Pneumatic Tube Counters are a low-cost, portable approach for counting vehicles. Pneumatic tubes operate by using an air switch to detect short burst(s) of air from a passing motorized or non-motorized vehicle. The data logger then uses pre-defined criteria (e.g., axle spacing,etc.) and/or algorithms to determine whether a valid vehicle type has passed over the tubes. The technology has been used to count cars and trucks for several decades, so most public agencies either have the equipment or are familiar with the technology. Pneumatic tubes have been combined with infrared sensors at locations where both bicyclist and pedestrian counts are desired.
- Federal Highway Administration (FHWA), Traffic Monitoring Guide