Friday, January 25, 2008

It pays to be lazy

As a grad student, chances are you're going to work/school by bus. The bus which goes to our hospital is notoriously unreliable. Have you ever been in the situation where you're debating waiting at the bus stop or walking in the right direction hoping the bus won't pass by you? Are you as obsessed as I am to make the most efficient decision? Well some mathematicians have worked it out for us, and the answer is pretty intuitive, you'd better wait in the cold, unless the bus goes by less often than once per hour and the distance to the next stop is under 1km...

"Justine Chen of the California Institute of Technology, and Scott Kominers and Robert Sinnot, both of Harvard University, have drawn up a formula to calculate whether waiting or walking is the best option for those facing a sporadic bus service. Their equation has these variables: n, for the number of bus stops spaced along the bus route; d, for the distance along the bus route; Vb, being the bus speed; Vw, the walking speed; and p(t), being the probability in time that a bus will show up."


2 comments:

kamel said...

Interesting. Depending on where I'm going, I often opt to walk rather than wait, but I think stops are less than 1km apart in those cases.

Bayman said...

That's all good and well, but what about running to the next stop to catch up with the previous bus that you already missed? How many stop lights does the bus have to hit and how fast does one have to run?

I clearly remember in elementary school days just missing a bus in front of my house and then cutting it off to get to the next stop before it did...