Everyone has heard of Tokyo, Japan's gargantuan metropolitan capital. Tokyo is world famous for its businesses, fashion, cuisine and culture. It is a popular tourist destination for cultural sightseeing and shopping. According to Wikipedia Tokyo ranked third in the Global Economic Power Index and fourth in the Global Cities Index. In 2014, Tokyo was ranked first in the 'Best overall experience' category of TripAdvisor's World City Survey (the city also ranked first in the following categories: 'Helpfulness of locals', 'Nightlife', 'Shopping', 'Local public transportation' and 'Cleanliness of streets'. All of these qualities make Tokyo a fabulous place to live in and to visit. Yet there is another thing that Tokyo is famous for: its extreme rush hour traffic.

After having lived in the greater Tokyo area for over a year I have become familiar with the sea of people moving about during rush hour. There is plenty of information to be had online about Tokyo's insane rush hour traffic on its many train lines. In general, the morning traffic is more intense than the evening because of its shorter duration. The evening traffic lasts until after 10 PM with a peak near 6 PM, but is not as crowded.

Even though many of us are familiar with the sheer volume of people we share the trains with, how many people are actually on the train? What are the numbers involved, and can these be put into perspective? After getting frustrated of being unable to find a seat for the umptieth time on a crowded train home after 10 PM, I decided enough is enough. I wanted to know the facts, so that I knew what I was facing. Knowing the facts helps me cope with a situation better, and also on how to potentially work around it.

So, here are the numbers. Let's put things into perspective.

According to Train-Media, the daily number of train passengers in the Greater Tokyo Area is approximately 20 million. This is more than the individual populations of over 100 countries in the world. Annual train ridership is a staggering 13 billion people, or twice the population of the entire world! By comparison, Germany's trains only transport 10 million passengers per year, or less than 1% of the trains in Tokyo, yet its population is only a little more than twice that of the Greater Tokyo Area.

The trains operating in Tokyo are involved in a mass migration movement. It is therefore no wonder they are often crowded. But just how crowded exactly? I'll take an example from a line that I ride nearly every day, the Denen Toshi line from Tokyu railway. It runs between Shibuya in Tokyo and Chuo Rinkan stations in Yokohama. According to Train Media, daily ridership on this line is approximately 1.2 million passengers. Thus, the average number of passengers transported per hour is about 64,000 since the trains only operate between 5 AM and midnight. According to the Ministry of Land, Infrastructure, Transport and Tourism the hourly number of passengers increases to nearly 80,000 during morning rush hour, but I am certain it is even higher than that. The congestion factor on this line during morning rush hour is 191%, implying the train cars carry twice as many passengers as they are built to accommodate. This pamphlet from the ministry defines 100% occupancy as people being able to sit down on a seat, or hold on to a strap or a pole. At 150％ people can still read an unfolded newspaper, but by 180％ one may only be able to read a folded newspaper. At 200％ bodies touch each other there is some pressure. The highest reported value is 250%, which means that whenever the train shakes, not only the body has to incline and cannot move, but one cannot hold on to a strap or post either. People are literally sandwiched between each other, just like sardines in a tin.

Now we have all the information that we need to build a picture of Tokyo's morning rush hour traffic. With an hourly ridership of 80,000 passengers, each train having 10 cars with an area of approximately 56 m2, and there being about 25 trains per hour, the number of people packed into one square metre is about 6, and assuming a random positioning of people all standing in the train, the average distance between people is just 40 cm. Given that the typical shoulder width of adult males is 40 cm and their typical depth is 24 cm, there is indeed not much more room left to pack additional individuals: the total number of people that can be 'stacked' into square metre is about 9, but in practise it is very difficult to get past 7. The value of 6 is comparable to some rough counts of people within my arm's length in each direction of me that I have done over the past few months. And just for reference, when the congestion factor is 250%, the average interpersonal distance decreases to 35 cm. This is indeed very close to the maximum practical density, and by itself is a good reason to avoid rush hour as much as possible.

One thing I have not yet touched on is the damage to the environment of moving all these people on a daily basis, so a quick estimate is in order. A 10 car train on the Tokyu Denen Toshi line has five motors of 190 kW each, for a total of nearly 1 MW of power and I overestimate that these run continuously at full capacity. I also assume each train has 3200 passengers. Given there are 20 million commuters in the morning implies there are about 6000 trains each using 1 MW of power. Each MWh of electricity burning natural gas (thanks, TEPCO!) emits roughly 520 kg of carbon dioxide allowing grid loss. Therefore each train, assuming it runs at full capacity for two hours, will be responsible for a tonne of carbon dioxide emissions through electricity usage (or about 6000 tonnes per day). Assuming the average commute time per passenger is one hour, and that each passenger commutes 250 times per year implies each passenger will emit roughly 50 kg of carbon dioxide per year for the morning rush hour, or approximately 100 kg per day. This is
about 1% of the average carbon footprint of the Japanese population (about 9 metric tonnes per capita).

The last topic that I want to mention is the sheer volume of money that is being spent each day moving so many people. Recent figures are hard to come by, but Tokyo Metro - the largest underground operator in Tokyo ward - made a profit of JPY 63 billion on a daily ridership of about 6.33 million people in FY 2009. That is a *profit* of nearly 10 000 yen per person, or about 20 yen per ride assuming each person works 250 days a year. If each person on average pays 300 yen for a one-way trip to work this amounts to nearly 7% profit for Tokyo Metro, while Toei - the second underground operator in Tokyo ward - made a profit of about 5000 yen per person (margin of about 3%). The real kicker is the sheer amount of money transportation takes out of the economy: a staggering 3 trillion yen per year!

In summary, Tokyo's rush hour moves the populations of whole countries within the confines of the city boundaries every morning and evening. It is a mass migration movement where the density of people on the trains is close to the practical maximum to the point any train ride becomes uncomfortable. It is amazing that the system works as well as it does, but it has to because any delay will grind the system to a halt, with incoming passengers stranded and overflowing the train stations. The only way to alleviate the congestion is more businesses relocating farther from the city centre or rental prices in the centre decreasing sharply, and more high-rise units being built.

Perhaps some change may be on the horizon. A recent survey found that 40% of city residents in the three major urban areas (Osaka, Tokyo, Nagoya) would like to be able to split their time between city and rural life. The biggest obstacles Money, availability of transportation and medical care. Let's hope that the government is taking the overcrowding seriously. If ELSI were to allow me to work from a rural country home, I'd be the first to sign up!

10pm on a weekday on the Denen Toshi line

Sources:
http://www.train-media.net (Japanese)
http://www.mlit.go.jp/tetudo/pamphlet/n_p03.html and translation http://smt.blogs.com/mari_diary/2005/01/_a_study_says_c.html (Japanese)
http://www.fas.harvard.edu/~loebinfo/loebinfo/Proportions/humanfigure.html (English)
https://en.wikipedia.org/wiki/Tokyu_6000_series (English)
http://search.japantimes.co.jp/news/2010/08/03/news/ubiquitous-tokyo-subways-moving-the-daily-masses/ (English)
http://www.japantimes.co.jp/news/2015/10/18/national/nearly-40-city-residents-also-want-rural-homes-lack-time-money-survey/ (English))
3 trillion: 250 days times 300 yen per one-way ride times 2 times 20 million =