An efficient apparatus for converting momentum into useful work is provided. The apparatus is disposed within a roadway such that when a passing automobile drives over the device, the top of the device is moved downward on a hinge causing a pulley attached to a clutch to rotate a shaft. The clutch ensures that on the “up-stroke” the shaft is not rotated in the opposite direction. Through a series of pulleys, an optimum gear ratio is achieved finally connecting to a generator to output electricity. The top of the device is returned to be even with the roadway by a spring loaded wheel assembly. The apparatus is designed to accommodate loads up to 18,000 lbs and be capable of being deployed across a multi-lane roadway.