Wavetronix SmartSensor HD (101-0415) - User Guide User Manual

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INTRODUCTION

• SMARTSENSOR HD USER GUIDE

ample, sensors mounted on gantries have successfully met customer requirements when

using a 3-foot extension arm to laterally separate the sensor from the structure. Please

talk with a Wavetronix Technical Support representative about your specific situation.

Mounting Height – The mounting height should be based upon the offset from the

lanes of interest. For each offset, the minimum, maximum, and best heights are shown

in Table 1.1, found in Chapter 1. In general, the range of recommended heights is be-

tween 9 and 50 ft. (2.7 to 15.2 m).

Mounting Offset – The minimum recommended offset (distance from the sensor to

the edge of the first lane of interest) is 6 ft. (1.8 m).

Arterial Locations – Sensor sites on arterials or other roadway segments with regulat-

ed stop lines should be selected at midblock positions to increase accuracy by avoiding

positions at which vehicles are often stopped in front of the sensor.

Freeway Locations – The SmartSensor HD is often used at permanent ATR (auto-

matic traffic recorder) stations. The number of stations along a single roadway and the

distance between stations should be selected to achieve adequate levels of statistical

confidence. Permanent ATR stations, which are selected to cover interstate, principal

arterial, and other national and state highways, are used to establish seasonal adjust-

ment factors for count data from temporary collection sites (see Figure I.1).

Roadway

9–50 ft.

6 ft.

min

(see

mounting

guidelines)

Figure I.1 – Portable (left) and Permanent (right) Sensor Stations

Cable Lengths – Ensure that you have sufficient homerun and sensor cabling. Cables

can be as long as 600 ft. (182.9 m) if they’re using 24 VDC operation and RS-485 com-

munications; for longer connections, alternate wired and wireless options should be

considered.

Signaling Delay – After a vehicle passes in front of the sensor there will be a slight

delay before the data for that vehicle is sent from the sensor. In a time-sensitive ap-

plication—for instance, to supply a dynamic message sign with per vehicle warning

messages—it will be necessary to ensure the sensor is sufficiently far upstream from

the sign that the system has time to collect the data, process it, and send it to the sign

by the time the vehicles reach the problem area. For specifics about signaling delay,

see Appendix E.