While conducting aerial operations, a helicopter hovers at several different areas. One is about MM123 and the others are near both ends of the span. Look for the broad white lines that are painted on the sides of the roadway. An officer flying overhead can look at traffic and see which car is traveling faster than the general flow. Once that car reaches the first white line, he begins the stopwatch. As the vehicle reaches the second broad white line the officer then ends the timer on the stopwatch. Because the distance between the two white lines is known, converting time to speed is accomplished by looking at a chart. The overhead officer then radios officers on the ground witha description of the vehicle as well as the speed. ANYTIME you see a broad white lines painted on the side of the road for no apparent reason, BEWARE, somebody could be watching.