An insurance company is allowing young motorists to pay less for insurance if they avoid driving at night.
The scheme is aimed at cutting accidents involving young people
More Than is offering drivers between 18 and 25 40% off if they do not drive between 2300 and 0600. But it will charge £25 for breaking the "curfew".
Car use is monitored by a device put into the vehicle by the company.
Up to 40% of accidents between 2300 and 0600 involving young drivers result in death or serious injury, compared with 20% at other times, figures show.
Once installed, the device sends a message to the company whenever the car starts, giving the time and place that the journey started.
A further message is sent when the engine is switched off to confirm the journey has ended.
More Than says the policy could save the average young motorist about £300 a year.
However, BBC News personal finance reporter Richard Scott says drivers who repeatedly break the rules and are charged each time could see their savings wiped out.
More Than also says that by reducing the number of young drivers on the road at night, its initiative could help cut accident rates among young drivers by up to 25%.
Spokesman Bryan Turner said: "High accident rates for young drivers on the roads at night are a major issue and we have been working for some time to come up with a solution to reduce these."
Mary Williams, chief executive of road safety charity Brake, has welcomed the initiative.
She said: "We need to find more innovative ways of preventing tragic deaths involving young drivers and their passengers on our roads."