Almost one-third of pedestrians are distracted by mobile phones when crossing busy roads, a new study has found.

Scientists observed over 1,000 pedestrians crossing 20 busy junctions in a US city during the summer of 2012. They looked specifically at ‘distracting' activities, including talking on mobile phones, texting, listening to music and dealing with children.

The study found that while eight in 10 people obeyed the traffic lights when crossing a road, just one in four used the full safe cross code, including looking both ways before crossing.

Furthermore, almost one in three were doing something else while they crossed the road, including talking on the phone and texting.

The scientists noted that those who were distracted by a phone took a lot longer to cross the road. And while those listening to music on a mobile device were faster crossing, they were less likely to look both ways before doing so.

People distracted by children and/or pets meanwhile were much more likely not to look both ways.

However overall, texting was found to be the most distracting activity. Texters took longer to cross the road and they were almost four times more likely to fail to look both ways before crossing, ignore traffic lights and cross at the middle of a junction.

The scientists said that this problem is set to get worse as mobile devices become even more popular. They called for a low tolerance approach to be taken.

"Ultimately a shift in normative attitudes about pedestrian behaviour, similar to efforts around drunk-driving, will be important to limit the risk of mobile device use," the team from the University of Washington said.

Details of these findings are published in the journal, Injury Prevention.