Coding classes in Kent

The Department for Transport's Port Freight Statistics count every unit through each major port, quarter by quarter, by direction. At Dover a unit is mostly a lorry, trailer or car, since the department notes that its unit totals include non-freight vehicles such as passenger cars. The first job is conversion. A quarter is not a rate. To get vehicles per hour you divide by the hours in the quarter, and a learner who forgets that July to September has 92 days while January to March has 90 gets a small error and learns a large habit.

Now the law. Little's law says that in any steady system, the average number of things waiting equals the rate at which they arrive multiplied by the average time each one spends waiting: L = λW. It needs no assumptions about how arrivals are spread, which is what makes it so useful. At the summer 2025 average of about 300 an hour, an extra check adding 90 seconds to every outbound vehicle adds about 7.5 vehicles to the average queue. Five extra minutes adds 25. Fifteen adds 75. In January's quieter flow, the same 90 seconds adds 4.5.

And here is the honest part. 300 an hour is the average across 2,208 hours, including every night and every quiet Tuesday. Nobody queues at the average. Real traffic arrives in waves: weekend mornings in August, the hours after a ferry is cancelled, the start of school holidays. The quarterly table cannot show those peaks, so Little's law applied to it can only tell you about the typical hour, not the worst one. A learner who writes that limitation next to their answer has learned more than one who just prints 7.5.

So a Kent teenager should learn to code in 2026 not to out-calculate a model, but to be the one who reads the model's answer and asks what it left out. The longer argument is in why teenagers should still learn to code in 2026.