In Dallas TX our lightrail runs about every 15 min too. It's works pretty well and is big enough to be actually useful. I like to use for big events when you know parking is going to be a nightmare or expensive. It's slower than a car though, the trip about doubles in terms of time taking the train vs driving.

Maybe the capitals and major metro ones. My tier-2 EU city is has commuter trains every hour and every 30 minutes at rush hour.

Yeah it sucks, making car commutes the way better alternative.

On a lot of London Underground lines, 5 minutes is considered poor service in rush hour. Every 2 minutes is required to handle the sheer volume of passengers