Know in advance how many sensors you will need and where to install them. The location of sensor stations will depend on how you plan to use them: if you intend to use the sensors to detect incidents or to generate travel times, you will want to place your sensors as close together as possible; if you plan to only use the sensors for data collection, then they can be placed farther apart.
SmartSensor HD is designed to detect moving vehicles, so you will want to place your sensor where traffic is flowing. In most highway installations this won’t be a problem, but for mid-block installations, you can run into congestion problems if the sensor is placed too close to an intersection. Make sure you install your sensor as far away as possible from intersections and other sources of congestion.
Multipath can occur when there are flat structures near the sensor, such as buildings, retaining walls and sound walls. Part of the reflected signal may bounce off these structures, resulting in false vehicle detections. In the top image, part of the radar signal is reflecting off the vehicle and returning directly to the sensor (the black arrow), resulting in an accurate detection; the rest of the signal (the red arrow) is scattered and might cause a phantom detection, as seen in the bottom image. Try to choose mounting locations where there aren’t walls or buildings directly behind or in front of the sensor.
SmartSensor HD can only detect what it can see, so if something blocks the sensor’s view of the road, the sensor might miss detections. This is called occlusion. Things that can cause occlusion include trees, tall barriers and signs. Occlusion can also be a problem in areas with high truck traffic because trucks can block the sensor’s view of smaller cars. The best way to avoid occlusion is to install the sensor away from obstacles, but you can also increase the mounting height to allow the sensor to see over the obstacles.
If your SmartSensor HD faces any other radar device, including another SmartSensor HD, the signals may interfere with each other. For optimal performance, your sensor needs to be at least 70 feet up- or downstream from any facing radar device in the vicinity. It is also a good idea to put them on different RF channels; this will lessen the chances of interference.
SmartSensor HD should be placed, as much as possible, perpendicular to the flow of traffic. Normally this is easy to do, but sometimes there will be non-parallel lanes — for example, on- and off-ramps, frontage roads, or non-parallel sides of a divided highway. If you must install in such a location, the sensor’s software allows you to exclude these problem lanes.
To avoid unneeded expense, look for spots where poles and power sources are already in place. You can use most poles, as long as they fall within the height and offset requirements. If there’s already electricity in the area for luminaries or electronic signs, tapping into these may be easier than running new power lines out to the mounting location.
Overhead structures such as overpasses, bridges, tunnels, pedestrian walkways and overhead signs can cause multipathing and other detection problems. Install your SmartSensor HD at least 30 feet up- or downstream from any such structure.
Sometimes when divided highways run through uneven terrain, one side of the road may be at a higher elevation than the other. Depending on the difference in elevation, this could cause detection problems, as shown in the picture below. Try to avoid installing in areas where the difference in elevation is extreme enough that the sensor isn’t getting a good view of the entire road.
SmartSensor HD must be installed at the proper height and offset. Offset refers to the distance that the sensor’s pole is set back from the first lane of interest; if there is a frontage road or ramp that doesn’t need to be detected, it doesn’t matter in determining the offset. SmartSensor HD’s minimum offset is six feet; there is no maximum offset, but you need to make sure that all of the lanes you want to detect fall within the sensor’s 250-foot range. How high you mount the sensor will vary depending on the offset — the important thing to consider is how well the sensor can view all lanes. At least 50 percent of a vehicle must be visible for the sensor to detect it.
