Retarders have traditionally been credited with reducing brake maintenance costs of large trucks and lowering trip times. This paper presents methods for quantifying the resulting productivity increases. A Brake Life Extension Factor is developed and shown to increase as retarder horsepower increases. Four common retarder technologies are discussed (exhaust brakes, engine brakes, electric retarders and hydraulic retarders). A method is shown for computing the return on investment in a retarder, based on only the brake maintenance savings, using a discounted cash flow analysis. The impact on capital of faster trip times is examined.