Fun Facts: Subways and Metros Edition

Image: The People's Square Station in Shanghai class=

One of the most interesting things I learned about subway systems while researching for this post is that no one agrees on how long subway systems are. The world’s longest subway system is given by different sources as that of Seoul, Shanghai, Beijing, or London.

Part of the discrepancy can obviously be accounted for by time: the longest subway system in 2002 won’t necessarily hold that record in 2014. But when the site updated in 2003 that claims London is the longest gives its length as 415km, whereas the official Transport for London site currently says 402km—what gives? In this case, I’m tempted just to shrug and chalk it up to human error. But the Seoul subway system is sometimes cited as having a total length of over 900km, making it easily the longest subway system in the world, when other sources give the length of the complete system (it’s run by several different companies, which only adds to the confusion) as between 450-650km. It could be because some are measuring total track length, whereas others are using total route length. The second method makes more sense, since having two lines of track next to each other on the same route doesn’t allow you to travel any farther! Given that distinction, my bet’s on Beijing or Shanghai for the true record-holder—depending on who’s expanded more recently at this point.
Image: Diagrams of the Tünel in Istanbul

The shortest subway is less disputed: the Tünel in Istanbul, Turkey runs on a route of (probably) only 573m (1,880ft). The length is variously given as 554.8m, 573m, and 606.5m; since the English version of the official website doesn’t have the information at all, I chose the one that was both the median and mode as far as the sources I checked were concerned.

Image: Map of the London Underground

The oldest and perhaps most well-known metro system in the world is the London Underground, which first opened as an underground railway in 1863. Operation began on the first electric underground railway in 1890. Despite its name, less than half of the Underground is actually subterranean.

So what makes a subway a subway? If 55% of the iconic Tube is aboveground, where’s the cutoff point? Well, first off, in most of the UK, the word subway doesn’t refer to a rapid transit system but rather a pedestrian underpass below a road or other obstacle. So hardly anyone calls the London Underground by that term. That aside, there is, unsurprisingly, no universal definition for what constitutes a subway. It’s generally lumped in with other names for rapid transit systems, like metro, U-Bahn, and (by some definitions) heavy rail. What any given system is called changes more by locality than by specs.

They are, however, all distinguished from a light rail, which shares right-of-way with street traffic rather than running on its own separate system.


Anupam Mishra on Water Harvesting

Anupam Mishra is an author, environmentalist and water conservationist. In this video from TED India 2009, he talks about the centuries-old water collection and storage techniques used in India’s Golden Desert, the lowest-rainfall area in the country.

When I first watched this video I was in the process of deciding whether I wanted to pursue civil engineering or mechanical. This was one of the influences that tipped me towards the former. At one point, Anupam Mishra talks about a government project to bring water to the Golden Desert from the Himalayas thousands of miles away, and mentions that many of those canals are now covered in lotuses or sand. The systems that were locally designed and built, on the other hand, are still in use hundreds of years later.

I like the idea that a core part of my career could be asking not just, “Will this work?” but, “Will this work here, in the long term?”

I like the idea of being involved in something that could, with some maintenance, be used hundreds of years later.

And I really like locally effective solutions that capitalize on their surroundings rather than just trying to impose the same thing everywhere.

Infrastructure: Not Just for Humans Anymore?

Toads making their way through a concrete-walled tunnel

A toad tunnel in Wales

Toad tunnels might seem like kind of a wacky idea at first glance. That’s especially true if you’re looking at the one that’s referenced most often: it’s located in Davis, California, and has a cutesy little wooden house topped with solar panels near the entrance.

Toad Hollow: a pair of small green houses no more than three feet tall grace the entry to the Davis, CA toad tunnel.

Toad Hollow

Tunnels built to let amphibians cross highways without getting hit by passing cars have been used in Europe for decades, according to a National Geographic article on the subject. During breeding season, usually March or April, hundreds of frogs, toads, and salamanders may have cross roads to get to their habitual spawning grounds.

There are definitely reasons to be skeptical about amphibian tunnels. If they’re not built right, the critters are likely to skip the entrance altogether. Scott Jackson, a biologist quoted in the article mentioned before, says tunnels should be about two feet by two feet and “fitted with an iron grate [across the top] to allow sufficient air, light, and moisture into the tunnel.” If there’s not enough moisture along a tunnel to keep an amphibian happy, it might just turn around and look for a different route.

A tunnel under a road in the process of being built

The SPLAT project’s tunnel, under construction

The morbidly-named SPLAT project on Vancouver Island, BC has spent the last four years working with the B.C. Ministry of Transportation to design and build an experimental tunnel, after a previous five years of catching amphibians in pit traps and carrying them across. The SPLAT blog details the methods they’ve tested over the years for creating a comfortable passageway and funneling amphibians into it rather than the more dangerous overland routes. So far, they’ve recorded nearly 300 frogs, newts, and salamanders moving through it, and they’re continuing to improve on their design.

A map of the Appalachian trail, a red line extending from Maine to Georgia.

The Appalachian Trail is one of the largest and best-known conservation corridors in the US.

Amphibian tunnels are a miniature example of a wildlife corridor, or conservation corridor. Conservation corridors are usually long and narrow areas of protected or restored wilderness, which connect what are known as habitat fragments—wildlife habitats that have been blocked off by human activity. The idea is for populations to be able to mingle and breed, as well as to clear paths for north-south migrations.


Engineering has historically been focused on improving life for humans, and taking care of the rest of the world has been a specialized goal for naturalists, biologists, and environmental activists. However, recognition is growing across industries that ignoring environmental concerns is not a great long-term strategy. A Google search for “green engineering” brings up about 402,000 hits, for example. This might, of course, be partly because of how many companies are realizing that “going green” is a wonderful way to market to the growing number of people who are worried about the environment but aren’t quite sure what to do about it—but that’s another blog post.

Bringing environmentalism into engineering, and vice versa, does involve some growing pains. Changing longstanding beliefs and values of any culture is not easy work. On the other hand, engineers often have a great talent for getting enthusiastic about new ideas and ways of doing things. The authors of Cradle to Cradle tell a story about an engineer working on the ecologically-conscious redesign of Ford’s River Rouge plant who went from refusing to “[talk] to no eco-architects about no eco-architecture” to being one of the project’s most dedicated supporters. I, for one, look forward to watching what comes from this unlikely-but-necessary marriage.