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Technology Overview

Types of APC technology:

  • Infrared beams
  • Treadle mats
  • Passive thermal
  • Digital cameras with three-dimensional
    vision technology software
  • Thermal imaging
  • Ultrasound
  • Light beam

Automatic Passenger Counter (APC) systems are electronic machines near the doors of a transit vehicle that count the number of passengers that enter and exit at every transit stop. APC provides transit systems with an automated method for collecting information about the number of passengers at a variety of system levels, including route, route segment, or specific transit stops by time of day and by day of the week. APC data are helpful in identifying factors that impact ridership and passenger flows.

At the system level, ridership is an important measure of success for a transit agency. Federal and state funding agencies require ridership reports. At the route level, ridership provides a general indication of the level of demand. More detailed ridership data are used by service planners and schedulers to analyze performance and to make changes at the route, trip and stop levels so that the service provided matches the demand. Time-related data, often collected in conjunction with ridership data, are used to monitor running times and schedule adherence.

The most common types of technology used in APC systems are: horizontal or vertical electronic infrared beams, mechanical treadle mats, passive thermal, digital cameras with three-dimensional vision technology software, thermal imaging, ultrasound, and light beams. Infrared beams are mounted either horizontally or vertically and directed across the path of entering and exiting passengers, counting riders when they pass the beam. Treadle mats count by sensing the pressure of passenger’s feet as they traverse the transit vehicle’s threshold. Camera-based counting systems image the entrance or part of the entrance. The sequences of images are analyzed using three-dimensional software to identify and count individual passengers.

APC technology using digital cameras

APC technology using digital cameras

APC data is primarily used to create, evaluate, and adjust schedules and run times and to plan and justify route changes. APC-generated data can also be used for National Transit Database (NTD) reporting requirements, monitoring driver performance, and determining the best places to locate transit bus stops. By looking at the data for bus stops, those with very few passengers boarding could be eliminated and those with very crowded boarding might have an additional stop added. APCs allow the automatic collection of additional information about operations, including maximum and minimum load points, entering and exiting rates, transit vehicle dwell times, door cycles, distance traveled, and vehicle average speed.

The most common reason to collect ridership and travel time data is to compile ridership data by route. Tracking ridership changes, calculating performance measures, and adjusting schedules are the three most common uses of ridership and travel time data. Most transit agencies use a combination of automated and manual methods to collect ridership data.

Typical transit vehicle APC sensor application

Typical transit vehicle APC sensor application

APCs provide a ridership and travel time database at a finer level of detail than fare box or manual counts, even for agencies with only a few APCs. The increased number of observations lends greater confidence to decisions regarding changes in service levels. An agency does not need APC units on all vehicles to establish a workable APC system, although installation of APCs on all vehicles produces a more comprehensive database. Agencies that continue to collect ridership data manually typically do so based on cost. An argument can be made, however, that manually counting ridership is costly due to the amount of staff time required for this activity.

Common Combinations

APC and automatic vehicle location (AVL) systems are the two most important technologies that every transit system should have. Integration of the various technologies and associated sensors allows individual technologies such as AVL, wireless communications, APCs, and transit signal priority (TSP) to provide benefits greater than any one technology could provide individually.

Having APCs on every vehicle of revenue service and on every door is not enough. There must be an established and tested counting procedure that is designed to correctly count and record all entering and exiting passengers.

Processing APC data often requires changes to existing data systems, such as the addition of global positioning system (GPS) coordinates for stops and an updated transit stop inventory. The establishment of defined interfaces between computerized scheduling software packages and APC and AVL systems are critical to success. For data storage and analysis, the most common changes are the addition of servers for data storage and new database software for analysis.

An APC system can also be combined with manual data collection and fare box collection. Database management and GPS tools are used to analyze APC and AVL information. Inclusion of a GPS element in the APC system is important.

Systems Planning and Fleet Management

The data processing and reporting software is the most important component of an APC implementation. An APC system does not work automatically. Procedures must be developed to match APC data to transit stops, validate data, generate standard reports, create processes for reports, and identify hardware and software maintenance activities.

Algorithms are specifically built into the APC’s software to take into account the under and over counting of passengers created by multiple passengers crossing the beam simultaneously and passengers exiting through the front door on a two or more door transit vehicle. Other APC counting technologies are similar in operation, but differ only in how the passenger’s presence is detected and counted. The accuracy between the differing APC counting technologies is nominal.

Factors to Consider


The planning department is the most common location for management of the APC system, followed by the operations department.

Automated data validation programs, provided by the APC vendor, developed in-house, or purchased from a third party, can simplify the process of converting raw APC data into usable data. A majority of agencies rely on the hardware vendor for data processing and report generation software. Problems encountered with the APC system included reporting software, data processing and analysis, data validation, and hardware problems.


Implementation of an APC system involves multiple departments within the transit agency. APC implementation is not simple, and the first year is typically the most difficult. The APC system software is a more critical component of the system than the counting technology.

Staffing can present a challenge, especially to small and medium-sized agencies. Successful implementations are characterized by close review of APC data as part of a quality assurance program. An important step in APC implementation is to ensure that the data meet the specified level of accuracy. The threshold for acceptance of an APC system should be when the level of accuracy is in the 90 percent to 95 percent range.


Components of an APC system

Components of an APC system

Integration of APC data with existing agency databases is challenging. Agency business practices and procedures may not be designed to make optimal use of available APC data.

System integration design issues can be encountered with installing APC transit vehicle equipment post factory. When possible, factory installation of APC equipment is recommended. The following issues should be considered during APC project integration with an existing transit system:

  • The transit agency should have a detailed transit stop inventory to allow for analysis of passenger activity at the bus-stop and route-segment levels.
  • Transit agency staff needs to be prepared to handle the large amount of information gathered by the APC systems.
  • Transit agency staff should prepare a route-sampling plan prior to APC system installation that specifies exactly how and when the APC-equipped transit vehicles will collect passenger data. This is important if the APC-equipped transit vehicles will be used to satisfy NTD reporting requirements or for statistical validation of data collected for other reasons.
  • Consideration should be given to the environmental conditions in which a transit system operates prior to selecting an APC counting technology. That’s because rain, snow, salt, and extreme fluctuations in temperatures may adversely affect the operation of the counting technology.
  • Consideration should be given to the degree of difficulty involved in installation and maintenance of the APC equipment.
  • It is important that the transit agency staff support the APC program to ensure that data will be properly used and that the APC units will be properly maintained.

Benefits and Costs


The primary benefits of APCs include: data can be disaggregated at the stop, segment, and trip levels; better quality of ridership data; availability of running time data to adjust schedules; and a better basis for decision making related to service decisions. APC systems collect and store extensive and statistically valid data.

Most agencies are satisfied with their APC system’s overall reliability and the accuracy of the passenger information obtained. Most agencies report that they are achieving accuracy levels of 90 percent and above regardless of the APC counting technology employed.


APC units cost about $10,000 per transit vehicle; if additional AVL equipment is needed to collect stop-level data, then the cost will increase. Annual operating and maintenance costs per APC unit are on average between $500 and $1,000. Development and installation of any software needed to analyze the APC data typically costs around $250,000.

Metropolitan Area Express (MAX) bus in Las Vegas, Nevada

Metropolitan Area Express (MAX) bus in Las Vegas, Nevada

Equipment and Implementation

It is recommended that transit vehicles be purchased with factory installed APC systems, rather than installing the APC equipment once the transit vehicle has arrived at the transit facility. A major challenge can be identifying conduits for internal routing of add-on systems not installed by the manufacturer. Standard APC equipment is not easy to install on specialized transit vehicles. Additionally, running electrical conduit to accommodate the APC equipment can take longer than anticipated.

Passenger count data records are grouped by trip, and usually stored on the transit vehicle until they are downloaded to the central facility for processing and use. The data is automatically downloaded once a day to the central software facilities located at the transit operations center.

An APC system typically can be divided into three categories: hardware, software, and transit agency staff. To collect ridership data, such as load levels and their locations on a given route, a number of APC hardware components are required:

  • Counting sensors (such as treadle mats or I-R beams);
  • Microprocessor to tabulate, accumulate, and store passenger activity data onboard the bus;
  • Internal clock in the microprocessor to determine the time that the passenger activity occurred;
  • Automatic data storage/retrieval devices;
  • Power supply to convert primary bus voltage (usually 12 or 24 volts DC nominal) to the APC system;
  • Engine sensors to register engine dwell and idle times;
  • Wheelchair-lift sensors to register wheelchair lift activity (optional);
  • Door sensors to register door openings and closings; and
  • Radio signposts or some type of global positioning system (GPS) technology (both optional) to improve the confidence in the location referencing of transit vehicles.

Operations and Maintenance (O&M)

Standard operating procedures and maintenance activities should be followed as recommended by the equipment manufacturer. A dedicated maintenance technician or group of technicians who assumes primary responsibility for hardware issues is recommended as part of the system implementation. An assessment of staff availability and skills is recommended prior to implementation of the APC system.

Optimizing the data processing and reporting capabilities associated with an APC system to obtain ideal performance at a specific agency’s operating environment may take years. Persistence is essential for meeting this challenge and achieving the desired results.


Implementation of APCs creates a need for training. Most training is needed for the information technology departments in the areas of software/computer, analytical, and hardware skills. Mechanics will also need training for installation and maintenance requirements of the APC field technology.

Agency Deployments

Agency Contact Information Number of Vehicles Context / Success of Deployment
Regional Transportation District (RTD) 1600 Blake Street
Denver, CO 80202
(303) 628-9000
Fleet of 992 buses and 172 light-rail vehicles Developed a successful ridership tracking program using APCs on 20% of their bus fleet.
Regional Transportation Commission of
Southern Nevada’s (RTC) Metropolitan Area Express (MAX)
600 S. Grand Central Parkway, Suite 350
Las Vegas, NV 89106
(702) 676-1701
10 MAX buses on this 7.5 mile segment. The 7.5 mile segment of Las Vegas Boulevard north features dedicated transit lanes, and buses with low floors, level boarding, and an APC system.
King County Metro Transit
Seattle, WA
King Street Center
201 S. Jackson St.
Seattle, WA 98104-3856
(206) 296-0100
219 of its buses are APC equipped (15% of fleet). APC system uses treadle matts and infrared sensor technology.
New Jersey Transit Corporation (NJ TRANSIT), Newark, NJ 1 Penn Plaza East
Newark NJ 07105
(973) 491-7000
The agency operates a fleet of 2,027 buses, 711 trains and 45 light-rail vehicles. APC system uses overhead infrared sensor technology on buses and light-rail vehicles.

Additional Resources


Jonathan Walker, P.E., Ph.D.
Chief Policy, Architecture, and Knowledge Transfer, ITS Joint Program Office
U.S. Department of Transportation
(202) 366-2199

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