 Transit is an industry that's often susceptible to trends, from bus rapid transit to automated metros and fair for you systems. To be clear, not all of these are bad all of the time, but they are all topics that have gone from practically no attention to massive attention overnight. And in many ways you could argue the same is true for various orbital light rail projects. From Stockholm to Washington DC to Paris, a surprising number of cities have created new light rail lines that are meant to take people downtown, but rather around the city. But then the question arises, what types of trips are these services actually meant for? And how do they relate to other circular rail services? From metro to mainline trains. Basically, is this a trend that your city should hop onto? Let's discuss. A good place to start here is with what kind of system I'm actually talking about. And I think one of the best examples of an orbital light rail line in the world is the Tvarbanen in Stockholm. An 18 kilometer light rail line which travels north south around Stockholm to the west of the city center, intercepting the various radial, metro and suburban rail lines. Key elements of the Tvarbanen service include the orbital or circumferential alignment that connected various destinations outside of the city center without needing to actually go into it, the reuse of old rail white infrastructure, including a portion of track that actually still sees some use with freight trains, the comparatively low cost of its construction and the interchanges with so many other rail services. Now, if you want to learn more specifically about the Tvarbanen, I talk about it more in my Stockholm Metro explainer video, so go check that out and then come back. In many ways, the tram link service in South London is actually similar to the Tvarbanen. The tram link forms part of a circle providing for journeys east west and south London. It also provides connections to various national rail and TFL rail services and it was built at a low cost and quite quickly thanks to the reuse of old and underused railways. In both cases, the use of light rail was critical because it allowed you to reuse existing rail corridors, many of which were not fully grade separated since they weren't heavily used, while at the same time being able to use street running or side of street running approaches to actually stitch together multiple separate rail quarters. Funnily enough, both the Tvarbanen and the tram link opened in the early 2000s as well, so they both kind of happened around the same time. After the late 20th century resurgence in trams that kind of started in France, you could also definitely make the case that the Maryland Purple Line, which will more or less act as a part of the Washington DC Metro system and will connect a bunch of different radial lines in Maryland, is also doing something similar, just more than 20 years later. Speaking of North America, you might even argue that the Eglinton Crosstown is one of these lines, which really highlights that what orbital looks like really depends on the geography of your region and the geography of your existing radial transit service. Basically, all of these are moderate capacity light rail lines, with street crossings and lots of stops, but with enough sections of fast running that they actually tend to provide a lot of bang for the buck, at least usually. So what actually distinguishes these orbital light rail schemes from other types of circular orbital or looping railways? Well probably the most noticeable thing is that these lines, despite being orbital, are rarely actually complete circles. T3 in Paris is almost there, but most of the rest aren't, and I think a lot of this has to do with trade-offs between cost, capacity, speed, and connectivity. First of all, such schemes rarely actually serve full cities. Generally they serve only a part of the circle, as in London. And they do seem particularly common in arc-shaped cities like Helsinki, Stockholm, Copenhagen, or even Toronto, where the city centers are on or quite close to a major body of water, and so a true looping rail line wouldn't make a ton of sense. Even in the case of London or Paris, making such a line into a full circle would rarely be seen as a top priority, since for many trips it would be faster to use conventional services to get into and then back out of the city. Paris has likely gotten closer than any other city to fully completing its orbital rail loop, and that's probably helped a lot by its high uniform density and the large number of neighborhood to neighborhood trips happening in central parts of Paris. There's also the issue of cost and capacity. If building a smaller project, it's likely easier to string together a good right-of-way out of existing disused or underused ones. But a bigger project makes this and the relatively low capacity of such a line a less exciting prospect. It would also probably take longer to build, which kind of gets rid of one of the main benefits of these orbital light rail services, which is that they can generally be built quite fast with little modification to existing infrastructure and corridors. So what types of trips can you actually serve with this type of line? Well, for one, the type of trip that travels along the circle that traditionally might have required someone to go into and back out of the city center or get on a busy and uncomfortable bus. You can also serve a lot of last mile connections. For example, someone who lives along the circle and wants to get to one of the various radial transit services could make a lot of use of one of these orbital lines, but so could someone who's traveling on one of those radial services, potentially from further out in the suburbs or from the city center. And who wants to get to a major destination that isn't on the traditional higher order transit network? Of course, circle lines can also provide for higher level regional trips that allow people to avoid the city center or leaving capacity there, as well as complete trips that use multiple rail lines. But for the orbital light rail lines, I'd really argue they're best suited to the first two tasks, last mile and cross town connections. So why are these orbital light rail lines so attractive that they've seemingly popped up in a ton of different cities? Well, for example, such a trip would often traditionally be made with a high capacity bus route. And as you see in places like Helsinki and Copenhagen, such circumferential bus routes often get really busy because there isn't a lot of transit that serves those trips. Thus, in those cities on what are often mainly low density suburban corridors, it makes a lot of sense to make the small upfront investment for a big quality of life improvement with light rail over buses. On the other hand, a last mile connection on a tram is unlikely to be overcrowded, especially because these lines tend to have so many connections that you're unlikely to be traveling more than a couple of stops to get to your final destination. Otherwise, you would have taken another radio line to get there. Lower capacity trams also tend to work fine because these routes aren't super fast thanks to the lower average speed of a tram versus a completely grade separated railway and the fact that there are lots of stops, as well as lower frequency that is just kind of normal when a route has some street crossings, at least relative to a metro service. The slight transportation limitations of these routes are actually sort of a benefit in disguise because light rail vehicles will be sufficient for capacity because the trips are unlikely to be attractive enough to draw riders from very far away. Of course, their popularity also probably has a lot to do with the fact that they can fairly inexpensively and fairly well serve the type of trip that is obvious to a lot of people. Loops, everyone loves them. And to be fair on a lot of cities, looping routes actually do have a lot of demand relative to service since so many transportation networks are focused on serving nine to five office commuters traveling to a city center, even if they do do other things to a lesser extent. That being said, circling back to the three types of trips that I think such lines are probably particularly good at serving, it's probably worth mentioning that the third type of trip, the one I said that these lines probably aren't the best for actually serving are also the ones that I think have the most potential for ridership increase. Once you're talking about the usefulness of an orbital route on the regional scale, you're probably talking about more potential riders and more potential connections than a tram line would be able to handle. And as it turns out, few of the European cities I keep mentioning that have orbital trams or are potentially building them don't already have or are currently building a new high capacity orbital line. For example, in Stockholm, a new orbital metro line is being constructed to provide for more orbital capacity that to var bonden is incredibly congested, but also to provide faster trips. Meanwhile in Paris line 15 is being built to provide even further out orbital capacity, even as the existing T three a and T three B tram routes circles the city for the most part and lines two and six of the metro also form a loop. Of course, London also has the overground which travels through South London and Copenhagen has the S Tog F line. So while a new orbital light rail line could be a really good low cost way of stringing together some existing corridors and provide a high quality in demand suburban service that likely don't have the capacity to provide for all of the orbital transportation needs of even a moderately large city and such a project is less likely to have transformative effects on a regional scale. With such a light rail line plugged into your highly radial network, all of your radial lines definitely become more valuable and you can make high quality tricks between them. But it just isn't the type of transformational high speed, high frequency service that completely transforms the way your network operates. So what's the solution then? Well, obviously in a lot of places, these orbital light rail lines make a ton of sense, especially where they can be built quickly and cheaply using a lot of existing right of way as well as taking some street space and the like. But a project like the purple line in Maryland or even the Eglinton Crosstown in Toronto makes me wonder how transferable this model of an orbital light rail service is to places where transit just isn't all that cheap to construct, at least on existing corridors. Because if you followed the purple line or the Eglinton Crosstown, you'll know neither of these projects is being built particularly quickly or particularly inexpensively. And in that, they sort of miss some of the main benefits of the orbital light rail seen in Europe. And so they might be better off as something entirely different. To compare, the original parts of the far bond cost around 20 million US dollars per kilometer, whereas the Eglinton Crosstown or purple line are easily 10 times as expensive if not more. And a big part of that is spending money on tunnels or elevated guideways, in part to try to provide some sort of higher capacity and faster service and in some cases to avoid taking away space from drivers or landowners or even just messing with existing streetscapes in cities that would rather not be bothered. I think for cities like this Taipei, which I also covered in a previous video, might actually provide a really good example of what to aim for. At least for cities like Toronto and Washington, where projects of this scale are inevitably going to be very expensive and timely, and so you might as well go the extra mile and get something with way more transportation benefit. For example, Taipei's circular line or yellow line is a metro, but one which is lower capacity than the rest of its radio metro services, making it less expensive. And large parts of it are built over ground, and the benefit here is that like with the Orville light rail services, you can take advantage of the existing corridors to construct such a line. Instead of putting tracks right on the ground level, you can actually elevate the rail line, creating grade separation by default, since it's elevated, but also doing things like enabling new cycling connections and greenways underneath the guideway. This type of solution could work really well in suburban areas that have a lot of space, and while Taipei's circular line isn't exactly in suburban areas, something like the RAM definitely is. At the same time, the small trains running automated are the best of both worlds, at least for big cities where you're making this type of investment, since you can get both the lower cost of construction of smaller stations and other facilities, but also with the better service that can lead to more regional transportation impacts. Ultimately though, getting beyond the dollars and cents, such a line is always really exciting, because it offers high-quality transit that isn't focused on downtown workers. Not only is this the type of transit that needs more attention post-COVID, but it's also the type that's great for going to that restaurant you love across town, or going to an event with friends, and we could all use more of that. Thanks for watching.