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Pneumatic road tube sensors send a burst of air pressure along a rubber tube
when a vehicles tire passes over the tube.
The pulse of air pressure closes an air switch, producing an electrical signal
that is transmitted to a counter or analysis software.
The pneumatic road tube sensor is portable, using lead-acid, gel, or other
rechargeable batteries as a power source.
The road tube is installed perpendicular to the traffic flow direction and is
commonly used for short-term traffic counting, vehicle classification by axle
count and spacing.
Some data to calculate vehicle gaps, intersection stop delay, stop sign delay,
and saturation flow rate, spot speed as a function of vehicle class, and travel
time when the counter is utilized in conjunction with a vehicle transmission
sensor.
Advantages
- Cheap and self-contained, the easiest to deploy of all intrusive systems,
recognized technology with acceptable accuracy for strategic traffic modeling
purposes, hence very widely used.
- Axle-based classification appears attractive, given sub-vehicle categories
are partially axle based.
Disadvantages
- Some units are not counted or classify vehicles.
- Tube installations are not durable, the life of tubes are less than one
month only.
- The tube detectors are not suitable for high flow and high speed roads.
- Units should not be positioned where there is the possibility of vehicles
parking on the tube.
- It can’t detect the two wheelers.
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