Modes Series - Rapid Transit

The streets are bustling and filled with traffic. The city is growing and is projected to grow even further. Travel times grow longer and longer as surface routes get slowed down by clogged intersections and packed roads. There is but one solution - grade separate. Build either above the streets, or below.

While the terms have been repurposed or see use outside of their standard definition, Rapid Transit/Metro systems are the gold standard for high capacity urban transportation. They have three main characteristics - high capacity, high speed, and high frequency. At least high speed and one other of these (usually frequency) must be necessary to warrant investment into Rapid Transit.

For high capacity, it is necessary to have vehicles that are able to meet demand. This means vehicles much larger than any bus can reasonably hold. Some systems are built with the other two characteristics being more important - we will discuss these Medium Capacity Rail Transit/Light Metro systems in a later blog post. Most rapid transit lines boast vehicles with three or more units, each of which is somewhere around 42.7-75 ft/13-23 m long. Excluding light metros, the lower bound is closer to 47.3 ft/14.4 m (such as in Paris).

For high speed, it is necessary for stations to be spread far apart enough for vehicles to accelerate to max speed without interruptions. This means a dedicated right of way is necessary - if the vehicle gets stuck in traffic or has to slow down for any reason, it is not able to reach and maintain a high speed.

For frequency, it is necessary for vehicles to be able to show up at such a pace that a passenger does not need a timetable or even need to look at the time. They can expect to show up and go. Operationally, this is incredibly expensive, and to maintain the associated reliability of the headways, the infrastructure must be built with high frequency in mind. This means that grade crossings, even protected ones with vehicle priority, are not allowed except on peripheral parts of the network where there is little traffic. And even then, having grade crossings is not recommended for other reasons (e.g. makes full automation more difficult to achieve).

Of course, although these three things characterize rapid transit, something else is necessary to build such a network - passenger demand. As a high capacity transportation solution, rapid transit thrives in urban areas with stations located in locations of high passenger demand. Without the demand, there is no need for the capacity or frequency of rapid transit.

The first attempts at rapid transit all involved vehicles separated from the busy streets above or below. By taking suburban lines, interurbans, or trams/streetcars and putting them onto a grade separated right of way, they no longer needed to compete with street vehicles or traffic in the busy downtowns.

Many of these old lines were initially constructed for steam railways, and many no longer exist. The Liverpool Overhead Railway opened in 1893 and was the first electric elevated rapid transit line in the world, lasting until 1956. The first elevated railway in New York City, the Ninth Avenue Elevated, opened in 1868 as a steam railway and was converted to electric operation in 1902. The majority of the line was shut down in 1940.

Other older lines still thrive today, especially those built underground. The City and South London Railway opened in 1890 and still operates today as part of the London Underground Northern Line. The first line of the Budapest Metro opened in 1896 and still operates today.

But we digress - the focus of this blog is on the characteristics of the mode. However, despite us saying that, countless rapid transit systems are either hybrid systems or are simply rapid transit corridors part of another mode - something we will cover soon.

So what defines a rapid transit line? Despite the criteria, it's nearly impossible to come up with a clean definition. Over the years, all kinds of interesting and unusual lines have been classified as rapid transit in some form. We'll break these out into three sections - lines that are definitely and undisputedly rapid transit (or light metro), lines that break some of the guidelines, and lines that meet most of the guidelines but aren't considered rapid transit - at least on this website. The latter two sections will form natural transitions to future blog posts in this series.

Let's start with the systems that are generally considered to be complete rapid transit systems.

In the United States, the most iconic system that comes to mind is the New York City Subway. From its roots, it was built as a fully grade separated electric network, with the first underground line opening in 1904. The electric railways that preceded it were mostly grade separated, and any grade crossings that did exist on lines later integrated into the network were removed - the most notable being at East 105 St on the Canarsie Line (today's L train), which was removed in 1973.

Systems in the former USSR are also undisputedly rapid transit. Grade separation is omnipresent, and lines typically run deep underground at incredibly high frequencies. The Moscow and St. Petersburg metros are the two most well known, though modern evolutions still occur.

Finally, many systems in China, India, and the Middle East are being built with the global standards for rapid transit in mind. Many of these lines - including suburban ones - are being built as rapid transit.

Now let's blur the lines slightly, starting with lines that are definitely? rapid transit. Most US metro systems built in the late 1960s-early 1980s such as the Washington DC Metro and Bay Area Rapid Transit focused on the suburbs, with the systems being closer to S-Trains than prior systems in the United States. On this website, we still consider these Rapid Transit, as they were built with the intention of being Rapid Transit systems - to the extent that BART uses a different track gauge than the rest of the US and is entirely incompatible with the national rail network.

Extending along this train of thought (excuse the pun), we arrive at S-Train trunk lines/Passante. For the most part, plugging a tunnel underneath your city to link suburban lines does not turn the suburban lines into Rapid Transit ones. However, the tunnel itself may act as a Rapid Transit line. There are two side effects of the S-Train/Rapid Transit comparison. The first is that some systems such as Merseyrail in Liverpool, the Berlin S-Bahn, and the Copenhagen S-Tog are entirely separate from the national rail networks (primarily due to using different electrification). In the latter two, the lines form a de facto rapid transit network. If it were not for the distances they cover, the lower frequencies on the outskirts, and the fact they brand themselves as S-Trains, we would consider them rapid transit on this website. In the former case, lower frequencies and potential through running along mainline tracks make us consider them firmly on the S-Train category.

How about the other side effect? In this case, it's a tunnel built to rapid transit specifications with suburban lines plugged into the ends. In some cases, the suburban parts were upgraded to rapid transit standards, with all grade crossings removed. This is the case of Metro Bilbao Lines 1 and 2 and Cairo Metro Line 1, where the lines are long and stretch into the suburbs but are clearly rapid transit. In some cases, the suburban lines are still branded as suburban lines. In the case of the Crossrail Elizabeth Line, Paris RER A, the Valencia Metro, and Seoul Metro Lines 1 and 4, the core is obviously a rapid transit line but they through run onto mainline track with lower frequencies in the suburbs. In the case of the Crossrail Elizabeth Line, the line extends beyond the metropolitan fare zones and does not even support the same payment method. In the case of the Valencia Metro, they have grade crossings and even request stops. These are therefore considered S-Trains on this website. In other cases, the suburban lines really are suburban, and they brand the core as a rapid transit line, such as Naples Line 2 and nearly every rapid transit line in Japan outside of the linear motor lines and the ones built prior to the advent of through-service. In the former case, we consider the lines to be S-Trains. In the latter, we consider the lines to be Rapid Transit. Even the Kamiida Line in Nagoya, despite the fact that it is a one station extension of a suburban railway line into the city. Again, the distinction is subjective.

Let's move on to a different topic. Grade crossings and hybrid light rail-rapid transit operation. There are a few good examples of where the rapid transit definition falls apart with regards to grade crossings - Chicago's El being one of them. Many lines have grade crossings in the outskirts, but calling the entire network Light Rail as a result would be inappropriate, so we maintain the rapid transit designation. Even for the Skokie Swift, because there's nothing physically stopping it from traveling down to the loop. Next we have hybrid light rail-rapid transit operation. Cleveland, Oslo, and Rotterdam are the best examples I can come up with. In Cleveland's case, light rail and rapid transit share tracks. Here they do brand the two separately enough, so it's easy to classify them separately. In Oslo and Rotterdam, it's harder. Oslo Line 1 operates as light rail outside of the city center, complete with grade crossings and at-grade operation. The same is true of Rotterdam Metro Lines A and B, which run as light rail to the east and with grade crossings to the west. Line E also operates with light rail and has grade crossings. In this case, we consider Lines A and B light rail and Line E rapid transit. Again, it's subjective, and the boundary between light rail and rapid transit is incredibly blurred.

On a related note, the Tyne and Wear metro runs on mainline track. This an interesting case, but we consider it to remain light metro on this website since the network as a whole does not operate as an S-Train.

We'll close this section with a transition over to the next blog post - Light Metros. In recent years, some rapid transit lines have abandoned high floor heavy rail vehicles for tramway vehicles. All of these lines retain the potential to be converted to light rail networks (and in the case of the LA Metro Green Line, that conversion is under way). Yet this is an interesting area that warrants future observation - the Sevilla Metro and the Ottawa Confederation Line are currently unique but may not be unique for very long.

With that, I close this post. Rapid Transit is an interesting topic that has evolved over the past century and a half, and as the gold standard, systems will continue to aim for it or incorporate elements of it into their design.

Light Metro/Medium Capacity Rail Transit and People Movers are next.