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Table 3. Directional Sensor Volume Comparison
Lanes Date
Manual
Count
SS 105 SS HD RTMS ATR SS HD S.M. SS 105 S.M.
Vol. Diff. Vol. Diff. Vol. Diff. Vol. Diff. Vol. Diff. Vol. Diff.
NB
9/5 1,262 1,269 1% 1,254 -1% 1,259 0% - - - - - -
9/18 806 848 5% 813 1% 830 3% - - - - - -
10/1 836 887 6% 842 1% 859 3% 843 1% - - - -
10/14 1,036 1,084 5% 1,579 52% - - - - - - 1,108 7%
10/16 922 965 5% - - 910 -1% - - 934 1% - -
SB
9/5 1,305 1,313 1% 1,305 0% 1,310 0% - - - - - -
9/18 798 807 1% 795 0% 787 -1% - - - - - -
10/1 860 873 2% 856 0% 850 -1% 863 0% - - - -
10/14 1,043 1,040 0% 1,301 25% - - - - - - 1,243 19%
10/16 856 878 3% - - 853 0% - - 878 3% - -
Notes: S.M. refers to the sign-mounted configuration
The highlighted cells represent a difference of more than 5%
A comparison of the total sensor volumes shows the SmartSensor HD to be the most accurate
of the three sensors, followed by the RTMS and the SmartSensor 105. Compared to manual
counts, the total volume inaccuracies of the SmartSensor HD, RTMS, and SmartSensor 105
ranged from 0%, -1% to 1%, and 1% to 4%, respectively (Table 4).
Table 4. Total Volume Comparison
Lanes Date
Manual SS 105 SS HD RTMS ATR SS HD S.M. SS 105 S.M.
Count Vol. Diff. Vol. Diff. Vol. Diff. Vol. Diff. Vol. Diff. Vol. Diff.
Total
9/5 2,567 2,582 1% 2,559 0% 2,569 0% - - - - - -
9/18 1,604 1,655 3% 1,608 0% 1,617 1% - - - - - -
10/1 1,696 1,760 4% 1,698 0% 1,709 1% 1,706 1% - - - -
10/14 2,079 2,124 2% 2,880 39% - - - - - - 2,351 13%
10/16 1,778 1,843 4% - - 1,763 -1% - - 1,812 2% - -
Notes: S.M. refers to the sign-mounted configuration
The highlighted cells represent a difference of more than 5%
Traffic Speed
Speed data were recorded during each comparison study to illustrate the variation among the
sensors as previously discussed. It was difficult to calibrate the SmartSensor 105 to the hand-
held radar. Although the sensor speed values remained constant during some test days,
differences between the devices were 5 mph high on one day and 5 mph low on a different day.
Eventually the sensor was calibrated to within 3-4 mph for all lanes.
The SmartSensor HD has no parameters for calibrating speed data; however, speed calibration
was not needed. On every speed check comparison between the SmartSensor HD and the
hand-held radar, all lane’s speeds were within 2-3 mph. The RTMS speed calibration was an
easy process which required the user to manually enter the speeds taken from the hand-held
radar. The RTMS then adjusted the speed detection based on the observed values. Although
the speeds were initially calibrated to the hand-held radar, an issue was observed with the
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