Your taxi charges by the second when you drop below 20 km/h

Aitor Gorospe, twenty-four years behind the wheel in Bilbao, explains it plainly: 'Every week someone in the back asks whether my meter is rigged. I show them the green sticker on the window.'

Across Spain the device has two speeds: one per metre driven and one per second stood still. The meter picks, at every instant, whichever brings in more money. Above 20 km/h the kilometre rules; below it, time rules. A car stuck on Bravo Murillo at nine in the morning adds, in Madrid, around €0.66 a minute under Tariff 1: five euros for ten minutes of not moving.

This is required by Order ITC/3701/2006 on legal metrology, which forces the sealed meter to display the waiting fee per hour. It sits under the meter, in tiny print on the green sticker: 'waiting time: XX.XX €/hour'.

Next time the number jumps while the car is still, look at that pane. It tells you what time you're paying for.