Coding classes in Tyne and Wear

The learner downloads NaPTAN, the Department for Transport's national register of public transport stops, for the national rail and tram area. Metro station codes start with 9400ZZTW, so filtering on that prefix should give the Metro. It gives 68 stations, and eight of them are named "Edinburgh Trams": Newhaven, Ocean Terminal, Port of Leith, The Shore, Foot of the Walk, Balfour Street, McDonald Road and Picardy Place. Their latitudes sit near 55.97 degrees, far north of Tyne and Wear's 54.90 to 55.04, and they were added on the same day in 2022, while the other Edinburgh tram stops use a different prefix. Checking names and coordinates, not only codes, leaves the true 60.

Now the puzzle. If each trip goes to one of 60 stations at random, the first trip is always new. After that, the chance of a new station falls as the collection grows: with 59 already seen, only 1 station in 60 is new, so that last one takes 60 trips on average. Adding up the waits for each new station gives 60 × (1 + 1/2 + 1/3 + … + 1/60), about 280.8 trips. The sum in brackets is called a harmonic number, and it grows only slowly, which is why doubling the number of stations roughly doubles the trips and adds a little more.

The table holds two lessons. First, the work is lopsided: the first half of the set takes about 41 trips and the second half about 240, because the last few stations are so hard to hit. Second, unequal chances make things much worse. In a made-up version where some stations are ten times as likely as others, the average climbs to about 672, because everything waits on the quietest station, reached on only 1 trip in 330. Real collections, from sticker albums to testing every screen in an app, behave the same way.

So a young person in Tyne and Wear should learn to code in 2026 to check the data before trusting the answer. The longer argument is in why teenagers should still learn to code in 2026.