Every year, a truck runs away down a hill on burned-out brakes - and the report always says the same thing: the service brake was asked to do alone what the gearbox and the retarder were there to share. Brake fade is not bad luck; it is a technique failure with a long warning trail, and the Highway Code’s rule against coasting exists precisely because of it.
The service brake converts motion into heat, and heat is the enemy: drums and discs that get hot enough stop biting, the friction material glazes or the fluid boils, and the pedal that worked at the top of the hill goes soft halfway down. The cruel arithmetic for a truck is mass: energy rises with weight and with the square of speed, so a laden artic descending a long gradient at the speed limit is generating heat at a rate the foundation brakes were never meant to sustain continuously. They are a stopping brake, not a speed-holding brake - the hill that treats them as one will collect the difference.
The Code’s coasting rule spells out the physics in plain terms: coasting - in neutral or with the clutch held down - eliminates engine braking, so vehicle speed downhill increases quickly; increased use of the footbrake then reduces its effectiveness; steering response suffers, particularly on bends; and it becomes harder to select the right gear when it is suddenly needed. Every line of that is a brake-fade paragraph. The rule’s instruction to select the appropriate gear before the descent is the whole technique in one sentence: the gear chosen at the top is the brake you keep at the bottom.
The professional descent is decided before the hill starts. Read the signs: the gradient boards and the escape lanes are the hill announcing its terms. Select the gear at the top: the gear that will hold the load’s speed with engine braking alone, or close to it - for most laden trucks that is two or three gears below the cruise. Use the retarder as the primary speed holder: the exhaust brake, the engine brake or the driveline retarder is the wear-free brake that does not fade - on trucks so equipped it should be doing most of the work, and drivers should know its controls before the mountain, not on it. Then the service brake is the trimmer: short, firm applications to knock speed back when it builds, never a long dragging press that pumps heat in faster than the brakes can shed it. And the honesty rule: if the brakes start to smell, soften or fade, the decision is immediate - a lower gear, a stop in a safe place to let them cool, and no pride. The escape lane exists for the day the honesty comes late.
Technique saves brakes; maintenance saves them too. The faded brake on the hill was often the neglected brake in the yard: the imbalanced axle that roller-brake testing flagged, the contaminated linings, the air system with the slow build time. The fleets that never meet fade treat the brake test numbers as hill insurance - the imbalance found at the PMI is the fade that never happens on the road.
Fade is heat, and heat is technique: gear down at the top, let the engine and retarder hold the speed, trim with the footbrake, and never coast - the Highway Code’s coasting rule is the fade-prevention rule written in general terms. Keep the foundation brakes as the reserve, and they will be there when they are the only thing left.
The descent technique is a training topic, not a handbook chapter: the driver who learned it from a pamphlet meets his first real alpine-style gradient alone, at night, with 40 tonnes behind him. The fleets that take it seriously build it into the driver programme - the assessed drive over the fleet’s hardest route, the demonstration of what dragging brakes feel and smell like at the point of no return, and the route notes that flag the descents demanding respect: the long Welsh drops, the Pennine crossings, the Scottish passes on the trunk network. Retarder familiarity belongs in the same programme: the control differs by manufacturer, and the driver hunting for it at the top of the hill has already lost the argument. The hill is a patient teacher, but its fees are the worst in the industry.
One gear lower than feels necessary, the retarder doing the holding, the footbrake in short firm trims, and no coasting ever - the descent survived on technique is uneventful by design. The fleets that never feature in the runaway reports are simply the ones whose drivers were taught to be boring on hills.
One more truth about descent technique: it changes with the load. The empty truck can hold itself on engine braking in a gear the loaded truck burns through; the driver who runs the same hill both ways learns to choose the gear for the weight he has, not the weight he had yesterday. That is also why the laden test routes of the old driving-school hills taught the lesson properly - a technique that only works empty is not a technique. Fleet trainers worth the name brief the gradient, the gear and the weight as one sentence, because the hill reads all three at once. And the driver who is unsure errs downward: the gear that feels too low at the top is very often the gear that was exactly right by the bottom.