a non level road surface is detected with reference to fig1 the economical system is depicted system 100 includes a selectively variable orifice 118 positioned in a hydraulic fluid line 116 of the vehicle variable orifice 118 has a control input 105 coupled to the orifice between the orifice and an auxiliary brake control unit 104 a power train control module or a specialized electronic control module for the vehicle 108 activates and deactivates auxiliary brake control 104 in accordance with a vehicle speed sensor 102 a clutch pedal sensor 110 a throttle sensor 112 and a brake pedal sensor 114 each of these sensors being coupled to an input of power train control module 108 in production vehicles equipped with cruise control the cruise disconnect switch associated with the clutch in a manual transmission could be used as the clutch pedal sensor it will be apparent to those skilled in the art however that a separate clutch pedal activation sensor 110 could be provided with the system as arranged in fig1 the method for activating a hill hold function is performed by power train control module 108 in accordance with the flow chart set forth in fig3 the routine is entered at 302 and initially a test is performed to determine whether the brake pedal is beginning to release at step 304 this test is maintained as long as the answer is no if the brake pedal is beginning to release then.