§Must
be 24 hour free-flowing speeds
–Measuring all vehicles in queues results in a lower than actual
speed distribution
–Vehicles entering or leaving the stream shall be excluded
–At least 500 feet from junctions, convergence zones and
curves
–No active enforcement prior to or during study
§Measurement
methods must not impede traffic or influence results
–Radar
devices have shown to result in 3 mph plus reduction in speed - "DetectibleÓ measurements methods influence results
–Measurement cosine angles greater than 15 degrees results not
reliable
§New
roadway surface increases speed 4-5 mph
§Trucks
on average are 3 mph slower
§Prevailing speed - 85th percentile speed
rounded up to next 5 mph
§Higher
speeds are found where higher speeds are safe
§Highest
speed roadways safest
§Every
5 years or when there is a substantive change in use
§