Q: How would you determine how many trips are taken on the london Underground each year?

Clarifying Questions:

1. I’m not quite familiar with London Underground, is it like a subway transit system?
Yes

2. The travel from the first stop to the last stop is considered to be a trip right?
Yes

Assumptions:

London Underground Working hrs per day – 12hrs
No of Routes – 4
The time gap between two consecutive train arrivals at a station – 15min
Time Taken for a complete trip – 1hr
Operates 365 days

So, To calculate the number of trips in a year, lets first first calculate the number of trips per day.

Trips per day:

4 Trains cross the station in an hr = 4 complete trips in an hr. (Assuming that all trains start from different points at the same time)

There will be opposite-track trains as well,
So The Trips per hr (tph) = 8

Considering all the 4 routes = 4*(tph)

Trips per day = 4* Trips per hour * WORKING hrs = 32*12

Trips per year = 384 * 365 = 140,160 trips.