Speed Measurement Flashcards
(35 cards)
85th Percentile
The speed at or below that 85 percent of drivers travel on a road segment
Basic Speed Law
316.183
Absolute Speed Law
Speed limit that is in force at all times regardless of enviromental conditions.
Benefits of Speed Enforcement
Save Lives, Prevent Injuries, Reduce Crashes
Methods of Measuring Distances
Selecting methods of measuring
Minimizing site obstructions
Selecting reference points
Measure Speed Accurately
Minimum distance is 300 ft
Straight line not a curve
Basic Speed Equation
Speed = distance divide by time
Parallax
Apparent movement of a fixed object when the viewer changes his or her position
Doppler Principal
Relative motion is motion towards or away from the Radar
Frequency of a radar signal changes due to relative motion
Amount of frequency change is dependent upon the speed of a vehicle
Relative Motion
Motion toward or away from the RADAR
Radar Units Decision Process
Reflective capability
Position
Speed
How the Dopler Principal applies to stationary RADAR
As the target approaches the signal frequency increases
As the target recedes the signal frequency decreases
The stationary angular cosine effect
Angle created between the vehicle and the radar
More angle lowers the speed reading
Factors Affecting Stationary Radar
Scanning effect - rapid swinging of radar unit causes incorrect reading
Panning Effect - Pointing the antenna at the counting unit causes incorrect reading
Tracking History Stationary Radar
Visual Estimation of target speed
Audio Doppler
Target Speed Display
Moving radar
Uses Doppler principle to determine speed
Transmits one signal but monitors many reflected signals
Processes two reflected signals and determines two speed reading
(Low freq and High freq)
Moving Angular Cosine Effect
Vehicle approaching towards or receding from a radar could create lower than actual speed
Moving Cosine lowers the patrol speed reading and raises the target speed reading
Completing A Tracking History
Visual estimation
Audio Doppler
Target Speed Display
Patrol Speed Verification ( moving radar only)
Direction Sensing Radar Device
Determines if the signals frequency is higher or lower than the transmitted frequency
Reflected signal is higher, vehicle is approaching
Reflected signal is lower, vehicle is moving away
Radar range = Radar sensitivity
adjusting the radar sensitivity is to eliminate unwanted interference
Proper device setup
Antenna - Box - Current
Radar Device Testing
Operator is responsible to twice daily before and after shift
Theodore Maiman
Made the first laser
LASER
Light
Amplification
Stimulated
Emission
Radiation
