If your tyres are under or over inflated it could lead to low fuel consumption and accidents. In most countries, you could be fined if the pressure is low enough to make the vehicle unsafe for driving. The punishment could be a hefty fine and a deduction of points on your licence.
The safest way to ensure that your tyres are inflated to the recommended level is to invest in a pressure 
gauge and a tyre inflator. While the gauge can regularly be used along with the tyre inflator it has the added advantage of helping to cope with a tyre puncture. The tyre pressure will vary depending on whether the vehicle is loaded or travelling with only the driver.It is a matter of major concern if you are using a pickup truck or any other heavy vehicle.
If the vehicle is under inflated the braking distance would be much longer. Added to this danger is the fact that fuel consumption would be much higher as the vehicle uses up more power to get into motion. If it is overinflated, it could lead to vibration and cause serious damage to the steering and suspension systems.
Most motorists are now aware of the problems caused by incorrect tyre pressures. Those who are not are a menace to other drivers. It is vital to check your tyre pressures before you set out on a long trip or if you are driving in slippery road conditions. In countries that experience snow tyre pressures would need to be more frequently checked. A 
positive indication that your tyre pressures are wrong is when the vehicle swings to a side. This indication could be because your alignment and camber are not properly set but more often it is the tyre pressure particularly if the vehicle is relatively new.
Motor Cyclists need to take even more precaution regarding tyre pressures as the two wheelers need to be properly balanced when negotiating bends.Racing drivers are often seen indulging in pit stops when they have a quick tyre change.It is because the air pressure alters under extreme heat and a new set of tyres become necessary. The tyre pressure on Motorcross thoroughbred bicycles undergoes a
check before a race.