« a future for very very long buses? | Main | the silicon valley shuttles, revealed »


Feed You can follow this conversation by subscribing to the comment feed for this post.


I still don't get it how it's supposed to be mathematically/geometrically impossible to do 100% of transit in small vehicles with, say 10 people in it, if it is possible today to have >50% of transit in slightly smaller vehicles with 1.3 people in it.

Heck, in most of the United states today, if everybody were car sharing with 4 people per car, that would basically be the most efficient transport in terms of space and energy.

I understand an argument about cost, but not one about geometry.

Daniel Howard

My feeling is that any "vision" of flexible services would be to compete with car ownership instead of existing transit. And in that, they have an advantage over personal automobiles in that they don't require dedicated parking space per trip. They could aggravate peak-period congestion, though some percentage of peak-period congestion is based on drivers circling in search of parking.

The vision also works for low-density places where large buses run circuitous routes and at peak usage max out at around 10% capacity. (My local bus in Northern California.) These spaghetti routes are so off-putting that until I asked Google for a route, I hadn't an idea that the local bus could take me to the Light Rail ...

My vision would be one of a flexible service fleet that could schlep you from at or near your house either to a nearby destination or to a high-capacity, frequent-service line. The decisions would likely be cost based, with some economic concessions made for disabled people, who may be better served by long-range point-to-point flexible service.

I think a transit consultant may wish to be careful not to come off as pooh-poohing an idea in its entirely: criticize an over-arching vision but indulge in what parts of the vision could realistically help to improve transit.



The annoying thing about PRT is that its backers seem more interested in going after transit revenue streams than they do in going after highway revenue streams--even though PRT (in its various flavors, including driverless autos operating on unmodified streets) is far more interesting as a replacement for the personal auto than it is for the bus or train.

Aleks Bromfield

@ant6n: Rather than thinking in terms of ceilings or floors or other hard limits, I think it makes more sense to think about this problem in terms of relative efficiency.

At any given level of mobility demand (above a certain threshold), it's more efficient to meet that demand using a highly-connected network of fixed-route services than by using any sort of flexible service.

In general, most large American cities have less fixed-route service than they need, rather than more, at least in the urbanized area. (Conversely, outlying areas may have more fixed-route service than they need, often because local politics dictates that it would be "unfair" to provide more service to the city.)

To the extent that flexible-route service replaces fixed route service in dense urban areas, it will almost necessarily make mobility less efficient in those areas. I doubt you'd argue with that.

Now, to the extent that flexible-route service replaces private automobiles, yes, it would make mobility more efficient. But in my experience, there are two main reasons why people choose to drive in a large, congested city. First, they like the ability to come and go whenever they want. High-frequency fixed route services can inherently do a better job of providing this than flexible services. (And if you think people will happily board a bus that might drive a few miles in the opposite direction before heading to their destination, think again.)

And second, there are reasons to drive that aren't directly associated with getting to your destination as fast as possible. Maybe you've got kids with strollers/carseats, or maybe you or your spouse needs a wheelchair, or maybe you're making a big shopping trip, or maybe you're heading to or from an area that has poor transit service.

In all of those cases, even the best transit service in the world won't attract everyone out of their cars. (Even in Manhattan, I believe about 20% of households own at least one vehicle.) So realistically, it's reasonable to expect that flexible-route services will come at the expense of fixed-route ridership, rather than private automobile drivers.

Aleks Bromfield

@EngineerScotty: Take a look at the "comparison" page for the "Ultra" PRT system (currently in use at Heathrow):


The #1 item on their page is "convenience".

Needless to say, if your objective function is "minimize wait time", a PRT is going to seem very attractive.

That said, it's also very interesting to see this page:


The airport has 67 million passengers per year, or over 180,000 per day. And yet Ultra serves only 800 passengers per day. Clearly, this is not competing with fixed-route transit.

Chris M.

I somewhat agree with ant6n.

While replacing a very two minute frequency standard bus size service with one minute frequency at half the size would barely be an improvement in service, replacing a 15 minute frequency service with 7.5 minute frequency mini bus would be a noticeable improvement. Even LA's "Metro Rapid" frequent buses have frequencies of about every 15 minutes.

But of course, if Jarret's "geometry" includes cost, then this wont work.

Eric O

On the face of it, I definitely can see the attraction of the NETWORK_LA proposal, but it seems to be confusing the hardware for the middleware. Instead of harnessing the power of big data to manipulate the transit route, how about letting the modes operate to their max efficiencies and build the middleware to focus on how you use THE CITY.

FREE the pedestrian to use the city. Lose the vehicle. Find the city.

Am I the only one who finds Wen and Gayle's idea to license real time data chilling? That, if anything, is a recipe for inefficiency and, ultimately, loss of choice, loss of innovation and loss of freedom. Much better to encourage innovation through open source middleware platforms, such as Flybit's Mobile Transit Companion, which feeds the most valuable information on the spot to the transit user in real time using contextual data. The more sober strategy of companies like Flybits is to free the USER, not the transit.


So the supposed geometric impossibility of on-demand transit with comparatively small vehicles boils down to the assumption that such a transit mode would replace mostly/only high ridership bus ridership, but no car ridership. That seems like a strong assumption to me, making the claim of 'inherent geometric impossibility' a bit weak.

I am not really buying the efficiency argument, either, although it is not very related to the geometry issue. You claim on the one hand that there's demand for more high capacity bus lanes, but say on the other hand that people don't want to travel a couple of miles in the wrong direction to get to their destination. But, using demand-responsive transit, you'd use small vehicles filled with people that travel on journeys that have the most similar route possible to yours - so the higher the demand for fixed routes, the less route deviation there should be on your route using demand responsive transit, because there are more people who want to make a journey similar to yours.

I'm not convinced DRT could work, or convinced that it wouldn't, but I find the arguments I've heard against it a bit weak. Well, except the cost argument.


There's a pretty good analogue to this whole DRT model already in operation: airport shuttle vans. They connect a central point (the airport) with outlying areas, and provide door to door service by deviating on the way to take individual passengers to their destinations. The impact this has on travel time varies considerably, with the most efficient possibility being a cluster of passengers in a neighborhood and then a long run on a freeway, but even then, the first person being picked up has a journey that can easily be an extra half hour to hour longer than the last person. Reservations are required for them to pick you up on the way to the airport, obviously, but not strictly necessary in the opposite direction.
But keep in mind that this is a much smaller and more manageable problem: the airport is going to be at one end or the other of all the trips. In the general case, the size of the problem space increases considerably, since there are now a quadratic number of origin-destination pairs, and since ridership is going to be much, much higher if this replaces transit and driving.

Alden Wilner

To me, the final sentence of the "Fast Company" article was telling:

“What might cities do with all their BIG data that currently sits unconnected and underused?”

In other words, we have an answer looking for a question. How can cities use all this data? Surely there's something we can do with it... let's reform transit!

And the last paragraph of Jarrett's post also was the most significant: driverless cars will change everything. Now there's an answer looking for questions!

Andre Lot

I think many people stonewall any promise of driverless personal vehicles (not necessarily on the form of a 4-wheeled built-to-survive-crashes, mechanically wheel-steered machine) out of hidden or at least concealed agendas.

First, let's notice what is major about "self-driven vehicles" is less about computerized pre-set control of the mechanics of a vehicle and more about the ability of a computerized system to deal with a physically open system. So in that aspect the Google car innovation is much more important than that of Ultra or other PRTs.

Then, we get the stonewalling crowds against possibilities brought by these systems:

1. Those who resent the possibility cars might become a service you pay by use instead of a major "appliance" you own and use exclusively. Throw in here those who subscribe to the paranoia club about "government tracking of citizens" or "corporate control of your movements".

2. Those who are concerned or fearful that an ultimate successful system of articulated, automated vehicles will "enable" urban design forms they don't like (like making "sprawl" viable with easy transportation that is not an oil-based car).

3. Those who are on the fanboy camp and resent some system that might displace transit as they know it, and drastically reduce labor needs of transit. As many people on the Transit and Transportation blogosphere have special personal interests in the system as employees, heavy users, admirers or contractors, this group is overrepresented in blogs, forums etc.

4. Those who want more transit for merely social engineering purpose such as "make people see people with different appearances every day to become more tolerant instead of travelling in a metal cage that isolates them".

Matt D

Matt D's summary response to the Network_LA plan: that's why you're architects and not engineers.


My limited experience with with airport shuttles is that they just plain suck.

Usually these airport shuttles tend to cost almost as much as a taxicab (sometimes actually more than a taxicab if you have multiple passengers traveling together) for a service that is only marginally faster, on average, than a regular bus, but vastly more unpredictable.

I used it twice in the city of Houston, not known for its great transit system. By car, travel time from the airport to home is about 35 minutes. The first time I did it on a shared-ride shuttle service, the trip took 35 minutes after a 30 minute wait. The second time, the trip took 2 hours 45 minutes, again after a 30 minute wait.

After that second time, the shuttle company permanently lost my business and I switched to public transit. Even though it took an hour and 45 minutes to get home (and required 2 transfers), it was a vastly more pleasant experience than the shuttle for about 1/10th the price.

Why? First, all three routes involved (2 buses and the light rail) provide frequent service if the plane lands anywhere close to rush hour, so all three waits were minimal. On the airport end, I even had a schedule, so I could make decisions like whether to stop at the bathroom or buy a newspaper to further minimize wait time. Second, all three transit routes involved are very predictable in how long they take, since they follow the same fixed route every day. So the anxiety of not knowing whether you're 10 minutes or an hour away from home for the entire ride is vanished. Third, the fixed-route bus system provides flexibility to spontaneously make stops along the way so it feels freer than riding the supposedly "flexible" service where I'm stuck on there for however long it takes to get home without the ability to get off. For instance, on my 2 hour 45 trip, I got extremely hungry and thirsty, but lacked the ability to get off, grab food and/or water, and catch another bus. This is something that with the fixed-route service is easy.

Bottom line - fixed-route transit routes are much more usable than flexible routes, and if a fixed route doesn't work for you, what you really need is not a flexible route, but a taxi.


LOL, Matt! :-D Why am I not surprised that architecture foundations, architecture writers/teachers, and head-in-the-@$$ architecture schools like SCI-Arc are promoting Network LA, or that this absurd stunt was drawn up by an architecture firm? The "cutting edge" design firms are totally seduced by "technograndiosity." That is, the practicality, utility, and feasibility of a technology doesn't matter nearly as much as its retro-futuristic sexiness! Seems like this deficient thinking is also reflected in the "bold" and "innovative" buildings these guys produce - they can't keep out water, they don't age well, they don't work well spatially or circulation-wise, but they sure are flashy in an adolescent sort of way! "Peacock technology (or architecture)," I call it. Certainly flashy... but useless. I think it was Michael Setty who popularized the term "gadgetbahn" for these kinds of stunts.

As for the inevitable distraction of SDVs in the comments here (and elsewhere where grandiose stunts like Network LA are promoted): why all the prattle over SDV networks and how we should start planning them when THERE IS NOT A SINGLE SDV IN ORDINARY, REGULAR USE YET? These people are putting the cart in front of the horse! We didn't start ambitious transcontinental railroad schemes until AFTER railroads had become a popular, proven technology. We didn't start paving roads in earnest until AFTER the bicycling mania had become widespread. We didn't start building parkways and highways until AFTER the car had become commonplace. Once there are several thousand private SDVs making use of our existing roads, THEN we can distract ourselves with building specialized infrastructure for them or modifying transit systems to make use of SDVs. We still don't know how/if the technology will ever scale up. So until then, can we shelve these ludicrous neo-PRT "network" schemes and just try to fix the transit we already have? Especially since, for non-drivers, taxis are already pretty good at non-bus and non-train tasks?

Dexter Wong

Such fantasies are not limited to Los Angeles, a marketing specialist wrote an article in the Honolulu Weekly touting that he could solve transit woes by raising gas price to $7/gal. and use the excess to fund a network of small shuttles and big luxury commuter shuttles that would be demand-responsive. How this would work is anyone's guess, but I imagine residents would revolt if gas prices rose to $7!


To the extent that flexible-route service replaces fixed route service in dense urban areas, it will almost necessarily make mobility less efficient in those areas. I doubt you'd argue with that.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.


Post a comment

Your Information

(Name and email address are required. Email address will not be displayed with the comment.)

the firm

Jarrett is now in ...

Related Posts Plugin for WordPress, Blogger...
Related Posts Plugin for WordPress, Blogger...