 Everyone loves to hate or at least joke about gadget bonds. But I do think it's interesting that when you look at all the gadget bonds out there, it seems like either every other one is French or uses rubber tires. Or is French and uses rubber tires. But how do these technologies work? Why do they exist? Do they actually provide any benefits? Or that age-old question, should rubber-tired trains and trams simply be banished to transit history? Let's find out. If you're not already, consider supporting the channel on Patreon for behind the scenes, early access to videos, and other benefits. One cannot talk about rubber-tired trains, yes, trains with rubber tires, without talking about French metro systems, most notably the Paris Metro, which originated the idea of rubber-tired metros. But that's not to say that rubber-tired rail transit is only of French origin, that's definitely not the case. There are all kinds of rubber-tired rail systems out there, from straddle beam monorails that originated in Germany and have gained particular popularity in Japan, to rubber-tired automated people movers from companies like Westinghouse that are now under control of Alstom, and which serves airports all over the world, as well as Singapore as an LRT. That being said, in France, I think you generally find the widest variety and highest capacity rubber-tired transit systems. And as mentioned before, they really originated and had their greatest moment as part of the Paris Metro, which experimented with retrofitting some of its existing lines with rubber tires in the mid-20th century, in a bid to improve performance. Indeed, as with the other Paris-derived rubber-tired metro systems from Montreal to Mexico City to Santiago de la Zan, this means that the rubber-tired technology is really more of an overlay to existing steel-wheeled metro technology than its own independent thing. And these systems still contain steel wheels, steel rails, and conventional railway switches, which sit inside of the rubber tires and the concrete or steel railways that they operate on. In Paris's case, that meant that many of the lines that were retrofitted to use rubber tires weren't actually designed to use rubber tires from the get-go, and that means they couldn't fully take advantage of the technology. This wasn't really the case for the exported systems or Line 14 in Paris, which is much newer. Now, those steel wheels on the trains actually do form an integral part of the operation, as they're actually used for braking. That being said, while the system is operating optimally and not traveling through switches, these steel wheels don't actually make contact with the rails, and they're suspended above them via the rubber tires. The steel wheels contact with the switches when the trains travel through switches is only made possible by extra long wheel flanges, which these types of trains have. All of this brings us to a common problem we'll see with a lot of these rubber tire transit systems, which is how do you get power if you're sitting on a bunch of insulators? The answer in this case is via guidebars that sit on either side of the running rails. These guidebars are rolled along by other horizontally mounted tires, and also is where power is picked up from. They also, given their name of guidebars, are used to guide the bogies through corners. But the Paris Metro Tech is not the only rubber-tired French Metro technology. There's also VAL, which was originally developed for use on the Metro in Lyon. VAL has come to stand for Light Automated Vehicles, and the technology has been exported quite successfully. These French gadget bond systems are only systems we're really talking about because they were fairly successful in being exported to lots of other places around the world. And VAL in particular has been used both on metros and on a lot of automated people-mover airport-type things. Now, the choice to use rubber tires on VAL has a few reasonable explanations. For one, the low slip of the tires on the guideway can be really useful for driverless operations, which all VAL systems use. That's because understanding where the train is located, as well as dealing with things like platform screen doors, is easier when you have wheels that don't easily move independently of the vehicles themselves, which is possible with steel wheels since they can slip and slide. The small trains and rapid acceleration enabled by the tires also allow VAL trains to travel incredibly close together, as little as one minute apart. They're also useful for steep grades and tight corners, which along with the very small coaches used on the system makes it highly maneuverable and thus highly flexible. For power and regular running, the VAL system isn't actually that different from the Paris Metro rubber tire technology in that there are rollways and guide bars which provide power. But the wheel sets are much simpler on VAL and that's in part because the vehicles are so much lighter and thus can be supported by only four tires, making them much more like a guided automated bus and less like a train since there aren't actually bogies or steel rails. That being said, there is a slot-like rail that does exist through switches that allows trains to be guided through them. Original VAL has been used in a number of systems around the world, usually in small, low-capacity configurations. These include Lille, Ren, Toulouse, as well as on the Charles de Gaulle and Orly Airport People Mover systems. And also in Taipei, I haven't explained her about Taipei, but let's just say there was quite the showdown with Bombardier who built trains for the otherwise proprietary system. Interestingly, Siemens, who actually acquired the VAL technology, has been developing a new VAL technology for use in cities like Ren. And it's known as NeoVAL and it's essentially meant to supersede the original VAL technology. In this case, the NeoVAL system essentially further simplifies traditional VAL by adding a central metal guidance rail, something Siemens was able to do in collaboration with Lore Industries, creator of the very much infamous Trans Lore system. So what is Trans Lore? Well, it's a rubber-tired tram technology that in many ways resembles a guided bus, but cannot actually be steered like a bus and instead relies on a central steel guidance rail, pretty much the exact same as what you see on the NeoVAL. Since it runs on rubber tires, again like a lot of these technologies, and has a central steel guidance rail which you can use to return current, it also operates using a single wire overhead and a pantograph. Now, Trans Lore vehicles do look mostly like trams, but because of the proprietary design and unusual setup, cities which have installed the technology have basically been stuck with a single vendor, since these aren't standard tram vehicles. The systems have also faced a number of derailment and railway degradation issues, because unlike with a standard bus, if you have a guided bus, which let's be honest, is what Trans Lore is, your wheels stay in the same place as your rolling ups been down all the time, and that tends to lead to the wearing of grooves in standard asphalt. So you need expensive, concrete railways that basically obviate any cost savings the technology would give you. Despite these issues, the technology was somehow unsurprisingly used on two Paris tram lines, as well as in Venice and Padova in Italy, and it was actually exported outside of Europe to China, as well as a few other cities. From Trans Lore, we moved to an even more unusual and seldom used technology. The Bombardier GLT, not Bombardier's greatest moment, and they had a few not great moments. This technology was only used in two systems, and in some ways it's like Trans Lore, since it used a central guidance rail, and one of the two systems used a single overhead wire with pantograph. Now, fortunately, unlike Trans Lore, it was able to operate as a standard bus when it went off rail. But unfortunately, it went off rail a lot of the time, when it was on the rail, because the technology has really horrible derailment issues, which required really draconian speed restrictions on GLT systems, only one of which is remaining, because one of the cities got so fed up that it ripped it out and replaced it with a standard tram. Unfortunately, as with Trans Lore, GLT was also proprietary and non-standard, which meant getting replacement vehicles and parts was difficult. And in a super weird case, one of the systems actually didn't have a maintenance facility on the electrified route, and so the buses had to drive to the separate bus maintenance facility for maintenance. And because this system didn't have trolley bus lines or anything like that, every GLT vehicle had a diesel generator on it, which is kind of strange. Now, when assessing all of these technologies, I think it's important to acknowledge that to some extent, they all do have some benefit. In some cases more, and in other cases less, much less. Anyways, it's important to try to understand those features when trying to assess whether this technology is good in any particular circumstance. Most technologies, even the super weird ones, will make sense in some extremely niche cases. The broader question is why we don't use these technologies in every city and town. I also have to acknowledge that external factors probably also played a role. One of the first Trans Lore systems was built in the town that is home to one of the world's largest tire manufacturers. Now, since we've talked about all of the different systems, let's talk about some potential benefits of rubber-tired rail transit. For one, as I've mentioned quite a few times, these systems can quite effectively climb steep hills, and that can be useful. While steel wheel traction has come a long way in the decade since these technologies were originally created, ultimately in extreme cases rubber tires probably are better. In the case of Medellin, for example in Colombia, the Trans Lore line they built runs up an incredibly hilly slope, and using standard trams would probably not be advisable. That being said, I don't necessarily think Trans Lore was the best choice. Was there really not a better alignment that could be chosen? Could they not have used buses? These are questions that I can't really answer but are worth considering. Ultimately, in this case, Trans Lore does kind of do what it's supposed to do, even if it is a rough, uncomfortable, not really tram-like ride. Now, rubber tires can also broadly reduce vibration because tires are soft and so less vibration transfer happens from the vehicle itself into tunnels and guideways. The softness of rubber tires and the general higher flexibility of these systems also probably mean that they work better in poorly maintained or uneven situations where the rollway is kind of in rough shape. That's not necessarily fully a benefit though because anything that encourages you to not maintain your infrastructure is kind of bad. Of course, the grippiness can also help with service frequency and things like alignment with platform screen doors, though as with a lot of the benefits of rubber tire technology, that has been mostly obviated by better steel wheel technology in the past couple of decades. One feature that does come up a lot is that rubber tires are unlikely to last as long as steel wheels and since they aren't made out of steel, they're just inflatable bits of rubber, they can't be reprofiled like steel wheels to keep them running for longer and longer. That being said, swapping out a tire for a brand new nice one is possible and there are potentially arguments that tires could be good when you have a small operation with something like, say, a people mover. That being said, for a metro system, I think the ride quality and benefits of steel wheels probably outweigh any convenience of being able to easily swap tires. Now, sound is another potential benefit, at least for the guide bar using systems because the guide bars and overall guidance technology means that there's very little need for steel on-steel contact that leads to the horrible squealing you do here on some conventional metro systems, especially going around tight corners. But this can actually also be a negative and so now let's talk about some of the drawbacks. While these technologies are unlikely to lead to the kind of steel on-steel squealing you do here on some steel systems, what they do lead to is roaring, especially at high speeds. It's kind of like being in a car driving down a highway. There's just a loud, low roar and this is even worse because rubber-tired metros in particular have a lot of tires. At the same time, while tracks and rollways might work in rougher conditions, they still ultimately need regular rebuilding and maintenance. And since rubber-tired technology is non-standard, it's just a little more complicated and expensive. In the case of the tram systems, while they purportedly save cost by not using two rails and instead just using one rail, they still have most of the infrastructure of a tram. You've got the overhead line, you've got a single rail, you've got a concrete guideway, but you don't get the service quality and the ride quality of a tram. So it's sort of an 80% of the cost for 20% of the benefit sort of situation, except it's more like 100% of the cost. So it's just not a worthwhile technology to pursue. Please don't build a transfloor. Another issue is ride quality. And while it varies from system to system, and I will say, I don't find, for example, the Montreal Metro to be that much less comfortable to ride on than the Toronto subway, you still do get more bouncing and jostling, which is just the nature of riding on rubber tires, which are inflatable and kind of soft. Now, flat tires are generally unlikely, especially on the metro systems, because they're isolated from traffic and people who might try to throw tax on the track. That being said, they are possible, and a burst tire can cause some havoc for these systems. The Paris Metro tech in particular can operate on the steel wheels, but rubber tire fragments are a mess. And so not great. The benefits of the rubber tire technology can also go completely out the window in inclement weather, which is why Montreal and Sapporo, both snowy cities that use rubber tire technology keep their systems indoors at all costs, and that makes building out metro more expensive. It's also sort of a weird thing that we often take for granted that a metro system or a bus system will just mostly work in any weather. And so the idea that if it snows a bit, your metro might not work is kind of crazy. Ultimately, transit and specifically rail transit is all about standards. So while using a unique technology might make sense in a very, very niche and specific case, in far too many cases, gadget bonds get used because someone paid to develop them and now someone has to pay those costs and someone has to buy the systems. Even if a specialized technology can provide some unique benefits over traditional technologies, it's probably not worth using unless the issue is so specific to your situation that no other technology will do. In most cases, it's probably just not worth it. Thanks for watching.