The basic idea behind these systems is quite simple; some type of sensing device is needed to be positioned so that it can easily and accurately read people as they board and de-board the vehicle. It becomes a little more complicated when you have to decide which type of sensing technology will work and perform the best.
Of the technologies currently available, an infrared sensing device that utilizes the combination of both an active and passive sensing element combined into one sensor head has a proven track record to be perfectly suited for the public transit market.
The combination sensor uses both an active and passive sensing technology. The passive part of the sensor is a pyro-electric sensing unit that detects the heat movement pattern of a person. Pyro-electric technology has many uses in today's ever-changing technology driven world. In this instance for APC detection the movement is detected through the innovative use of "inner" and "outer" curtains projected by the sensors. Each sensor utilizes three individual segments to create the outer and inner curtain. Movement, therefore, is detected when either the "inner" or "outer" curtain is interrupted. Depending on which curtain is interrupted first, will determine if the passenger is boarding or leaving the vehicle.
In addition, the combination sensor also uses an active sensing element, which sends an infrared light to the inner and outer curtain. As soon as somebody passes, the active sensor detects the reflection of the person. The sensor combination detects the direction and how many passengers pass though the door. The sensors are installed above the door, and the width of the doors determines if one or two sensors need to be installed. One sensor can be installed for a door up to 39-inch width. The sensors are connected to an analyzer which compiles the input from the sensors.
Issues can often arise when installing a new APC system within an existing system. Two common issues with APC system installations are:
- Finding the optimal sensor location and determining the correct door contact. This can be a little time consuming, but once the proper position and connection are finalized, the system will be ready to provide accurate data.
- Another issue is vehicles that have a door hatch that is filled with door activation mechanics so mounting an internal sensor is not feasible. The good news is that this is easily overcome with the use of an external sensor mounting bracket. Fortunately all vehicle configurations can be installed since the sensor integration is flexible due to various types of installation locations, and the setup can be defined via analyzer software settings.
Once the ridership data is collected by the APC system it is in a raw format and contained on the vehicle. To be truly useful to the transit agency this information needs to combined with other information about the vehicle and then transferred off the vehicle.
Within the system the APC analyzer holds this information and passes it to the onboard computer after the door is cycled. The onboard computer stores the count information with the GPS location for the stop. The on-board computer stores all the count information with locations until the vehicle returns to the garage or a location near a wireless access point where the data is automatically uploaded to the server.
It is best to have a vendor perform a pilot installation and only complete the fleet installation after verification of the accuracy. A preferable alternative is for an OEM installation at the factory which yields the best results and highest quality installation.
The vehicles are delivered to the agency with the APC systems already installed, and the agency only needs to conduct a quality check and test rides to verify proper functionality and accuracy.
Once buses started being equipped with APC systems and were able to collect the passenger count data automatically, a new challenge presented itself; how to get the data from the vehicle into the reporting system? Most of the early APC systems relied on the use of some form of removable media storage. This could be a floppy disc or memory card.
Unfortunately; these required manual labor to retrieve and replace, and these small devices were often lost or broken by the people carrying them around. As a result the benefits and value of implementing the APC counting system are reduced.