Aerial Trams



Aerial Technologies, Lesson 5: Aerial Trams

The Portland Aerial Tram. Image by functoruser at flickr.

Aerial Trams are the granddaddies of cable transit. They’re big, they’re aggressive and what they do, they do really well. Problem is, they can’t do much. They’re a completely antiquated technology due to their lack of detachability.

Like BDG or 3S systems, Aerial Trams use one or two stationary ropes for support while a second or third moving rope provides the propulsion. But unlike BDG and 3S systems the Aerial Tram’s grip is fixed and cannot be decoupled from the propulsion rope during operations. This means that corners are all but impossible in an Aerial Tram configuration and intermediary stations are limited to single mid-points along the line. These mid-stations are incredibly rare. Read more

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Bondada-Neumann Study, Part 2

(This is Part 2 of a 2-Part piece on the Bondada-Neumann Study from the late 1980’s. In Part 1, I focused on the issue of Familiarity. In Part 2, I discuss the differences in perceptions between planners with cable experience and those without.)

Bondada and Neumann’s discovery that transit planners and engineers had little familiarity with cable propelled transit technology is not much of a surprise. It’s a little bit like discovering that most college freshmen know very little about quantum physics. It’s such an on-the-nose observation, it’s basically a non-discovery.

In the second half of the Bondada-Neumann study, however, real insight was gained.

On average, planners and engineers knew little about cable. But that was on average. Looking at discreet individual responses, however, Bondada and Neumann noticed that a 24% minority of respondents had significant experience with cable whereas the 76% majority had virtually no experience with cable. As such, the pair analyzed their data according to those two different cohorts.

Respondents were asked to rate on a scale of 1 to 10 (1o being more favourable) aerial tramways and gondolas based upon 32 different physical characteristics. These included such things as operating and capital costs, procurement process, headways, accessibility, etc. The results were overwhelming.

For each and every one of the 32 physical characteristics, the respondents with cable experience rated cable higher on the scale than the respondents with absolutely no cable experience whatsoever. Every single time.

What’s more, the difference was not slight. Those with cable experience gave cable scores 1.5 – 3.3 points greater than those with no cable experience. The average was 1.7 points, which on a scale of 10 is more than statistically significant. It’s a huge difference. To draw a loose analogy, it’s the difference between having a university essay graded B+ or C-. Now imagine the C- scores were being given by a professor who knew absolutely nothing about the subject the essays covered.

You see the problem immediately.

The implications of this study are still felt today. The vast majority of planners and engineers know little or nothing about cable transit. Those that do, view it favorably while those that don’t, view it less so. Bondada and Neumann suggest that as the majority of planners have no experience with cable, they may not even include it in an alternatives analysis thinking (incorrectly) that it is poorly suited to the needs of public transit.

It’s similar to being in a restaurant (please excuse the second analogy).

Imagine you’re trying to decide between two specials: A chicken and a fish. Problem is, only one out of the restaurant’s four servers have tried the night’s fish special. She thinks it’s great, but what if you’re not sitting in her section?

What if you’re sitting in one of the three other servers sections? They all have tried the night’s chicken special but not the fish. What happens then? What happens when you ask How’s the fish? What’s he going to say? You know exactly what he’s going to say. He’s going to hedge his bets. He’s going to say It’s okay. It’s fine. I don’t know but one of the other servers says its good.

But he’s not going to rave because he doesn’t know. He’d probably be happier if you forgot about the fish altogether. In fact, you probably wouldn’t even know there is a fish special because he didn’t even bother mentioning it in the first place. Why bother mentioning something he knows nothing about? Problem is, you really like fish but you were never even given the chance to choose.

Chicken it is then.

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Bondada-Neumann Study, Part 1

(This is Part 1 of a 2-Part piece on the Bondada-Neumann Study from the late 1980’s. In Part 1, I focus on the issue of Familiarity. In Part 2, I’ll discuss the differences in perceptions between planners with cable experience and those without.)

In the late 1980’s two civil engineers from West Virginia University (WVU) had a theory. Murthy Bondada and Edward S. Neumann guessed that a lack of familiarity with cable transit among engineers and planners was holding back cable’s use in urban environments.

The pair created a mailback survey designed to measure not the quality of cable transit itself, but rather the perceptions planners and engineers had of the technology’s relative worth within a group of seven different transportation technologies: Passenger buses, passenger vans, self-propelled people movers, personal rapid transit (PRT), cable-propelled people movers, aerial tramways and aerial gondolas.

Firstly, Bondada and Neumann sought to discover how familiar transit planners and engineers were with cable transit. Planners and engineers were asked to rank their familiarity of the seven technologies along a five point scale from Very High to Very Low. How familiar were they with cable? In short, not very. Of the seven technologies, cable-propelled people movers, aerial tramways and aerial gondolas were ranked 5th, 6th and 7th respectively.

That could hardly be surprising. Even today, cable transit is little more than a triviality to the planning community but at least we now have tools like the internet (and this website!) to help people learn more. Not so in the neon-hypercolored glow of the 1980’s.

There were, however, two truly surprising results of the familiarity survey.

In the 1980’s cable-propelled people movers were incredibly rare. If you were planning on building an automated people mover, you were likely to use self-propelled technology. Aerial gondolas and tramways, however, had been implemented in ski resorts and cities around the world. The difference in relative familiarity between cable-propelled people movers, gondolas and aerial tramways was statistically minor, but even still: Why had the rare cable-propelled people movers ranked higher than common tramways and gondolas?

While Bondada and Neumann never answer this question explicitly, I suspect the answer lies with the fact that a cable-propelled people mover simply looks more like the “traditional” (ie: train-like) transit technologies we’re used to. Aerial cable systems must have just looked too weird to the survey’s respondents.

The more you look at the Bondada-Neumann study, the more bizarre things get. Of all seven technologies included in the study six were actual, real-world technologies. Only one – personal rapid transit – was theoretical. The technology had never been built and even though a people mover system at West Virginia University (the school Bondada and Neumann hailed from) had been dubbed “Personal Rapid Transit” it was not.

And yet – in rather stunning irony – respondents to the familiarity survey ranked PRT technology 4th by a healthy margin over all cable technologies despite having never been implemented anywhere in the world.

This was quite shocking. One expects a travel agent to be more familiar with Rio than Atlantis; an archeologist more aware of King Tut’s Mask than the Holy Grail; or an equestrian to have more experience riding Zebras than Unicorns. But not in this case. Here was an entirely illogical result. The planners and engineers in the study had demonstrated more familiarity (or at least a willingness to admit more familiarity) with a mythical/theoretical technology than three other technologies that had been successfully implemented worldwide.

If ever there was a case that showed just how subjective our transit planning system and regime was, this was it. But what Bondada and Neumann discovered next was equally (if not more) surprising.

(Click here to read Part 2 where I discuss what Bondada and Neumann discovered about the differences in perceptions between planners with cable experience and those without.)

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The Peak 2 Peak (Part 3)


Image by Steven Dale

Last month I toured Whistler’s Peak 2 Peak cable gondola system. This is Part 3 of a 3-part series on the system. Click on the following links to view Part 1 and Part 2.

Most aerial cable systems offer a smooth ride. What little friction there is, is rarely felt by the rider. Except, of course, when it comes to passing over towers. When passing over the sheave assemblies attached to these towers, riders tend to feel a noticeable bumpiness and accompanying noise. To some, it can be slightly unnerving. The older and more basic the system, the more pronounced this is.

The Peak 2 Peak’s 3S technology does away with these nuisances. When passing over the towers, there is virtually no change in noise level nor smoothness of ride. The engineers should be commended for this feat. Not only does it make the ride more pleasant, it makes the technology more palatable to the psychological fears of riders not accustomed to cable technologies.

The towers are, however, quite large compared to less advanced systems. This is partly due to the technology in question but also partly due to the distance between towers. At it’s most extreme, 3 km of ropes, vehicles and skiers are supported by only two intermediary towers. It’s an engineering marvel, but means the towers are giants. The four intermediary towers range between 35 to 65 metres in height!

(Such tower heights would be too large for an urban environment unless extreme design changes are made. Granted, I can think of only a few urban situations where a 3 km towerless span would be required.)

As I said earlier, everything about the Peak 2 Peak feels oversized and enormous. Use whatever superlative you like, it probably applies to the Peak 2 Peak.

Except when it comes to the engine.

I’ve seen my fair share of cable transit engine rooms and they’re almost always underwhelming. One sees these massive systems and one expects a corresponding engine room. That expectation almost never meets reality. The Peak 2 Peak is no different.


Peak 2 Peak Main Engine Room. Image by Steven Dale

The Peak 2 Peak’s main engine and drive is located beneath the station in a bland, white subterranean room. The sound of the engine is deafening, but the engine itself is nothing much to behold. Despite it’s fire engine red coat of paint, the machine is unassuming. It’s small enough to fit inside a streetcar with room to spare for a half dozen riders and their backpacks.

That this piece of equipment moves 18 km’s of steel cable, 28 vehicles, 4,100 passengers and a steel bullwheel is remarkable. In fact, it’s almost unbelievable. What’s even more unbelievable is the diesel backup engine. The back-up is less than half the size of the main drive but can switch on within seconds of a main engine failure.

Redundancy is the name of the game here.

Of course the engine doesn’t do all the work. Gravity does much of it. The “belly” (I love that term) or sag of the rope is significant, on the order of three or four hundred metres. As maintenance engineer Sean Duff explained to me, the belly of the rope allows the system to capture potential energy (gravity) and use it to its advantage. Vehicles descending the belly pull vehicles up the belly. The engine only has to provide enough energy to compensate for the difference.

According to Sean, it’s an incredibly efficient system.

Because the Peak 2 Peak is a horizontal system, Sean explained, the system actually uses less energy than do the other gondolas on Whistler Mountain. Whereas the other systems must typically drag hundreds of people up the hill (with very few people using the system to descend the hill), the Peak 2 Peak has a relatively constant load on both directions. This causes a counterbalancing effect which reduces energy consumption.

When, however, a system with more “vertical rise” has more people descending the lift than ascending, it’s not uncommon for engineers to witness energy consumption drop below zero. That is, the system is basically generating energy because the weight of the descending line is heavier than the weight of the ascending line.


Image by Steven Dale

It’s refreshing how accessible the system’s engineers and maintenance staff are. Part of that accessibility is due to their presence. Unlike other transit technologies, cable systems tend to have engineers and maintenance staff onsite at all times of operation. As more-and-more cable systems demand near round-the-clock service (especially in airports), long shut downs for maintenance are just not a possibility.

This has caused the cable industry to adopt a policy of preventative maintenance. Throughout the course of their workdays, cable engineers are not fixing problems after the fact, they’re preventing them from happening in the first place.

As I said in Part 1 of this series, I doubt the Peak 2 Peak was really meant for skiers. Skiers want to go from the top of a mountain to the bottom, not from the top of one mountain directly to the top of another.  But that’s not really the point of the Peak 2 Peak.

Instead, the Peak 2 Peak is a statement of cable’s advances. Is it necessary? No. Is it overkill? Completely. But at a total cost of only $57 million, this overkill is still more cost-effective and deeply efficient compared to our traditional transit solutions.

It may be at a ski resort, but it’s transit through and through.

Return to Part 2.

Return to Part 1.

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The Peak 2 Peak (Part 2)

Image by Steven Dale

Last month I toured Whistler’s Peak 2 Peak cable gondola system. This is Part 2 of a 3-part series on the system. Click on the following link to view Part 1.

The very first thing one notices about the Peak 2 Peak is the sheer scale of it. Everything is bigger, flashier and a little less . . . quaint. This quaintness of past cable systems, I suspect, has caused much of the resistance to the concept of cable transit. Too small, too slow, etc.

None of that exists with the Peak 2 Peak. Signs in the vehicles proclaim the system’s high speed, large vehicle size and hefty system capacity. The Peak 2 Peak is big and it wants you to know it. It’s an obvious volley by the cable industry that says “we’re transit, too.”

Unfortunately, the scale of the system sometimes works against those goals. Stations are enormous and far too big for most urban areas. In cities, land is at a premium and extra space costs both current dollars and future tax revenue, a double negative in the minds of public transit agencies who might consider the technology.

This is not, however, an entirely fair assessment. When one examines the drive machinery, one notices that it is not significantly larger than standard systems. It’s a question of divorcing the infrastructure from the architecture. The infrastructure is standard and (relatively) modest, whereas the architecture is gargantuan.

This architecture is, however, necessary. The Peak 2 Peak has only two stations and these stations double as maintenance and parking facilities for each of the 28 (and 2 backup) vehicles. Public transit agencies also possess vehicle maintenance and parking facilities, but those are generally off-site and out-of-mind.

Off-site maintenance yards are, however, very expensive and create additional operating costs by way of the costs involved in bringing vehicles from the yards into revenue service. Are those costs off-set by locating the yards in low-cost industrial areas? I don’t know. What savings would accrue (if any) from having vehicles maintained and stored on-site instead of off-site would be an interesting discussion, but is a bigger issue for another time.

Incidentally, the next 3S system to be opened in the world will be a flat, temporary urban system in Koblenz, Germany. From the renderings I’ve seen, it appears the system will utilize slim-profile stations. How that system integrates maintenance and operations facilities into the whole will be useful to see and should contribute much to this conversation. There are, after all, more fingers on your hand than there are 3s systems in the world.


Vehicles are colour-coded to indicate those that have glass-bottomed floors (silver) and those that do not (red). Image by Steven Dale.

While the design of the system as a whole is utilitarian and industrial, there are a few neat flourishes.

Firstly, the seating is actually comfortable. Unlike most ski lifts, these are seats one could imagine spending 30 minutes sitting on. Are they perfect? Not by a long shot, but they’re a vast improvement over existing cable seats.

More important, the ratio between seats and standing space is excellent; 22 seats compared to 6 standing spaces per vehicle. Interestingly, however, I observed almost no one sitting. Most were happy to roam about the cabin, taking in the sites. These cabins are large, remember, and roaming is just about the best word to describe the way riders float around the cars looking through the windows.

The windows are also worth commenting on. Most ski lift gondolas utilize moulded plexiglass. Plastic windows add a cheapness to most gondolas, and are easily keyed and scratchittied (yes, that’s actually a word) by vandal-riders. Not so with the Peak 2 Peak. All vehicles are equipped with clear, tempered glass windows. The heft of these windows add so much to the experience it’s hard to describe.

It’s like the difference between cheap Ikea wine goblets, and fine crystal. Why one is better than the other is hard to quantify, but the difference is there and everyone notices it. The simple act of using glass windows instead of plastic transforms the Peak 2 Peak from just another gondola to something that approaches what we understand as transit.

And while speaking of glass . . .

Two of the 28 vehicles have a glass-bottomed floor. These floors give the rider an unprecedented and unique view of the world through transit. While I might be wrong, I suspect there is no other transit technology in the world that allows riders to look down upon the world from a height of almost half a kilometre.

The view of Fitzsimmons Creek from a height of 436 m. Image by Steven Dale.

This window is, however, cordoned off. Riders are not allowed to stand upon the glass floor, though the rails forbidding this are such that any person who wanted to, could. It’s nothing more than a psychological safety mechanism. It doesn’t make anyone more or less safe, but it makes you feel more safe. The tradeoff, however, is a loss of 2-6 spaces for standees, negligible in a resort area.

One of the most wonderful design novelties of this systems is the way in which glass-bottomed vehicles are identified. Whereas all the normal vehicles are painted red, the two glass-bottomed vehicles are painted silver. There is a beautiful elegance to this design feature. Instead of reading words (which you may not understand if you’re a tourist) or looking into each vehicle as it passes, you simply need look at the colour.

Colour is a powerful tool that is rarely used by transit agencies. Individual routes on a map may be colour-coded, but the vehicles themselves rarely are. Instead, transit agencies rely solely on numbers and names to differentiate their routes.

Why not paint vehicles different colours to suggest different features, or routes? It makes almost perfect sense when one considers it.

From an overall design perspective, the Peak 2 Peak is not aesthetically beautiful. It does, however, offer so many small, practical features it’s hard not view it with fondness. It is a clear and definite step in the right direction.

Proceed to Part 3 where I’ll wrap up this series with a discussion about the engineering and electricity demands that are put upon the Peak 2 Peak.

Return to Part 1.

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The Peak 2 Peak (Part 1)

Image by Steven Dale.

Last month I toured Whistler’s Peak 2 Peak cable gondola system. This is a 3-part series on the system. Part 1 is necessarily technical in nature and will refer back to several pages of The Gondola Project for those unfamiliar with cable technology.

With small, incremental baby-steps, cable transit continues to push its capabilities beyond what people traditionally expect of it.

Whistler, British Columbia’s Peak 2 Peak, however, is not so much incremental as it is an innovative leap forward for the technology. One of my former university professors, after having ridden the system, described it to me as an “incredibly impressive machine.”

(Somehow referring to it simply as “a machine” doesn’t quite do it justice, but that professor was never easily impressed anyways.)

The Peak 2 Peak was initially conceived by the proprietor’s of the Whistler-Blackcomb ski resort as a method of shuttling skiers and hikers between the tops of the resorts two major mountains (Whistler and Blackcomb).

You can’t help but question the logic of this: Skiers (the primary users of this system) use a gondola to get up a mountain so that they can ski down the mountain. As both the Whistler and Blackcomb Mountains each have their own gondola systems, why would a skier need to use the Peak 2 Peak at all?

Nevertheless, the novelty of the system attracts strong ridership and since it’s opening in early 2009, the Peak 2 Peak has become an attraction in it of itself.

At it’s highest point, the cable is 436 m above the valley floor, which (for comparison) is about the height of Chicago’s Sears Tower. And yet there’s virtually no vertical rise. The Peak 2 Peak is an almost completely horizontal system.

The Peak 2 Peak experiences virtually no vertical rise from station to station. Image by Steven Dale.

While the height of the system is impressive, it’s the valley crossing that garners most attention. While most cable systems would require several intermediary towers to accomplish a 3 km long valley crossing, the Peak 2 Peak does so without a single intermediary tower. This is the longest unsupported cable span in the world and the Peak 2 Peak owes its fame to this very feature.

Massive, unsupported spans such as this were impossible before the recent 3S innovation. Much like the technology behind Innsbruck’s Hungerburgbahn, 3S technology is a hybrid fusion of two separate cable technologies. But while the Hungerburgbahn fused funiculars and gondolas, the 3S is a hybrid of aerial trams and gondolas.

Aerial trams have a high speed, excellent wind stability and large vehicles. They are also expensive. The Portland Aerial Tram and the Roosevelt Island Tram are two very good examples of this technology. The trouble with aerial trams is they are not detachable systems and that causes their overall capacity to decrease. Corner-turning is impossible. It’s a high-cost, low-value technology.

Gondolas, meanwhile, have modest speeds, smaller vehicles and modest wind stability, but are detachable. This detachability increases system capacity, lowers wait times and allows for corner-turning.

The 3S, therefore fuses the benefits of both technologies while eliminating the deficiencies of each. The Peak 2 Peak runs on two individual and stationary support cables while it is propelled by a third separate moving cable. It is basically like a Bicable system with a second support cable. This second support cable allows 3S technology to carry vehicles of up to 35 people and operate safely in 100 km/hr winds.

Capacity of the Peak 2 Peak is 2,500 pphpd with 28-person vehicle headways of 49 seconds. Even shorter headways and larger vehicles are possible, driving the capacity of a 3S system above the 4,000 pphpd threshold.

Two stationary "track" cables with the moving propulsion cable in the centre. Image by Steven Dale.

While the Peak 2 Peak does not utilize intermediary stations or corners, those two features are both possible with 3S technology and are sure to be realized in the future. As of yet, however, only a handful of 3S systems are operational across the globe.

Proceed to Part 2 where I discuss station and vehicle design and footprint.

Click here to read Part 3

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Roosevelt Island Tram

New York’s famous Roosevelt Island Tram will be closing this spring for a complete overhaul. The system, built in the late 70’s is one of the few public CPT systems in North America and recently became fully-integrated into that city’s transit system. So if any of you are in NY in the next month, take the time to check out what is a truly unique system. It’s well worth it.

If you don’t have the chance, the wonderful video below should give you an idea of what it’s like.

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