On the spot fines are deeply annoying. Especially for traffic offences. Especially if you don’t have any form of payment available.
Today’s invention is a pump/flowmeter unit carried by traffic police. This could be used, with the driver’s grudging agreement, to safely and rapidly extract a fine in the form of fuel from a vehicle which had been pulled over for some offence.
This would be taken back to the station, checked that it didn’t contain any illicit or explosive additives and used to power cop cars.
Given the price of fuel, this approach could accommodate some pretty serious roadgoing transgressions.