April 23, 2019
Systems for Automatic Passenger Counting (APC) automatically record the number of people in public transport vehicles. This article is intended to give an overview of the different types of automatic passenger counting systems. The strengths and weaknesses of different technical approaches are examined.
A demand-oriented design of public transport systems requires a thorough analysis of traffic flows. To ensure sufficient supply of public transport it is common practice to perform passenger surveys repetitively over time.
Typical questions to be solved in this context:
Since such surveys must be carried out in a large area and over a long period of time in order to draw significant conclusions, such surveys are often accompanied by a great financial burden.
To make matters worse, even with high survey density, individual aspects that are not permanent or restricted to a small geographic area can not be captured.
To tackle these problems, there is an effort to automatically and continuously answer as many of the above questions as possible.
Over time, various approaches have been developed. Each of which with different strengths and weaknesses.
A relatively simple way to measure the number of people in the vehicle is to install a light barrier in each door. Depending on the deviation from the undisturbed state, the system recognizes whether a person has entered or left the bus. With the help of turnover per stop, the total number of passengers can be measured during a journey.
In such systems, the weakness is that simultaneous entry and exit of multiple people is often incorrectly recognized. Likewise, bicycles or strollers are a problem. Added to this are the additional costs for the sensors.
It should not be forgotten that any misjudgment of entry and exit has a negative impact on the accuracy of the total number of people. Over the duration of a trip, the error can take steadily.
An alternative way to measure workload is with pressure sensors in the seats. If a seat is occupied, the sensor in it sends a signal to the associated control unit.
Disadvantage of this method is that only the load of the seats is considered. However, especially at peak times, is often the bulk of passengers. Furthermore, the cost of such a system is relatively high because each seat must be equipped with a sensor.
The advantage of cameras is that they are similar to the human eye. Therefore, camera systems can also cover a much larger range of functions.
The disadvantage of cameras is that some passengers feel uncomfortable being filmed. It often helps to explain the meaning and scope of video surveillance as accurately as possible.
Camera systems can be used in the doors to detect fluctuation and within the vehicle for safety and occupancy.
Camera systems in doors are usually mounted in the middle of the door and film the boarding area from above. With the aid of modern image processing, it is detected whether a person enters or leaves the vehicle. Furthermore, it can be recognized whether bicycles or strollers are carried.
Security cameras are often already installed for safety reasons in many vehicles of public transport. In addition to being used as evidence in crime, the records can also be used to evaluate vehicle occupancy. Unlike camera door systems, the number of people in the vehicle is obtained directly from the camera data. This has the advantage that measurement errors do not accumulate while driving. In addition to recognizing bicycles and pushchairs, it is also possible to estimate the gender, age and occupational group of passengers based on their appearance.
The table below gives an overview of the strengths and weaknesses of each system.
|System\Criteria||Fluctuation per stop||Utilization||Detection of more features|
(Age, Gender, Occupation)
|Usage as evidence|
|beamsensors inside the doors||+||+||-||-|
|pressure sensors inside the seats||-||+||-||-|
|camera systems inside the doors||++||+||+||-|
|surveillance camera systems||+||++||++||++|
The table lists the the different types of passenger counting systems in the first column. Each system is assessed on the basis of fluctuation per stop, utilization, detection of further features and usability as evidence. The evaluation is coded with ++, + and - representing well-suited to not-applicable.
As one can see, only surveillance camera systems yield positive results in all criteria. That is why we focus on these systems.
Last but not least, it is also worth mentioning that combination of systems can be used to complement each other or to increase robustness.
Disclaimer: The reviews are the subjective opinion of the author. The results may vary from system to system and may be dependent on other factors. In case of doubt a case-by-case examination is necessary.