New research claims the use of sat nav devices can increase drivers’ risk of crashing.
Motorists were significantly distracted when trying to follow particularly complex audio directions from their sat navs, the study found.
This could lead to them driving less safely, psychologists at Royal Holloway, University of London, and spatial scientists at Lancaster University said.
Preference for audio directions
The study found that drivers who use sat navs were more likely to use audio descriptions of their routes than the visual aid on the device's screen.
Royal Holloway’s Dr Polly Dalton said that the message for sat nav manufacturers was that instructions should be kept as simple as possible.
"People are capable of following spoken instructions in a car and it's actually a really good way of presenting information to them.
"But it's important not to make those directions too complicated because that runs the risk of asking them to keep too much information in mind when they are also trying to concentrate on the driving task.”
'Difference in driving ability'
Dr Dalton added: "What is interesting is that people were able to follow one simple instruction without any significant impact on their driving.
"But as soon as they had to remember a compound instruction, consisting of two sequential directions, we began to notice a difference in their driving ability."
Dr Pragya Agarwal at Lancaster University added: "With the increasing reliance on technology for navigation, it is important that such technology is designed so that it supports rather than detracts us from our primary task of driving.
"We hope that this research will contribute to the development of guidelines for the design of more effective, safe and user-friendly in-car navigation systems."
The researchers stressed, however, that using a sat nav was likely to be safer than trying to look at a map while driving.
The scientists' findings are the latest challenge for companies which make sat navs.
Earlier this year, the government held a summit aimed at ending the problems caused when motorists followed out-of-date directions from their sat navs.
Following the summit, local transport minister Norman Baker said: "Out-of-date directions mean misdirected traffic – a scourge of local communities.
"I am pleased that highway authorities, mapping companies and satnav manufacturers have agreed to work more closely to provide drivers with accurate, up-to-date information on traffic restrictions such as narrow roads or low bridges."