Carefully worded road signs have helped "significantly" cut pollution at busy railway crossings, a study has found.

Psychologists at the University of Kent fixed three signs to lampposts at the St Dunstans and St Stephen's level crossings in Canterbury, encouraging people to switch off their car engines while stationary.

Concerns have previously been raised about air pollution in these spots, where drivers frequently leave engines idling during queues when barriers are down.

The signs contained three different messages, such as: ‘Join other responsible drivers in Canterbury. Turn off your engine when the barriers are down’.

The study found the signs increased the proportion of drivers turning off their engines by up to 42%.

This in turn improved air quality, by "significantly reducing" concentrations of pollutants.

After observing more than 6,000 drivers, researchers found the signs were especially effective when there were large queues at the crossings.

They found people "may feel a stronger urge to conform to the norm of turning their engines off when those ahead of them in traffic do too".

The research, published by the Journal of Environmental Psychology, is the first of its kind to show that behavioural change induced by persuasive messages translates into real changes in air quality and pollutant levels.

The research was funded by Canterbury City Council following a successful bid for a grant from the Department for Environment, Food and Rural Affairs (DEFRA), and was led by Professor Dominic Abrams, Dr Tim Hopthrow and Dr Fanny LaLot, of the University of Kent's School of Psychology.

As a result of their findings, the city council has now installed permanent road signs at the St Dunstans, St Stephen’s and Sturry railway level crossings.

Prof Abrams said: "People have many creative ideas about how to improve air quality, but how do we know which will work?

"This research used a scientific method that enabled us to design effective messages to change people’s behaviour, improving the air quality for themselves and others.

"Just as importantly, we have also discovered types of messages that do not work so well.

"This approach should also work when planning ways to encourage other behaviours that can improve air quality, health and quality of the environment."

Kelly Haynes, environmental health officer for air quality at Canterbury City Council, added: "Improving air quality in the district is a major focus of the council and research like this is vital to that work.

"The results clearly show the right messages in the right locations can be really effective in reducing the number of people leaving their engines running which is one of the main contributors to poor air quality in our city.

"These signs are just one of many things we're doing to tackle air quality including the introduction of a new hybrid car club in Canterbury and plans to install more electric vehicle charging points across the district."

Read more: All the latest news from Canterbury