The National Highway Traffic Safety Administration (NHTSA) estimates that without TPMS, there are 23,000 traffic accidents involving a flat or puncture tire each year, with 535 fatalities. Both of these problems may be caused by improper tire pressure. For safety reasons, the U.S. government enacted the Transportation Equipment Recall, Improvement, Liability Determination, and Documentation Act (TREAD). As part of the TREAD Act, the Federal Motor Vehicle Safety Standard (FMVSS 138) requires that all cars, trucks and buses manufactured in the gross weight class up to 10,000 pounds or in small batches must have a TPMS installed since 2008.

　　The rest of the world is also recognizing the safety issues associated with abnormal tire pressure. In France, Sécurité Routière estimates that 9% of traffic fatalities are caused by underinflated tires. Germany's DEKRA estimates that tire-related problems account for about 41 percent of all traffic fatalities, noting that without TPMS, 75 percent of vehicles on the road have at least one tire that is 3 psi (20 kPa) or more deficient.

　　In addition to improving safety, properly inflated tires can also improve vehicle fuel economy. As a result, many regions have or will require the installation of a TPMS.

　　Getting the tire pressure right isn't just about getting the tire pressure to the manufacturer's recommended range. Some situations may also cause problems for the driver.

　　First, the air pressure recommended by the manufacturer is a "cold" air pressure. The tire pressure is measured after the vehicle has been stopped for more than an hour. The measured tire pressure is determined by the tire's load-bearing capacity, and the tire pressure will rise while driving. Tire pressure measurements should not be adjusted down to estimate cold tire pressures when tires are hot from driving, even though most tires typically increase tire pressure by about 3-5psi (20kPa-35kPa) per square inch while driving tire pressure monitoring system.

　　A tire pressure gauge typically measures the difference between the external ambient pressure and the tire's internal pressure (called gauge pressure). However, tire pressure is affected by changes in altitude. For example, a car with properly inflated cold tires at a high altitude (eg, Flagstaff, Arizona) will be underinflated, about 3 psi (20 kPa) less, when driven to a lower altitude (eg, Phoenix, Arizona). Likewise, driving to Flagstaff with properly-inflated tires in cold Phoenix will be over-inflated, about 3 psi (20 kPa) higher.

　　Seasonal temperature changes are also factors that affect the appropriate tire pressure. Even ignoring the loss of air pressure from tires that have not been in use for a long time, setting a cold air pressure in summer (say, about 32°C at 90°F) will be better than setting it on a winter morning when the temperature is 0°F (about -18°C). A reduction of about 16%.

　　Without TPMS, drivers who do not check their tires are often, or in some cases, likely to use tires that are not properly inflated and are therefore at risk of driving.

　　A direct tire pressure monitoring system is an early warning system that warns the driver of a vehicle when there is an unsafe change in the pressure of one or more tires. A pressure-sensing transmitter is installed inside each tire, and the readings are sent directly to the central control unit (ECU), which is then displayed on the instrument cluster. If the pressure drops by more than 25%, a warning light on the instrument cluster will illuminate and an audible alarm will sound to alert the driver.

　　For both direct and indirect tire pressure monitoring systems, a warning light on the instrument cluster illuminates whenever a 25% or more drop in tire pressure is detected. Direct tire pressure monitoring system alarm faster, if the car has a four-tire tire pressure monitoring system display function, it can also display the specific readings of each tire. One of the biggest drawbacks of indirect tire pressure monitoring systems is that they cannot detect when all four tires are low pressure, which can happen frequently if tire pressures are not checked regularly.