Drivers who break down on almost 1000 miles of Scotland's rural roads cannot call for help because there is no mobile phone coverage, according to a motoring charity.

A study by the RAC Foundation found 4,561 miles of road - representing about two per cent of the entire network - do not have any 2G coverage, which is the minimum required to make a call or send a text.

The Highlands is the worst affected with a total of 452 miles out of range of signals.

It names the A93 a blackspot. It runs across a hilly, then mountainous and treacherous route from Perth through Blairgowrie and Rattray, then through the Grampian Mountains by way of Glenshee. It passes Braemar, near The Queen's Balmoral holiday castle, before crossing the A90 and ending in Aberdeen.

Dumfries and Galloway has 237 miles, including along the Solway Coast, which are also badly affected by lack of signals. A further 226 miles of roads in the Borders were also highlighted as problematic for mobile phone users in the study. In total Scotland has 913 miles of blackspots.

A further 28,975 miles have partial 2G coverage, meaning only certain mobile operators provide a signal.

Motorists who rely on their smartphones to access the internet for route planning and to check for congestion could get into difficulty on 14,554 miles of road, estimated at about six per cent, with a complete absence of 3G coverage, the study found.

An additional 111,679 miles (45per cent) is only covered for 3G by some operators.

In terms of 4G, more than half (56 per cent) of the road network has no coverage, while over a quarter (27 per cent) has only partial coverage.

The research was based on analysis of data published by communications regulator Ofcom.

RAC Foundation director Steve Gooding said: "There are thousands of miles of road along which you would not want to break down or have an accident because calling the RAC, the emergency services or even home wouldn't be an option.

"Even where there is partial network coverage it might not be from your network provider.

"The concepts of connected cars and drivers is at the heart of much thinking about how we might make our travelling lives easier. But the best ideas in the world will fall at the first hurdle if there are no bars on the phone."

Other badly affected routes include the A149 in East Anglia, A591 in Cumbria, and A494 in Wales.