Brake systems are one of the essential components of vehicles ensuring the safety of roads and passengers as well as accident prevention. Faulty brake systems, however, can cause inevitable accidents. Fatality analysis reporting system of NHTSA (National Highway Transport Safety Association) has reported that heavy and light trucks, which are obliged to be equipped with dual-circuit air brake system, were, respectively, involved in 8.8% and 38.0% of fatal crashes in the United States, during 2017. Number of heavy vehicle accidents due to complete failure of brake system is far less than accidents due to deficiencies such as worn out brake linings, out-of-adjustment push rod strokes, and leak in the circuits. Severe leakages due to ruptured air hoses or punctured reservoir are highly unlikely to be replenished by compressor and would be distinguished through pressure indicator. Yet, reservoir pressure drops due to small leakages are bound to be replenished by compressor, and therefore would not be distinguished. In this research, air brake system is modeled in Simulink, Matlab, and corroborated by literature, then dual-circuit air brake system of truck 1921 from Iran Khodro Diesel products has been simulated in Simulink, Matlab, and leakage has been introduced in different pressure lines and its effect on brake chamber pressure and reservoir pressure has been investigated. In this regard, two common tests of BS ISO 7635, in the presence of leakage have been simulated and the results have been compared so as to determine the level of sensitivity of each pressure line to air leakage. The risk of road accidents due to air leakage can be reduced by proper and periodic inspection of this pressure lines and accidents could be prevented.
