Speed measurement through analysis of the Doppler effect in vehicular noise

An alternative method of speed detection is presented based on the Doppler effect in vehicular noise. A procedure is developed to correlate the noise frequency spectrum as the vehicle approaches an observer with the spectrum as it moves away. Limitations of the technique are evaluated using empirical data obtained under typical traffic conditions. These results demonstrate that the Doppler shift can be extracted from automotive noise and related to the vehicle's speed. Although sources of inaccuracy are significant at lower speeds, a resolution of ±5 percent was easily achieved at 60 mph. Such a technique may be found useful in large scale traffic speed and density monitoring systems.