This type of vehicle is becoming increasingly popular in North America. We usually need two directional sensors, one GPS antenna and an on-board computer to setup a passenger counting system in lowfloor vehicles.
The directional sensors are installed above the doors, where they detect people coming in or going out of the vehicle. The sensors' signals are sent to the on-board computer, usually installed near the driver area. The GPS antenna for these vehicles is mounted internally. It is installed just below the roof, often simply stuck to the roof with adhesive or Velcro(r). The GPS antenna is connected to the on-board computer.
The on-board computer can also be connected to vehicle signals, such as the engine or the odometer. These signals are used to know when to count passengers (when the engine is turned on). Coupled with GPS data, the vehicle's signals are also used to localise stops.
The data collected in the on-board computer can be transferred manually with the Data-Collector. For automatic transfers, an infrared or radio modem is installed inside the vehicle, near a window. A similar infrared or radio modem is installed in the garage and connected to a computer where data is dumped regularly.