Comments on Rail transit modes fall on a continuum - Greater Greater Washington

Comment by Mike C

Fri, 23 Oct 2009 10:46:18 EDT

@Alex B:

You can get benefit out of PRT even if it's on a straight line. The benefits will not be as significant, but there will still be some benefit due to the efficiencies of driverless, on-demand operation. And a line can always evolve into a network.

But I'm not arguing "You should have PRT", I'm only saying "You should not dismiss it based on flawed assumptions".

@BeyondDC:

You got it right, but backwards. It combines (most of) the convenience of cars with the efficiency of transit. In other words, the best of both worlds.

For example, ULTra has done years of testing on its test track, so energy usage per vehicle mile is known very accurately. When you combine that known energy usage with the worst case real-world ridership scenario, PRT would use significantly less energy per passenger mile than the best US light rail, and 1/4th that of average US light rail? Since these numbers are based on measured energy usage and worst-case ridership, there is very little to dispute there. But even if they are off by a factor of 4, it's still no worse than average US light rail energy usage.

@architect:

Real numbers are coming: Korea, Sweden (Google translated link), and UAE are planning city-based systems to be deployed in the next 5 years, all different PRT vendors. And there are half a dozen US cities actively investigating it as an option. Two of these effort involve billionaires with a lot of financial and political will, so there's a good chance they will get built.

Real numbers are coming, sooner than you think. :-)

Again, email me if you want more detail: transenth@hotmail.com

Comment by цarьchitect

Fri, 23 Oct 2009 10:06:01 EDT

SHHHHHHHH!

All PRT stats are theoretical. I WANT REAL NUMBERS BEFORE YOU HIJACK THIS THREAD.

Comment by BeyondDC

Fri, 23 Oct 2009 10:05:46 EDT

I've said it before and I will say it again: PRT combines the efficiency of private cars with the convenience of public transit, which is to say it is neither efficient nor convenient. It's a terrible idea.

Furthermore, regardless of what the people who hope to sell you a PRT system say, it is going to be extremely expensive to install a whole second level of infrastructure on every street. Anyone who says otherwise is using fuzzy math, or they are talking about something much less substantial than "real" point-to-point PRT.

Also, for the record, we already have a perfectly good PRT network. It is called the taxicab, and provided you have adequate density in your neighborhood it works very well, without requiring one cent on new infrastructure.

Comment by Alex B.

Fri, 23 Oct 2009 09:51:29 EDT

You can't call it a fallacy when there's not a single, functional example to back up the assertion. Every kind of engineering project, whether highways or transit or bridges or tunnels ends up running over budget - particularly when attempting something new.

The other problem with the concept of PRT is that it gives you point to point transit. This, of course, requires a full network of guideways - all of which are quite expensive. Again, you shouldn't be comparing PRT guideways to transit guideways, you should be comparing them to a road - since that's the more interconnected local network. Both cars and transit use local roads as their end distributor, either for vehicles or pedestrians. They're quite cheap in the grand scheme of things.

Again, since you've got these relatively expensive guideways, and PRT travel will be limited within that network, you're left with the logical conclusion that the best application for such a technology would be in a contained, campus-like setting.

For actual, urban use, I suspect we'd get far more value in attempting to get automatically controlled cars - that way, you've got expensive vehicles on a cheap network (local roads) rather than expensive vehicles on an expensive network - not to mention that you could then take your robo-car off the network and drive it under manual control, which of course you can't do with a PRT vehicle.

Denying the fundamental mis-match between guideway costs and network density is awfully bold, since that's the single most obvious reason such a system has never been built. You need to build all of it to get the benefit, and doing so would require a huge initial investment in a dubious and completely unproven technology.

But I'll bet it can be the cutting edge in airport circulators.

Comment by Mike C

Fri, 23 Oct 2009 09:42:25 EDT

@Alex B.:

That's a fallacy. PRT is no more expensive per unit capacity than light rail. A 200 passenger train running every 7.5 minutes is 1600 passengers per hour maximum capacity. PRT vehicles spaced at 3 seconds and carrying an average of 1.4 passengers per vehicle is 1680 passengers per hour.

You can have larger trains and higher frequency, but that significantly adds to rail capital costs, and for those added costs you can simply add more PRT guidway coverage. So PRT is competitive, on a cost per capacity basis, with light rail systems.

In my opinion, PRT is (currently) NOT a substitute for heavy rail, which is much higher capacity than light rail. With operational experience, PRT technology may evolve into higher capacity systems, but for now there are plenty of moderate-capacity applications which PRT can handle well.

The idea that PRT is too expensive for the capacity it provides came from Professor Vukan Vuchic, who is otherwise recognized as a transit expert. I've read Vuchic's analysis of PRT and he just plain got it wrong. He may be an expert on trains, but he doesn't understand PRT.

(I can elaborate on any of these points if you like - e.g. how Vuchic got it wrong - but this forum is not the place for such extended discussion. Feel free to email me at transenth@hotmail.com if you want to discuss further).

Comment by Mike C

Fri, 23 Oct 2009 09:20:08 EDT

@Ã‘Â†arÃ‘ÂŒchitect:

That's fine with me, but when someone posts that absurd lightrailnow article as evidence of PRT "infeasibility", they're going to get a discussion, because that article is nothing but an attack piece full of disinformation, authored by people with a financial stake in seeing PRT fail.

For those who are interested in a more balanced treatment of PRT, see this recent Boston Globe article.

Comment by Alex B.

Fri, 23 Oct 2009 09:12:51 EDT

The basic problem with PRT is that you've got a really expensive guideway paired with low capacity vehicles.

Conceptually, the only way that makes sense is in contained, campus-like environments, such as airports.

Comment by цarьchitect

Fri, 23 Oct 2009 02:35:01 EDT

@ Mike C:

Then let's sit tight until the Heathrow system opens. No discussion of PRT until there are results we can judge.

Comment by Mike C

Fri, 23 Oct 2009 00:37:47 EDT

Cavan:

PRT - HA, there I mentioned it! Imagine that - someone bringing up transit alternatives in a discussion about transit! :-)

The LightRailNow PRT paper (which you link to) is complete bunk. Their entire thesis is based on the assumption that PRT cannot operate at closer than 15-second headways. In reality, three separate systems have received regulatory approval at less than 3 seconds headway, and one is soon to open at Heathrow.

That's a 400% error by the folks at lightrailnow, and it's never been corrected. How can anything else in that "analysis" be trusted?

In any case, in the next decade at least a half dozen PRT systems will be constructed on 4 continents, so any moratorium on PRT discussion will be difficult to enforce. PRT will be part of the discussion, and that's a good thing, because it may fill a significant transit niche and make all of transit better.

(disclaimer: I am a PRT proponent and frequently comment on discussions involving PRT)

Comment by Squalish

Thu, 22 Oct 2009 14:04:20 EDT

The Schwebbebahn is technically a model of "Suspended Monorail", which functions more like an "El". Then there is the suspension suspended monorail, whose role is more unique, which fits somewhere between monorails(concept), "El"s(urban penetration), streetcars (ease of stop), and aerial tramways (construction, ease of topographical transversal).

On that note, aerial tramways (distinct from "gondola lifts" used as people movers on ski slopes) are certainly more significant than cable cars, and deserve to be on this spectrum. They use the same gripping-cable means of propulsion.

Comment by Steve

Thu, 22 Oct 2009 11:51:23 EDT

Good point Alex B., which gets at a more fundamental problem - Engineers and Planners define services slightly differently.

For example - San Diego's SPRINTER. I, from an engineering background, call it Light Rail. It does not meet Crash Criteria to mix with freight, and therefore needs all attendant separations and platform designs. Someone from a planning background would most likely call it Regional Rail because of the frequent service and features of the corridor. Both names are correct within their context, but incorrect to the opposite profession.

Comment by Alex B.

Thu, 22 Oct 2009 11:05:31 EDT

Steve - All the more reason to identify systems by service characteristics (speed, capacity, station spacing, frequency) rather than technology.

It's also worth noting that one system/technology can (and often does) fall into several categories.

Comment by Steve

Thu, 22 Oct 2009 10:35:49 EDT

An important fact missing from your discussion - FRA (Federal Railroad Administration) Crash Criteria. This is the ultimate division between Commuter Rail and all other modes in the US, because trains that meet FRA's standards can freely mix with freight trains, while those that cannot must take special precautions (such as NJT's Riverline) or be wholly separated. That is why, though it travelers long distances on commuter patterns, Washington Metro is Heavy Rail. And, though it has short headways with travel in both directions, SEPTA Regional Rail is considered Commuter Rail.

This distinction does not exist in Europe, hence why modes are blurred and mixed a bit more. But Europe also has much smaller, less-frequent freight trains that allow such a system.

Comment by Froggie

Thu, 22 Oct 2009 09:57:15 EDT

So what exactly is the division between Lightrail and Streetcar

Typically, Light Rail has its own right-of-way or its own dedicated lane, while streetcars typically share the lane with other vehicles.

Comment by ah

Wed, 21 Oct 2009 22:28:46 EDT

J - Don't forget the previously elevated Orange Line, which shared rail with the Green line in the downtown area, but has since been placed underground, other than for the SW corridor area.

Comment by Kk

Wed, 21 Oct 2009 22:27:57 EDT

So what exactly is the division between Lightrail and Streetcar; both of them at times can have the attributes of the other depending on the area.

For example Baltimore within downtown it pretty much acts like a streetcar for some portions so if there are portions of systems that have both designs that classify something as a lightrail or streetcar which is it.

Most modern streetcars and lightrail cars look exactly alike except for a few minor changes such as the track gage so what makes them different.

Btw what the hell is a metro it seems like that is up to the choice of the builder some are
light rail
streetcar
subway
rapid rail
regional rail
commuter rail

Comment by J

Wed, 21 Oct 2009 20:24:12 EDT

People love to make categories and draw lines, but its so arbitrary, so I dont get the point. Why are the distinctions important? There is a minor bit of importance when it comes to which rail laws apply, and that is usually defined by freight running. Of course, you have the san diego trolley....which shares a line with freight!

Boston is a good example of "whats the point". The green line. Underground subway which was developed in heavy rail style...because the plan was to convert it. Median running light rail. Above ground fully grade separated rail with 55mph speeds. Street running in mixed traffic. All with the same cars, all the same line. Thats 3 names in your continuum.

Then the blue line, which by your standards is subway/heavy rail....except half the line runs with overhead power (the rest is 3rd rail) and the cars are as short as street cars because the line used to be a street car line.

Then the red line was developed as a subway/heavy rail, but in the 70s expanded to giant park and rides with stations miles apart, aka rapid rail.

Then you have the commuter rail system (you call it regional rail). The franklin line is getting 4 new stops, which will make every stop less than a mile apart, and all within the city of Boston. Service is to run every 20 minutes....but using the same trains that continue on to rhode island! Yet today the line only runs on weekdays. What would this be called?

Now this is just one city.

There are so many hybrids available that do so many different things, theyre impossible to categorize. Like the train that turns into a bus when the tracks end (japan).

Perhaps train capacity would be a better way to separate them.

Low, including people movers, street cars and light rail.
Medium, including subways, and rapid.
High, including commuter and intercity.

While a commuter train can hold 1,000+ passengers, a trolley can only fit 120. Thats a more significant distinction.

Comment by w

Wed, 21 Oct 2009 15:59:02 EDT

Boots-

glad to see an American with an open mind- I have seen the Schwebbebahn in person and it is most definitely a rapid rail type of thing.

It goes quite a ways and connects a number of hill towns including Wuppertal and Solingen- the legendary knife and cutlery capitol of the world.

It is fascinating to watch it in action.

My understanding is that it dates back to the late 1800's and is the oldest system of it's kind anywhere. A friend of mine who lived there said it was not damaged too bad in WW2 and was service was quickly restored . The landscape of this area looks like parts of West Virginia.

I have yet to actually ride the thing- but I can tell you- it zips along pretty darned fast ...

Comment by Cavan

Wed, 21 Oct 2009 15:33:09 EDT

Please don't mention PRT. It has never been built and never will be built in an urban environment. There are no examples of it in the whole world. Morgantown is a failed attempt at it. The project yielded a people-mover. Nothing more. And that's only a very simple, experimental system. It's completely unfeasible in every way and just a pipe dream for its true believers. It's just a distraction that anti-transit groups have used over the years to try to prevent elected officials from approving transit projects through distraction and obfuscation. It's vaporware.

Let's never speak of it again. Here is a good discussion of why the PRT concept is unfeasible. Now, let's get back to rail system nomenclature because it actually exists and works.

Comment by J.D. Hammond

Wed, 21 Oct 2009 15:19:27 EDT

The PRT in Morgantown is all right, but it's the only system I'm aware of at the moment.

Comment by Steve O

Wed, 21 Oct 2009 15:08:52 EDT

And another mode that I think is definitely worth giving a shot to is PRT - personal rapid transit, although there aren't any good examples in the US yet.
http://bit.ly/aQT1v

Comment by Reid

Wed, 21 Oct 2009 15:05:40 EDT

I'd like to see more funiculars. I think 15th St. could use one.

Comment by Froggie

Wed, 21 Oct 2009 14:56:13 EDT

Regarding what Alex posted, there are two additional levels of characterization that can have a significant impact on how a rail line runs, even within "categories" or "continuums":

- grade separated vs. at-grade
- dedicated ROW vs. street running

Comment by цarьchitect

Wed, 21 Oct 2009 14:47:58 EDT

The Commuter/Regional rail distinction makes sense as long as the commuting is overwhelmingly the purpose of service. MARC fits this bill, but LIRR and Metro-North don't, really.

Comment by Jasper

Wed, 21 Oct 2009 14:35:34 EDT

I love that this nice transit oriented blog occasionally turns into a linguistic blog.

Comment by AA

Wed, 21 Oct 2009 13:52:10 EDT

@ah

The Green Line is street running LRT at points - and uses overhead power and smaller cars. Its operation is generally reflective of LRT systems and not heavy rail systems like the Red, Orange, Blue, etc. lines in Boston.

LA Metro has the same duality with the Red/Purple and the Gold/Blue/Green lines. Same with Cleveland RTA.

Comment by Tim

Wed, 21 Oct 2009 13:49:42 EDT

I'm not comfortable with your distinction between commuter rail and regional rail. I think it only works with a few examples.

You mentioned the slight difference with MARC. Yes, its three lines radiate out from DC, which would imply it's meant to bring people from the outer suburbs in to work. But the Penn and Camden lines also bring commuters in to Baltimore and back out at the end of the day. All lines only have weekday service, though you can't really say that the service is only in during morning peak and out during evening peak.

Some commuter rail systems run seven days a week, like New York's LIRR and Metro-North. Of course, it's clear there that people take it inbound in the morning rush hour and outbound in the evening.

SEPTA regional rail is definitely more of a commuter rail, as I see it, in that it brings commuters in from the suburbs and back out in the evening. I don't know, though. The distinctions are fuzzy at best.

So what about PATH? It's almost like what BART and WMATA are, but even more in the direction of commuter rail. Then again, it's a much shorter and more simple system than commuter rail, and obviously, it's mostly subterranian. But it's definitely not a subway, because it has so few stops in Manhattan that it'd be foolish to try to use it for travel within the borough.

Comment by Matt Johnson

Wed, 21 Oct 2009 13:47:11 EDT

@J.D. Hammond,
An excellent point about separating LRT even more so.

I'm not sure about the "Pre-Metro" name, though. In Europe, many cities built LRT systems which they intended to upgrade to full Metro later. Many of these were not converted due to expense.

Calling it "Pre-Metro" indicates that there is intent to upgrade later. That's not the case with most North American LRT systems.

Comment by ah

Wed, 21 Oct 2009 13:46:41 EDT

While this is interesting, I'm searching for the ultimate point. True, there are not only 8 or 9 categories of rail-like transportation. But we draw lines all the time for convenience both in discussion and for legal reasons. From the looks of the FTA's categories, they seem generally satisfactory with perhaps some oddball decisions in specific circumstances (for example, the T in Boston is heavy rail/light rail (green line) combo). But I'm not sure where all this gets us.

Comment by Alex B.

Wed, 21 Oct 2009 13:46:27 EDT

Thinking of transit as a continuum is better than a classification purely by technology, but I think it's better to try and classify based on characteristics. To me, the two most important characteristics would be station spacing and service frequency.

I think measuring these would give you more of an x-y scatterplot than a linear continuum.

Still, none of that addresses network density or integration with land use.

Comment by J.D. Hammond

Wed, 21 Oct 2009 13:44:55 EDT

Boots: I think monorail constitutes a rapid-rail level of service, even if its construction is more like LRT. So I'd put it in the rapid-rail category, along with the Las Vegas monorail and the Vancouver VAL system.

Comment by J.D. Hammond

Wed, 21 Oct 2009 13:42:04 EDT

I'd actually separate the light-rail category further than you have, into "pre-Metro" service in primarily separate ROWs and grades (Seattle, Dallas, St. Louis, LA Gold Line) vs. systems that have significant sections of through-operation in streets and their medians (Portland, Baltimore, San Francisco, LA Blue Line).

Again, this is a continuum, and all of these systems have elements of both. But certainly San Francisco's LRT is most like a streetcar out of these, while Seattle Central LINK is probably the closest to heavy-rail. And while I think there is ultimately a significant distinction between pre-metro and LRT, I don't know where you'd draw the line with some in-between systems.

Comment by Boots

Wed, 21 Oct 2009 13:40:39 EDT

So where does this fall?

http://en.wikipedia.org/wiki/Wuppertal_Schwebebahn

Comment by AA

Wed, 21 Oct 2009 13:02:50 EDT

Also, realize that the NTD modes also represent a reporting function, and are not necessarily the siloed way that the agency thinks about transit 'modes'.

The light rail category has systems that carry a few hundred riders a day (Kenosha, Little Rock) to ones that carry several hundred thousand (Boston Green Line)

Comment by AA

Wed, 21 Oct 2009 12:59:58 EDT

Realize that FTA mode distinctions are driven by outside politics as well. Two commuter rail lines in the NTD are actually pulling FTA funds (the Amtrak Downeaster, and the Keystone) - when you go into the NTD, look at "NEPRA" for the DE and PennDOT for the Keystone.

And Alaska Railroad is represented as a mode too. Wonder why that is? Oh, right. Ted Stevens So it can get a total exemption from accountability measures that the rest of the country's systems are subject to: (From the CFR)

http://www.law.cornell.edu/uscode/49/usc_sec_49_00005336----000-.html#

(a) Based on Urbanized Area Population.Â— Of the amount apportioned under subsection (i)(2) to carry out section 5307Â—
(1) 9.32 percent shall be apportioned each fiscal year only in urbanized areas with a population of less than 200,000 so that each of those areas is entitled to receive an amount equal toÂ—
(A) 50 percent of the total amount apportioned multiplied by a ratio equal to the population of the area divided by the total population of all urbanized areas with populations of less than 200,000 as shown in the latest United States Government census; and
(B) 50 percent of the total amount apportioned multiplied by a ratio for the area based on population weighted by a factor, established by the Secretary of Transportation, of the number of inhabitants in each square mile; and
(2) 90.68 percent shall be apportioned each fiscal year only in urbanized areas with populations of at least 200,000 as provided in subsections (b) and (c) of this section, except that the amount apportioned to the Anchorage urbanized area under subsection (b) shall be available to the Alaska Railroad for any costs related to its passenger operations.