Drivers are being reminded to switch off their engines at level crossings to help the environment.
East Anglia has over 800 level crossings and according to Greater Anglia just one stationary car could fill up to 150 balloons per minute with exhaust fumes.
The train operator has joined forces with other organisations on Clean Air Day to encourage people to switch off until the barriers are up.
The Royal College of Physicians say tens of thousands of deaths a year in the UK are linked to air pollution.
Engines that are idled can be more polluting than those that are in motion. Sulphur dioxide and nitrogen oxide can all enter the atmosphere.
Posters, car window stickers and social media posts are all being made to try and spread the message.