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A train on the London Underground today (Oli Scarff / Getty Images)

Tunnel Travel

The world’s first subway system turns 150 years old

By Linda Buchwald | May 2, 2011

The world’s first subway— London’s Metropolitan Line—opened 150 years ago, on January 10, 1863. On its first day of operation, 30,000 passengers rode the train along a track that was only 6 kilometers (4 miles) long.

Today, about 3,000,000 passengers ride the London Underground each day, and there are 275 stations along 408 kilometers (253.5 miles) of railway.

Another of the world’s oldest and biggest subway systems is in New York and opened in 1904. It has about 660 miles of track, with more on the way.

New York City has talked about adding a new line on Second Avenue since the 1920s. Now construction is finally under way. The first phase of the massive project that started in 2007 is scheduled for completion in 2016. The new line is expected to reduce crowds and also shorten travel times by 10 minutes or more.

How are trains coordinated so that everything runs smoothly? Subway tunnels have signals that operate like traffic lights. As a train moves along, it triggers circuits on the track that relay information to the lights. The lights behind the train turn red, telling train operators behind it to stop, explains Chris Weida of the Metropolitan Transportation Authority (MTA) in New York City. “You want to have a situation where you have adequate spacing given the expected speeds of the trains on the tracks,” he says.

The time between subway trains in New York City can range from 90 seconds to 20 minutes depending on the line and track design (trains travel more slowly on curved tracks). The time intervals also depend on the time of day. During rush hour, trains come more frequently.

SKILLS SHEET

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This article originally appeared in the January 14, 2013 issue of Math. For more from Math, click here.

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