Correct tire pressure is vital to your safety on the road. Under-inflated tires affect handling and grip, potentially causing irregular or unpredictable vehicle behavior. They are also much more likely to suffer from a dangerous sudden rapid deflation, especially on high-speed motorway journeys.
By keeping your tires at their optimum pressure, your running costs are also reduced. Under-inflated tires require a bigger force to make them turn, so your car uses more fuel. Additionally, tires which are not set to their correct pressure wear out more quickly.
So, to benefit from lower fuel bills, longer tire life, increased safety, and reduced CO2 emissions, make sure you check your tire pressures at least once a month and before a long journey.