to the introduction of the automobile. If we take ourselves back to the horse and buggy...these vehicles created paths that eventually became roads. It took many years for dirt paths to turn into a paved road and many more to create the network of roads we have today. I can begin to see why PRT companies are going after a dual-use strategy (i.e. road use AND dedicated guideway). It also makes sense why PRT companies are focusing on markets like airports and universities.
Another way to look at this is to see how the railroad evolved. Think about how long it took to get the world to agree on the standard gauge railroad! Hundreds of miles of non-standard track were removed and replaced with standard gauge.

It will be a challenge to agree upon a standard. The transition phase for any PRT company is important and a significant strategic step.

Dan said...

Dan the blogger Responds-

Welcome aboard new poster Brendan. You are right of course. You describe the normal, historical paradigm well. In a world where people form corporations to try to sell proprietary transportation systems things will unfold as you describe. Which is precisely why this blog exists. I do not consider it inevitable that many track specs will exist, so long as we vet the designs completely and impartially, and the designers of potential systems have access to our work. I do not believe that change has to be slow and evolutionary, as long as city planners know they have an army of volunteers who are committed to fixing any problem.
Yeah, we’re a very long way from an army, but a march if a thousand miles begins with a single step. Who would have thought volunteers would write an encyclopedia for free, (Wikipedia) or an alternative to Windows? (Linux)
It occurred to me that perhaps you had skimmed over the part of “About This Blog” that dealt with these open-source aspirations, so I decided that reiterate them in my latest posting, because it’s pretty easy to miss it, what with all of the new posts and all.

cmfseattle said...

1- (60-) the way to divert road funds to PRT is to make PRT the more-attractive choice. my initial inclination is to charge for PRT based on energy consumed (perhaps with congestion/time-of-day discounts): very similar to the familiar gas tax, yet rewards efficiency.

btw, just now seeing your first few posts. wish everyone got PRT.