New mobile phone laws which came into force last month mean anyone who touches their phone while the engine is running is breaking the law.
Therefore you could be breaking the law for using a smartphone to pay at a drive-through fast-food restaurant.
Cleveland Police has advised people that they should switch off their engine when using contactless payment - or face a fine of up to £200.
As well as the fine, drivers can have six penalty points imposed on their licence if they use their phone while driving.
A Cleveland Police spokeswoman said: ‘We have got to take a common sense approach, but ultimately the law states you shouldn’t use your phone with your engine running.’ The force says it makes no difference if the drive-through is on private land.
Drivers are advised to switch off their engine and put the handbrake on if paying using the phone - or just use a contactless card.