Under the rules, each car must be equipped with two independent brake circuits. In other words, if a brake circuit fails, the vehicle can be stopped by using the remaining.

Dual circuit brake system must meet the requirement of an emergency brake that the failure of one brake circuit should still work the second circuit. There are many possible kinds of involvement and duplication brake lines.

a/ standard connection TT – in each circuit is braking one axle
b/ diagonal connection K – in each heading is braking one front and one rear wheel (always diagonally)
c/ connection HT – in one circle is inhibit the front and rear axles, second circuit controls only the front axle

d/ connection LL – each circuit brake front axle and one rear wheel
e/ connection HH – each circuit brake all wheels