
64 CHAPTER 6 LANES
Speed – Raises or lowers the speed calculated for all vehicles in each lane. e sensor
calculates the speed, and then multiplies the speed by this factor. e default is 100%.
Length – Increases or decreases the length for all vehicles in each lane. e sensor
calculates the length and then adds the length factor. e default is 0 (feet or meters
depending on sensor units used). Since the occupancy metric that is reported in the
interval data is calculated using length, a change in the length tuning parameter will
also change the occupancy that is reported. See page 69 for the equation that is used to
calculate occupancy and for a more detailed explanation.
Extension Time – Changes the extension time, which the sensor uses to prevent ve-
hicles with trailers from being broken into multiple detections. A longer extension time
will prevent this, but can lead to multiple vehicles being merged into a single detection.
e sensor automatically determines the extension time and then multiplies by this
factor. e default value is 100%.
Note
There must be a minimum of 5.5 ft (1.68 m) between vehicles in order for them to be
detected as separate vehicles. This separation requirement may increase as vehicle
speeds increase.
Direction Protection – Allows you to turn Direction Protection on or o. When Di-
rection Protection is on (default), data will be shown only for vehicles that are going
in the direction set for that lane. For example, if a lane is set for trac moving north,
any trac in that lane that may be moving south will be ignored. However, if the sen-
sor determines that most vehicles are going a direction dierent from the one that was
congured (e.g. during hurricane evacuation), the sensor will begin reporting vehicles
going all directions. Turning o Direction Protection allows SSMHD to always report
data from vehicles going both directions.
Note
If a lane has been configured to be bidirectional, Direction Protection will be disabled.
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