For effective planning, organising, budgeting and financing, transport companies need precise data on ridership – numbers of passengers, locations and times.
Analysing sales of types of tickets allows a company to measure its overall transport performance within a defined period (month, year, etc.).
However, this does not offer sufficient planning data for specific lines. Manual counts and surveys can be useful for general analyses (e.g. a comprehensive analysis of the transit network) or specific assessments (e.g. customer satisfaction), but the time and expense involved means they must remain limited to isolated activities and/or small sample sizes, or long intervals between data collection (usually five years or more).
Automated passenger counting techniques have been developed to reduce the required data-collection costs to an acceptable level. For instance, a variety of technologies have been installed at the doors of transit vehicles to count passengers – pressure-sensitive mats, photoelectric sensors and infrared systems.
These technologies have proven robust, withstanding vibrations, temperature fluctuations, and environmental stresses.
In the case of pressure-sensitive mats, passengers are counted as they place a foot onto the vehicle step; however, it is not possible to differentiate between one or several people if they step on the mat simultaneously. The mats cannot be used in vehicles without steps.
When photoelectric sensors are used, the passenger interrupts the beams of a light curtain when entering or exiting the vehicle. This system also only delivers accurate results if it can determine the direction of passage and separate people following each other closely.
Active infrared systems send pulsed infrared signals which reflect off the boarding and disembarking passengers and are detected by infrared sensors. Depending on the width of the doors, one to four transmitter/sensor pairs are usually installed. The limitations of pressure-sensitive mats and photoelectric sensors do not apply here.
Passive infrared systems use an infrared sensor to measure the heat energy radiating from the passengers; only one or two sensors must be installed per door. A digital camera and the infrared light in the door area, which is invisible to the human eye, are used to produce a three dimensional image.
By using vehicles equipped with passenger counting systems throughout the transport company's entire network, statistically significant data can be extrapolated – although the accuracy will depend on the sample size. The use of different fare-management solutions, such as be-in/be-out and check-in/check-out access control, also makes it possible to measure ridership.