Starting from 1st November 2012 all new car models to be phased in the European Community should have integrated tyre-pressure monitoring systems. This obligation, adopted in the US since 2008, represents important news in terms of car safety. A market survey lead by Goodyear Dunlop shows that at least 73% of the persons interviewed don't know the correct pressure of their tyres in the various drive conditions. Integrated system can be direct or indirect. The first ones, also called TPMS (Tyre Pressure Monitoring System), detect actual tyre pressure thanks to sensors (inside or outside each tyre). These sensors can detect pressure both on parked vehicles and in driving conditions.
The seconds, called indirect TPMS or DDS (Deflation Detection System) detect pressure by checking the rolling speed of each tyre. A flat tyre has indeed a smaller diameter than a properly inflated one. These differences are shown by ABS/ESC wheel speed sensors.