Manchester drivers have been warned that simply checking the time on their mobile phone while behind the wheel could land them with six points and a £200 fine.
Laws about the use of handheld devices have been strengthened in recent years, on the back of research that demonstrated how distracting they can be.
Taking calls, sending WhatsApp messages and posting on social media are all major no-nos in the eyes of the law.
There are even strict rules about employing your smartphone as a sat-nav – it must be in a fixed position and journeys planned in full before embarking.
But one little-known aspect of having your phone in your car is that simply “illuminating the screen” is viewed in exactly the same way.
And with many people using their mobile devices to tell the time, rather than wearing a watch, this could be something that catches out millions of Brits.
Mark Tongue, joint CEO of leading vehicle leasing firm Select Van Leasing, said: “You would have to have been living under a rock not to know how seriously the authorities take the offence of driving while using a mobile phone or smart device.
“There have been numerous campaigns to spread awareness and it does seem that the message is getting through to most people.
“But there are always some who insist they are above the law and continue to use their phones in extremely dangerous circumstances.
“However, there are also plenty of people who don’t realise that even a quick press on the screen to check the time can land them in trouble.
“That’s because it is likely to distract them, even for a split second, from concentrating on the road.”
Section 110 of the Road Vehicles (Construction and Use) Regulations 1986 states: “No person shall drive a motor vehicle on a road if he is using a hand-held mobile telephone.”
It goes on to outline what defines usage, which includes “illuminating the screen” and “checking the time”.
According to Department for Transport figures, there were 15,300 prosecutions for “using or causing others to use a handheld mobile phone whilst driving” last year.
In terms of incidents, 22 people were killed and 652 injured in collisions in Great Britain “where the driver was assigned the contributory factor of using a mobile phone”.
Most people will be looking at a £200 fine and six points on their licence if they are caught. But this can extend to a driving ban and £1,000 fine in more serious cases.
Select Van Leasing’s Mr Tongue said: “The message here is to consider your smartphone completely off limits while you are driving.
“If you do want to use it as a sat-nav, buy a decent holder – which are fairly cheap online – and programme in any routes before you set off, including scheduled stops.
“While it is not against the law to answer a call using a bluetooth speaker system that most modern cars have, it’s worth remembering that this can also be a distraction.
“So think whether it is vital to do so and maybe just wait until you reach your destination before calling someone back.”
