USING smartphones to access social media while driving represents a greater threat to road safety than drugs or alcohol.

Research by the Institute of Advanced Motorists (IAM) found that accessing sites such as Facebook while behind the wheel had a more dramatic impact on reaction times and driving awareness than texting, alcohol and cannabis.

Despite the research – which drew from tests conducted in a driving simulator – far more motorists regard smartphone use while driving as acceptable. The road charity said this was partly because there have not been public awareness campaigns similar to those that targeted drink-driving and, more recently, drug-driving.

The IAM pointed to earlier research showing that 8% of drivers admit to using a phone for emails and social networking while driving, the equivalent of 3.5 million licence holders.

Similar research, conducted last year by the RAC, found that nearly one-quarter of drivers aged between 17 and 24 – a group already considered to be at a higher risk of having a crash – admitted to using smartphones.

The IAM has now urged the Government to take action to highlight the dangers of using a smartphone behind the wheel, and for phone manufacturers and social media providers to help spread the message.

Simon Best, chief executive of the IAM, said there was a need for a public awareness push similar to those about drink-driving and wearing seat-belts.

Mr Best said: "This research shows how incredibly dangerous using smartphones while driving is, yet unbelievably it is a relatively common practice. If you're taking your hand off the wheel to use the phone, reading the phone display and thinking about your messages, you're not concentrating on driving.

"It's antisocial networking; it's more dangerous than drink-driving and it must become just as socially unacceptable."

The research was conducted in collaboration with the Transport Research Laboratory (TRL), using its DigiCar driving simulator.

Participants who were sending and receiving Facebook messages saw their reaction times slowed by 38% and often missed key events. They were also unable to maintain a central lane position or respond quickly to a car in front changing speed.

The impairment was slightly higher than for texting and significantly higher than the effects of cannabis, which led to reaction times being slowed by 21%. Being over the limit for alcohol – but below 100mg per 100ml of blood – slows reaction time by between 6% and 15%. The current drink-driving limit is 80mg per 100ml of blood.

Nick Reed, a senior researcher at TRL, said the tests showed that driver behaviour was "significantly and dramatically impaired" when phones were used for social networking.

He said: "Drivers spent more time looking at their phone than the road when trying to send messages, rendering the driver blind to emerging hazards and the developing traffic situation.

"Even when hazards were detected, the driver's ability to respond was slowed. The combination of observed impairments to driving will cause a substantial increase in the risk of a collision that may affect not only the driver but also their passengers and other road users."

The research comes as the Scottish Government launched a campaign to persuade drivers to take fewer risks on rural roads.

A survey conducted ahead of yesterday's campaign launch found that 70% of drivers admitted to taking risks while driving, including phoning or texting while behind the wheel.

However, the Association of British Drivers, which campaigns against speed restrictions and road safety enforcement, cautioned against being "over-zealous" in banning smartphones, saying many motorists used them as a replacement for stand-alone satnavs.