Every transportation technology has both inherent and perceived strengths and weaknesses. With this in mind, and the talk about urban aerial trams and gondolas getting new attention in Seattle, both from long time blogger Matt Gangemi (Matt the Engineer) and two weeks ago from Matt Roewe at the City Builder happy hour, I wanted to start the discussion on STB by talking about the basics, strengths and weakness of aerial trams and gondolas. I’m not an expert on design or construction, but their characteristics can be defined along the same metrics as other modes of transit.
I see this as a critical starting point for any serious discussion about these technologies, because (let’s be honest) most people find the idea of urban aerial trams and gondolas far fetched.
I’ll start off with the basics about the technologies. First, while there are technical differences between aerial trams and gondolas*, the importance of these differences from a rider’s perspective comes down to two things, frequency and stations. There are differences in speed, but I’ll explain why this isn’t very important.
Aerial trams fall into a family of technology much like elevators, with two counterweighted objects, permanently connected by a cable. When one goes up and the other goes down. Elevators, funiculars, and aerial trams all operate on this principle. Portland has an aerial tram, not a gondola. This fixed, counterweighted design means that the maximum frequency of the service is inherently limited by the time it takes the tram to get from one terminal to the other (cycle time). As the length of the aerial tram increase, the maximum frequency decreases. Gondolas do not have this inherent limitation. For more details go here.
Next, while both technologies can technically have stations along the route, the permanent cable connection of aerial trams, between the cab and cable, means that in practice the only viable place to have a mid-system station is exactly half way between the terminals. This is not the case with gondolas which have cabs that are able to detach from the continuously moving propulsion cable. This means that there can be multiple stations, with station located anywhere along the line.
Finally, while speed is always important, the relative short distances these systems typically cover in urban areas, means that the very high frequency of gondolas (every 1 or 2 minutes) in practice trumps the speed advantage of aerial trams. Additionally, gondolas will result in much more consistent travel times for riders, with roughly equal or lower travel times than aerial trams. Travel time consistency, a result of high frequency, is much more important for short trips because wait time quickly makes up a much larger portion of the overall travel time for a rider.
Here’s an example. Assume aerial trams have an average speed of 10 mph** and are roughly 20% faster** than gondolas. The total travel time on a 1-mile aerial tram would take between 7 and 14 minutes, due to the 0 to 7 minute wait time, with an average of 10.5 minutes (6 minutes traveling + 1 minute docking, unloading, loading, and departing, resulting in a cycle time of 7 minutes). The same trip with a gondola would take between 8 and 9 minutes, with a wait time of 0 to 1 minute, resulting in an average of 8.5 minutes (7.5 traveling + 0.5 minute loading/departing). This means that only in circumstances in which a tram rider waited less than 1 minutes would they get to their destination faster than a gondola rider. If a tram rider waited more than 2 minutes, all trips on a gondola would be faster.
In another post I’ll discuss the strengths and weaknesses of gondolas compared to earth bound modes of transportation, and how it plays out in the Denny Way corridor.
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* For the purpose I’m referring to “2S” or “3S” gondolas such as Peak 2 Peak and the preferred alternative selected in the Burnaby Mountain Gondola Transit Alternatives Analysis by TransLink.
** These numbers are at best informed guesses and only intend to illustrate the point of the example.
It’s something we’ve never done before, which is why we’ll never do it. If a mayor proposed it, some dork would nickname him Mayor McTram, and all the comments on every article on the Times website would fill up with negative references about it.
It’s not that this town is full of morons, it’s that the morons get all the attention.
Mayor McTram, lol. Nailed it.
Or Mayor “GoingDownNowAola”
But a Gondola from Capital Hill, otherwise known as the “Swish Alps” to SLU, and/or Downtown would make it easier to walk around town. I always wondered if they couldn’t build a loop, instead of a just up and down system. A cable car version of PMT
You certainly could, but wouldn’t for the same reason you don’t have bus loops – to go the opposite direction means going all the way around.
As a skier in both North America and Europe I am quite familiar with trams, gondolas, funiculars, etc.
On the whole gondolas are a much more pleasant experience, given nearly instant loading when there is no line, and seating while riding, generally less crowding, and ability to enjoy the view. On the tram you have to wait for the next tram, generally there is no seating and everyone is standing, and the design capacity assumes crush conditions worthy of a Tokyo subway.
My perception is that the speed differential is much greater than 20%. That could be perception, but there likely are technical differences that mean a tram can go much faster. Gondolas must be unhooked from the pulling cable at each terminal in order to slow them down for boarding and disembarkation, and then reclamped. In addition, other than the new Peak2Peak gondola at Whistler, generally there are closely spaced towers which I believe also limit speed. Trams are fixed to their pulling cables, and generally the spans between towers are much greater. Also trams almost always have 2 weight carrying cables, which essentially function as tracks, and the tram itself has wheels which run on these. I believe this allows for faster speeds. In gondolas, generally the weight carrying and pulling is the same cable, and the mechanism has to cross wheels at each tower.
Another difference is that there is generally an operator aboard a tram. This could be a safety advantage vs. being locked in a cabin with 6 people you don’t know.
Neither technology is well suited for distances of more than about 2 miles due to slow travel times, and in the case of trams the resulting low frequency due to cycle times. At Whistler the main gondola takes about 25 minutes to reach the peak. I don’t know the distance but it’s probably less than 3 miles.
Yeah so from the reading I did about Peak to Peak and the assumptions used by TransLink in their gondola study two and three wire gondola systems which is new and better than one wire systems. This difference deals with the tower spacing issues.
The ~20% difference in speed I assumed was based off the translink study, which says the maximum speed of a tram is ~22mph and a gondola is ~17 mph.
Remember though that 22 mph is the crow-fly velocity; a factor is needed to deal with elimination of hill climbing roadway curves (at least for the Translink /SFU application.
I’m not getting it 100%. Are you talking about land base travel times via roads or are you talking about the fact that since some of the travel is horizontal it means vertical travel speeds are less?
Compared to a ski area, the Portland tram likely presents a much better and more local example of a tram would work as an urban transit mode.
As an avid skier, I am also very familiar with gondolas. One thing that boggles my mind about a commuter gondola is evacuation procedure.
Gondolas break down, not as often as chair lifts, but enough to be cause for concern. Now on a gondola (I’ll pick on Whistler), like the Excelerator Gondola or the Whistler Gondola (both of which I have gotten stuck for 20+ minutes), they can evacuate the gondolas with rope ladders if it looks like the lifts won’t be working any time soon, as the lifts are usually no more than 30 ft off the ground.
The Peak to Peak, however, is 1500 ft off the ground. I’ve gotten stuck on that for 20+ minutes. That lift, if they needed to evacuate, would require helicopters. Now 1500 ft is unusual, but compare it to the 60 to 80 ft that a Seattle gondola would require.
And how do you justify 10, 20 or 30+ minute waits on a gondola commuter trip that supposed to take ~15 minutes? Not a lot of people would want to risk that. At ski resorts, they make it worth your while with discounted or free lift tickets.
Granted, buses and trains break down too. However, if a bus or train breaks down, you step off and find another way to work. Longer haul buses or trains will probably have a dedicated rescue shuttle to pick up people.
While a gondola is a fun thought experiment, I think it will forever remain that way. City gondolas are best kept as a novelty thing, like the OHSU tram or the London Thames crossing gondola. They just don’t make sense as a commuter choice.
The reason gondolas “break down” is typically from wind. High wind gusts on mountain tops cause gondola operators to slow or stop the line to wait for safe conditions. This is especially true with one cable gondolas, like the Excelerator and the Whistler. This would not, at all, be the case in Seattle. We just don’t have strong mountain-top-speed winds. I can imagine one of our very windy days stopping a 1-cable gondola, but I’ve looked at the wind data and even this would be very rare. It just won’t happen for a 3-cable gondola here.
Not to say a break-down is impossible. There is a back-up diesel motor for power outages, but a mechanical failure could certainly happen. But what transit method is this not the case for? Such mechanical failures are extremely infrequent, and happen deep in tunnels on subway lines or high in the air on sky trains or monorails.
Peak 2 Peak has an evacuation system which is basically a car on a winch that can ride down the track ropes to the cabins. They wouldn’t need helicopters.
I think you’re overstating the breakdown risk of an aerial ropeway. Sure, there are occasionally long stops, but the vast majority of lifts have 99+% uptime, exclusive of operator-commanded stops. Panorama up in BC actually publishes downtime info for one of their chairs; as I write this it is 1.983%, and I’ll bet that all of the stops are operator-commanded due to misloads.
@Matt Gangemi
While wind gusts do cause the gondola operators to stop them, they will, based on their judgment, run the cars slowly, so to not have people stranded in high gusts.
But the times when you are sitting for long periods of time, especially on the more protected Excelerator and Whistler gondolas, are usually due to some sort of maintenance mishap. Whether it’s a legitimate mechanical breakdown, the operators halting to prevent a breakdown or computer breakdown, gondola terminals are very complicated and do breakdown. And a breakdown would be much more noticeable than a bus or train breaking down.
But you bring up a very key point about it being sea level conditions versus mountain top conditions, which would all but remove weather related conditions. But what about other environmental conditions such as moisture in the air or earthquakes?
[Anon] Do you have any source for the mechanical problems conclusion, or is that a guess?
We do, periodically, have windstorms with gusts around 60mph. Would that be enough to interfere with gondola operations?
In my mind, the only real issue with a gondola is the one of stops – a practical gondola generally has very few. It would have to be a direct hub-to-hub link, it’s not appropriate for neighborhood service.
@Matt Gangemi
Mostly from experience and having talked to many lift operators. For example, a warning light might come on to where they will shut down the lift for a bit while determining the source of the warning light/malfunction.
It’s a boutique technology. There might be an application for such a thing somewhere in Seattle (as there is in Portland with their aerial tram), but in general I view this as a distraction from the heavy lifting we need to do with more conventional Light Rail and Street Car systems.
Also, I suspect there are areas in Seattle where we could install a funicular. I’ve always wondered why we don’t have one of those located somewhere locally, unless of course you count the Skagit Valley Incline (which I don’t, but what a shame that you can’t ride it anymore).
I would agree that it is likely boutique technology, suitable either for unique terrain reasons (e.g. elevation change, cross an obstacle where there’s no other right fo way.)
It requires a transfer for all but the simplest trip.
It could be suited to serve a high volume destination as an alternative to branching a line.
Ultimately it cannot be very high capacity.
“Ultimately it cannot be very high capacity.”
Gondolas can have in excess of 6,000 passengers per hour per direction. That’s about the same as 60 buses per hour in each direction. If you can find a system with higher capacity short of grade-separated rail, I’d like to hear about it.
“It could be suited to serve a high volume destination as an alternative to branching a line.” Yes! That’s the perfect application. And why branching off light rail at Cap Hill to SLU and Seattle Center would be such a perfect run.
If you take New Flyer’s published capacity for a DE60LF (62 seated and 53 standing) and put buses on 5-minute headways, that yields a capacity of 1,380 persons per hour. Now, that is only between two discrete points with no stops in between, so in practice the number of people moved can be higher with turnover at intermediate stops.
An 8-passenger gondola at 6 second headways yields 2,400 persons per hour (per direction). And you can scale that up if you want, as Matt mentions.
I was waiting for this to devolve into monorail math and it only took about 12 posts to get there!
Do the math. If you assume a gondola arrive every 10 secs than that is 6 gondolas per minute or only 360 per hour. At 4 passengers per gondola that is just 1440 pass/hr/direction, which is rather small.
If you assume 6 passenger gondolas you still have only 2160 pass/hr/direction, and this all assumes that a gondola every 10 secs is rational.
And even though you load/unload off the main transport cable, you still have egress needs that you have to accomplish in a limited amount of time – and egress takes longer the more people you stuff in a car.
And lets not even talk about ADA compliance…..
The point is that gondolas can scale up (or down) perfectly well, so capacity arguments don’t hold much (if any) weight. Theoretically, gondolas can scale up a lot higher than buses, although in reality if the demand were that high you should be looking at a different mode.
As for ADA compliance, both buses and gondolas are ADA compliant. Buses have lifts or ramps (which, btw, increase dwell time), and gondolas have level boarding with the car either moving at a slow walking pace or stopped momentarily (which, again, increases dwell time).
4 persons per vehicle? I think you’re thinking of these cute things from fairs. If we’re talking about high capacity, we’re talking about these. At 30 passengers each, even one a minute will get you to 1,800 PPHPD. At 30 seconds and 40 passengers per car that’s 4,800 PPHPD.
But all of this is a bit beside the point. Even 1,000 PPHPD (8 person, 2 per minute) would be the same capacity as 5-minute frequency buses, with a much faster trip time. And how many places in Seattle need 5-minute frequency buses to meet capacity? Capacity is just not an issue for anywhere we’d use a gondola in Seattle.
And ADA requirements aren’t an issue either. Wheelchairs roll on just fine.
Gondolas scale up well on passengers per unit, but they scale up really poorly on station-stops per trip. Trains, on the other hand….
And honestly, thinking about the modern evacuation requirements for monorails, both gondolas and aerial trams and suspended trains are probably going to have the same complex safety requirements. It’s gonna end up being just as expensive to build gondolas as to build suspended trains, but less effective. Unless you’re going up a hill it’ll be just as expensive as suspended trains. But it doesn’t scale as well…
just for another example, I’d suggest looking at the installation of the relatively short (couple hundred yards?) enclosed gondola at the Big White ski resort in eastern BC.
its a route/distance/terrain which almost could have been a funicular — but being arial it skips all the conflicts with surface developement and traffic.
while it is at a ski resort, and skiers use it, it does NOT really function as a “ski lift”.
it essentially goes from the center of a pedestrian-friendly, built-out (shops, restaurants, housing, etc) to a second “Base Area”…. which in essence means that it effectively doubled the size of the workable/usable/comfortable pedestrian zone.
it is free, self-loading / unloading, and runs from early morning to late night. there must be 30 – 40 gondola cars (if memory serves) and each car probably holds 8 people comfortably.
there are a couple spots in seattle which exactly this size and scope of system would be a phenomenal asset.
Oooh, self-loading. The gold standard of transit (operations costs drop off a cliff). Funny that almost every elevator in the world works fine without an operator, yet when we make them horizontal we require someone to watch us get on and off. There has to be a way of making these safe enough to load themselves.
somehow the self-load vs. operator-assist thing seems more
driven by the presense fareboxes than it is about safety…..
How does Vancouver’s SkyTrain deal with this? (runs off to search) Proof-of-payment, of course!
Funny that almost every elevator in the world works fine without an operator, yet when we make them horizontal we require someone to watch us get on and off
From an ADA perspective, this makes sense because elevators are invariably at a full stop during loading, whereas gondolas default to a slow-speed boarding window and require that human attendant to bring them to bring them to a full stop.
Of course, you could design them so that every cab detaches from the fast wire, then detaches from the slow wire at a given point on the platform (a box marked by treads for the blind), then waits for a button to be found and pressed before the doors close, but this would eat into your capacity to the point where you’d be clamoring to just hire the attendant again.
I have a feeling there’s more than one solution to this problem, though I don’t claim to have thought through the details. How about the method that those floating log rides use to load passengers? A circle slowly rotating at the speed of the detached gondola. Or you could have a platform with many fully detached and stationary gondolas, and when someone boards it gets in line to be attached. Etc.
Anyway, that’s a dream for the further future. I’m happy to focus on existing technology for now.
Not every elevator stops… :)
In fact, it’s perfectly straightforward to make a horizontal elevator which doesn’t require an attendant. It’s called an “automated cable-hauled train” and I believe some airports are using them.
One problem with fully-detachable-in-operation gondolas is that they’re using, effectively, San Francisco Cable Car technology, which is inherently less safe than most of the alternatives (aerial trams, elevators, escalators, and a bazillion types of railroads). Elevators do *not* detach from their cables.
These days, I think it’s more common for airports to use people-movers, which are basically SkyTrain. The main reason they haven’t drawn much controversy is that they have platform screen doors and are fully grade-separated. Thus, for all practical purposes, no person or object can be on the rails except the trains themselves. (Incidentally, the same is true for elevators.)
For fun, look through the just released FTA list of projects approved for 2013. I still can’t find any gondolas in there, but one for ST’s study of climate change on transportation, as in rising sea levels ($105,000). Maybe they can study how much water the DBT can hold when fully submerged.
http://www.fta.dot.gov/
Great analysis, Adam. Looking forward to the follow-up! I think the gondola topic is a fun one, despite remaining unconvinced that it could fulfil Capitol Hill’s needs. Perhaps I can be convinced otherwise.
This is a brilliant post, Adam. I really look forward to the next post. I’ve not really considered the difference between gondolas and aerial trams before, but it does seem like most systems I’ve seen have been aerial trams.
Of course this will go nowhere since it’s not a toy train that people can stand to make lots of money of… despite the fact that the technology is used in urban settings around the world. Same thing happened to the monorail which people dismissed as “a toy” or an “amusement park ride.”
I don’t imagine anyone wants to build a whole system of gondolas everywhere. They’re great for specific applications where they handily beat out other alternatives.
In our case, we have significant elevation changes between Capitol Hill, First Hill and/or Beacon Hill and South Lake Union and/or Downtown. We also have a significant obstacle of a huge freeway trench in the middle in many places, particularly at SLU.
Add to that the terrible traffic issues at street level along Denny Way and currently low building heights, and we have a pretty great corridor to get folks from somewhere on Cap Hill down to SLU or even to Seattle Center.
I disagree. The Denny Triangle and SLU have lots of development capacity, with developers that understand the important of regional access for them to be able to fully develop them. Because the DSTT only serves the existing downtown core, and the streetcar only really helps people getting from Westlake Station, if I were a developer I would see this having huge potential. Time will tell, its certainly more out there than the streetcar was.
I think there are several places inside Seattle I’d like to see a Gondola application. I’m thinking West Seattle – SODO, SODO – Waterfront (Coleman Dock), Coleman dock – Seattle Center, Seattle Center – Queen Anne Top of Hill, Seattle Center – SLU – Capitol Hill Link Station, Queen Anne – Fremont , Fremont – downtown Ballard, Downtown Ballard -Wallingford – U-District.
While I know there was an argument put forth some time ago that we shouldn’t have competing modes of transport, I disagree. I think Gondolas are an easy and very inexpensive way to construct significant capacity and I think it is particularly suited to Seattle’s on going problem of effective east/west transportation. Some of these lines could also be precursors to our “Subway” system.
Yes, this is ideal for West Seattle! Adds a new public transit corridor without the cost of another bridge.
Now that Matt writes about this from the top of the nest and uses his non-epithetical last name, I feel its time to give my long-held opinion on this gondola proselytism.
In a single sentence: It will work, but we can’t do it yet.
The principle is sound, as Medellín and Caracas have amply demonstrated: for very little money, and in no time at all, those two cities have managed to transform haphazard, disenfranchised hillside slums into legitimate parts of their cities. They have done this by simply making it possible to get between the favelas and the rest of the city in a non-excruciating, non-prohibitive way.
We thankfully do not suffer the kind of isolation of the degree of deprivation that such places have, but the problem we’re trying to fix is analogous: our economy and our civic life suffer from how excruciating and prohibitive it is to move around this city without a car.
Unfortunately, we do not want to be the first United States city to give this a shot. For better or for worse, the speed and thrift of the Medellín and Caracas projects were made possible by lack of political openness in both places, by less stringent engineering-study requirements, by the perception that the lines’ constituents are so poor as to be expendable (or at least non-litigious) in case of a mishap.
You are not going to re-create those lines in North America without everything being designed, engineered and tested de novo, before the “public process” and the inevitable litigation even begins. Ski-resort engineers will prove valuable (as the technology will be most similar and they are used to high all-day demand with “rush hours” when the slopes open and close), but the adaptation to an urban environment will prove (politically) formidable.
There are no worthy urban examples in the First World. Roosevelt Island comes the closest, but it takes a very different form than the gondola-based system we would need here. Portland is irrelevant both because of the technology and because “hospital shuttle” is not a general-purpose transportation need. The London proposal is a condo-development gimmick and has no general-purpose demand either.
Basically, we do not want to be guinea pig here, spending a ton of feasibility-study money only to have the whole thing scuttled by… who knows… (a single air-rights lawsuit? a Congressional pissing match? an arbitrary FAA ruling?)
Our best bet is to wait until another U.S. city gives urban gondola a shot (probably a dying city vainly trying to snare tourists; those things always get green-lit faster than actual transit projects) in a way that happens to provide us enough “cover of precedent” to give ours a chance to actually get built.
d.p., you withheld your opinion on something? Have you turned over a new leaf?
Forgive me – I couldn’t resist. And you shouldn’t have withheld this – I agree with you 100%. Matt has pretty much thought this through from an engineering and practicality perspective and there aren’t too many holes you can poke in it. Its cheap, proven technology with good capacity, frequency, capability and reliability, and has low operating costs.
Legally and politically, however, this will be played safe. No matter how well this proposal is described, I think the public still will think its a joke, thus the political fear. And d.p. outlined some of the potential legal issues.
Certainly a reasonable point, based in the harsh realities of city politics. But I’m not a fan of giving up on something useful because it’s hard. There is no other solution to the Denny corridor, for example, that can solve this problem as well at this scale of cost. That makes it worth doing, even if it’s hard to do.
The test cases have already been done. Starting with the millions of hours of use as ski lifts and amusement rides, onward to the 3rd world, then the Koblenz Rheinseilbahn in Germany, and now the London installation. And I wouldn’t discount Portland – the politics required to get their aerial tram must have been very similar to what we’ll go through.
I 100% agree with you about Denny, and fortunately I don’t think it will be long until we see First-World applications of the concept that are actually relevant to our needs.
Portland really doesn’t cut it (hospital anchor/sponsor, no one else really needed it). And tourist conveyance (even high-volume ones) will never make the point, since they tend to connect a point in the city to a remote site, rather than connecting city-to-city-via-city. The Koblenz Rheinseilbahn wasn’t even permanent.
Koblenz did, as one bullet point in your PDF describes, give industry promoters a chance to showcase cabs in familiar and comfortable urban-transport layouts.
(More here: http://gondolaproject.com/2010/09/14/the-koblenz-rheinseilbahn-part-2-the-vehicles/)
This is a great first step. It will be even more valuable when it exists somewhere for the sake of actual urban mobility.
Getting something built in Europe remains 20% easier and 40% cheaper than getting the same exact thing built in the U.S. They are going to have this before we do. And once they do, it will lower our barriers somewhat; we may still encounter “legislative engineering,” but we probably won’t have to engineer from scratch the way we would be forced to adapt ideas directly from the “scary” Second World.
I’m really struggling with this part of your comment:
Sorry, block quote problem. I’m speaking here specifically about this part of your comment:
“the speed and thrift of the Medellín and Caracas projects were made possible by lack of political openness in both places, by less stringent engineering-study requirements, by the perception that the lines’ constituents are so poor as to be expendable (or at least non-litigious) in case of a mishap”
…so poor as to be expendable…
Did you miss my context?: “For very little money, and in no time at all, those two cities have managed to transform haphazard, disenfranchised hillside slums into legitimate parts of their cities. They have done this by simply making it possible to get between the favelas and the rest of the city in a non-excruciating, non-prohibitive way.”
I will admit that those particular words could have been chosen more carefully. Chavez has a populist bent; the Medellín authorities no doubt were thinking of the interests of the residents as well.
They could also easily force through clearance of any obstructing dwellings, and build to the cheapest possible standards, with no fear of legal or political reprisal. That’s the advantage of being a dictator — even a benevolent one.
The idea that the engineering standards would be lower is ridiculous.
The things were build insanely fast and insanely cheap, on extremely difficult terrain with people living on it.
I would love to be proven wrong. Really. But I’m not going to take on the faith of a single-minded modal advocate that these systems would have passed muster in the First World; I will need actual evidence!
Regardless of the question of build quality, the Medellin gondolas are still effectively point-to-point low-capacity transit. The line with the most stations has a total of *two* intermediate stations.
And the safety standards are *clearly* not up to modern US specs for fully detachable single-wire gondolas.
While I agree with your second point, it should be noted that “*two* intermediate stations” is precisely what is being proposed for the Denny corridor, and over a similar total distance.
I really like the ideas of “Gondolas” but I beg to know what makes this technology more suitable than a High Capacity PRT system like “Vectus” where you have your offline stations and speeds that can travel up to 70mph?
Because the cost of building trillions of miles of PRT guideway would be equivalent to the combined GDP of half the planet.
Because you don’t buy the gold-plated hovercraft when you could buy a pair of wading boots.
Because infrastructure that can be expanded incrementally are worthwhile, while infrastructure that can only work by replacing every street in existence simultaneously is useless.
Because real ideas solve real problems, while lying in your dorm room dreaming of a squeaky-clean science-fiction utopia solves nothing.
Hey, you “begged to know…”
To be less snarky and more clear, PRT in places like Heathrow Airport will be awesomely useful. PRT could even work for sprawling but self-contained environments like the Microsoft campus (although one would be correct to wonder why the Microsoft campus was built in a manner that created such a pressing intra-campus movement problem in the first place).
PRT will not work in mixed-use environments with many competing spacial interests, where the guideways would need either to replace every existing roadway or to glide above them at great expense.
The gondola paradigm glides above existing infrastructure with a minimal terrestrial footprint. As Medellín and Caracas have illustrated, this is great when the circumstances (medium-high need, medium-low funds) intersect.
Once you start investing in fixed guideways with inherently larger footprints along each ROW, you need to be able to maximize capacity and accessibility while minimizing the number of ROWs you use. PRT proposes to do the opposite: to maximize the number of ROWs while offering sub-optimal capacity along each one.
This makes it expensive and wasteful in the real world.
The Microsoft campuses sprawl can be partly blamed on it being built as a series of haphazard expansions and acquisitions of surrounding office parks, rather than as a centrally planned campus.
They’re also restricted by Redmond zoning in that area, which, even after grabbing all the density bonuses, only allows a FAR of 0.55 for “software publisher” uses, and mandates 2-3 parking spaces for every 1000sqft. By comparison, a residential use in the same zone is allowed a min-maxed FAR of 4.
They’ve had to build a private fleet of taxis and fixed-route shuttles to facilitate employee mobility around the campus. Had they forseen their explosive growth, I suspect they would have built differently.
The thing is, we *have* trillions of miles of PRT guideway. It’s called every arterial and freeway in every city in the US, aside from the trivial portion which is reserved for HOV/transit.
I have yet to hear any argument for PRT which is anything more than technology fetishism.
Anyway, the purpose of transit is to provide the greatest mobility in the least amount of space (as in land area). If space isn’t an issue, then transit isn’t worth the money (except as a social service). PRT is not space-efficient at all, ergo it is not a viable solution for cities’ mobility needs. That’s all there is to it.
One of the challenges the monorail proposal faced was the fire department demanded catwalks for evacuation. Why would the fire chief sign off on a gondola?
They could run over to Spokane and talk to the fire chief over there. Spokane has had a little tourist gondola (slow, non-detachable technology) running over the Falls since 1974.
What’s going to catch fire on a gondola? The cabins don’t contain a propulsion system or any high-voltage wiring and are made of steel and glass.
[Jason Rogers] above tells us that the Peak-2-Peak gondola has a car that can run out on the wires to rescue you, if we go with a 3S system. With a one wire system, I suppose we might have to run it low enough for fire ladders to reach. Or we talk to Spokane and find out their solution. These are not unsolvable problems.
If an evacuation were necessary, ski areas use a variety of systems all involving throwing ropes over the cable and lowering people down. They also usually have someone climb the towers, clip onto the cable, and shimmy down to the cabins to assist. Systems with very long spans or extreme/otherwise inaccessible locations (i.e. over water) usually have a rescue car like I described for Peak 2 Peak.
Without going into the details, it is usually possible to fix all but the most serious problems to the extent that you can run the gondola to clear the line, and then do the heavy-duty troubleshooting/repairs once you’ve gotten everyone off. Fire department not required!
I am obsessed with this idea, think its wonderful and wish it would happen but doubt it will. It has less of a footprint than a monorail or any other form of moving folks around for the most part with the exception of buses.
I love it, it would move both tourists and locals and it would look spectacular as well as unusual.
Let’s now spend ten years discussing it!
Tim
Kind of an aside, but I wonder if we might finally be able to use our system of gondolas, which I’m all for by the way, to get rid of the Blue Angels once and for all.
On a more serious note, Lake Union is a floatplane airport. I wonder what would need to be done routing-wise to avoid a conflict there? I’m imagining that a line between Capitol Hill and Seattle Center might get pretty close to the glide path to the lake.
Though I like that floatplane airport, this is exactly the sort of thing Matt Yglesias is talking about in his book. We let those few airplanes, a few dozen flights a day at most, dictate policy for a huge part of the city.
If this is going to run near Denny, Amazon is planning 500 foot office towers in that corridor. If those aren’t in the way of the flight path, surely a gondola could be squeezed in.
It’s not an issue. The glide path starts on the other side of the Space Needle, and is around 350′ high at that point. It wouldn’t be a bad idea to put lights in the gondolas just in case, but we’d be easily clear of any restrictions from flights.
You raise an interesting point with regards to lights. Do any manufacturers of detachable gondolas make units where the cabs are powered? I would guess it could be done similar to a cable lighting system where, if we utilize a 3 cable goldola system, the 2 guideway cables provide load and ground, and it’s picked up by the wheels. I’ve just never seen a non-fixed tram/gondola that has cabin power before, so curious if there’s one currently on the market.
I wonder if we can build one of these over Lake Washington — for people and bikes — and have LINK stations at both ends. We could do away with the need for a new 520 entirely.
Gondolas should be used to cross barriers like water or freeways. I was thinking of a short simple system that started at the Broadway link station, ran north up Broadway and took a left at Harrison st. (gondolas can turn corners) followed Harrison over I-5 and ended at Harrison and Westlake in SLU. This would link to niehborhoods that are separated by the freeway and provide a way for link riders from the north to get to SLU. If you run the gondola down existing streets and at a lower hieght (under 50 feet of the ground) you would avoid huge stations, problems with “air rights” and existing fire department ladder trucks could evacuate people from the cars in an emergency.
Start small and simple. Prove the technology, then build from there.
-Thoughts?
Some stats on speed and capacity:
The fastest aerial trams in North America run at 2,000 feet per minute.
The fastest gondola in North America is the Peak 2 Peak at Whistler, which runs at 1,476 feet per minute. Most smaller gondolas run at 1,000-1,200 feet per minute.
The highest capacity gondola in North America is at Mammoth Mountain, California. It moves 3,600 people per hour, per direction in 15 passenger cabins with a 15 second interval between cabins. There are four other gondolas in North America that move 3,000+ passengers per hour per direction.
The highest capacity aerial tram is at Stone Mountain, Georgia. It moves only 1,280 people per hour per direction. Even 4 and 6 passenger gondolas have higher capacities than any aerial tram.
The Portland Aerial Tramway is an effective point-to-point transit connection between a multi-modal station (streetcar, future LRT?, with great TOD) and a mountaintop medical center. Incredible views. The bicyclists like to bring their bikes up on this and then cruise down.
http://www.portlandtram.org/
I-5 is a tremendous barrier between Capitol Hill and Cascade. Glenn MacGilvra was always pitching a “bridge over the River I” in this area in the 90s. A bridge and elevator might make more sense than an aerial tram. You really want great connections with a point-to-point shuttle. Broadway and Westlake are too far I think. Now if there were LRT on Fairview or Eastlake…
“This is not the case with gondolas which have cabs that are able to detach from the continuously moving propulsion cable. This means that there can be multiple stations, with station located anywhere along the line.”
But doing so is *horrendously inefficient* and only works for small volumes of passengers, which you *didn’t* mention.
There is a serious problem where a single gondola with slow entering / slow exiting passengers causes a bunchup on the line. At the termini, this can be handled partly because every gondola is emptied, and partly because a large staging area for gondolas is provided. Providing this “parking area” for every intermediate station bloats them substantially.
This is fine on a low-volume ski lift (though in fact most of those do *not* do this) but it’s no good for urban transportation. There are a couple of gondolas in South America which have one intermediate stop with low passenger volume, none with high passenger volume.
The attachment-detachment process for gondolas also creates a major safety hazard. A very common sort of gondola has a secondary carrier wire to which the gondola is permanently attached; if you have this sort, intermediate stations are really not viable at all.
If you have the other sort, single-wire gondolas, intermediate stations are LARGE and COMPLICATED in order to make them safe.
There is a reason why gondolas are used almost entirely for point-to-point transport; they’re terrible for intermediate stations.
Some interesting news about TransLink’s defunct aerial tramway proposal.
http://www.railforthevalley.com/latest-news/zweisystem/sfu-gondola-update-ah-the-real-story-emerges/