Many claims these days suggest that automotive brake failure directly contributed to an accident. For those losses where brake malfunction is a suspected cause, the claims investigator is obliged to look into the existence of evidence of brake failure.

Figure 1 to the right offers a brief review of an automobile brake system. The brake pedal presses against a vacuum assist brake booster that pushes on a master hydraulic cylinder, resulting in increased hydraulic pressure in brake lines. The brake lines are connected to brake calipers or brake shoe wheel cylinders, causing increased friction on the brake drum or rotor, resulting in vehicle braking.

Older vehicle master cylinders supply hydraulic pressure to all brakes via one brake line (arrow Figure 2). Unfortunately, if a leak occurs in a brake line, then the whole system loses pressure, and fails. Modern brakes have dual master cylinders that operate two independent systems, which have proven more reliable. Modern brake systems are also equipped with anti-lock features that have improved performance on certain road surfaces.