Device to measure road dustiness on aggregate surfaced roads

Dust emissions from vehicles on unpaved roads can cause serious air pollution, impair visibility and safety for motorists, and pose an overall hazard to health. Appreciable maintenance dollars are spent each year for the control of dust on unpaved roads. Renewed interest in evaluating current dust control management has been stirred from the high maintenance costs, increased road user costs, loss of surface fines, and public awareness of pollution problems. Currently, decisions regarding the type, quantity, and time of application of a dust control method are based upon "human judgment", an informal, qualitative process. Studies on ways to reduce dust control costs are focusing on more efficient and uniform use of dust control methods. This requires a quantitative system to measure the level of road dustiness. With over 2.2 million miles of aggregate and earth-surfaced roads in the continental United States alone, there exists a significant road dust problem. The Cornell University Local Roads Program is developing a Road Dust Monitor capable of quantitatively measuring levels of road dustiness as part of a study sponsored by the USDA Forest Service. It is anticipated that this instrumentation will provide a repeatable and reliable method of measurement and form the basis for dust control management. The present prototype Road Dust Monitor consists of an eight-inch by twelve-inch duct in an L-shape, a transducer mounted on the duct, and an instrument package with an indicating meter. The duct and transducer are positioned behind the left-rear tire of a pick-up truck and the instrument package is mounted near the driver in the vehicle cab. Equipped with a light sending and receiving unit, the transducer shines an infrared light beam onto a reflector and this reflected light is detected by the receiver. As the moving vehicle kicks up dust from the road surface, dust passes through the duct, partially blocking the light beam and reducing the light reflected back to the receiver. The air opacity is converted to an analog voltage which is displayed on the indicating meter.