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March 02, 2013

Bunching

What made St. Clair streetcars bunch up like this?

You know how the old cliché goes - you wait ages for a bus then two come along at once. Here in Toronto, that saying extends to comical numbers of streetcars too. Case in point yesterday on St. Clair where Reddit user z24lucifer spotted a line of vehicles that appears to stretch to the snowy horizon.

Bunching theory: Why three buses come at once.

Public transport vehicles – underground trains, for example – set off from the start of their routes equally spaced. The problem starts when one is briefly delayed, making more time for passengers to accumulate at stations further down the track. Since passenger boarding is the main factor delaying trains, these extra people slow the train even more.

Meanwhile, the gap between the delayed train and the one behind is shortened. That means fewer passengers for the train behind to pick up, making it pass through stations faster until it catches the train ahead. Eventually, all the trains on a route can end up crawling after the slowest, lead train.

Hat tip to the Sister of the Flea.

Posted by Ghost of a flea at March 2, 2013 08:24 AM