Dept. of Transportation
Metro Transit Division

King Street Center
201 S Jackson St
Seattle, WA 98104
Metro Online Home

Automatic Passenger Counter

Objective 1: Technical Approach

In November and December 2001, King County Metro Automatic Passenger Counter project staff conducted passenger count surveys on the demonstration coaches equipped with an infrared passenger counting system. The purpose of the survey was to compare passenger ons and offs observed by staff riding the bus with passenger ons and offs recorded by the system. The assessment focused on the performance of the demonstration equipment at the stop level, and was not intended to assess APC performance for route level or system wide passenger counts.

A sample of 1,057 bus stop records was collected from coach 2399 for the analysis. A smaller sample of 178 bus stop records was collected from coach 9024, with the data following similar patterns, but was not included in the final analysis due to low ridership.

  • APC project staff analysis indicated that the demonstration APC system had an overall accuracy of 105 percent for passenger ons and 91 percent for passenger offs, showing an overall tendency to overcount passenger ons by 5 percent, and undercount passenger offs by 9 percent from observed ons and offs.
    • This meets the current APC program specification and Smart Bus demonstration specification for overall accuracy of +/- 5 percent for passenger ons, but does not meet the +/- 5 percent specification for passenger offs.
  • APC staff also compared the performance of the demonstration equipment to other current APC program specifications, that were not among the demonstration equipment procurement specifications:
    • In stop-by-stop comparisons, the demonstration APC equipment at the back door met current APC specifications for zero allowed deviations from observed counts, but the front door equipment did not meet the specification.
    • The demonstration passenger counter equipment on both the front and rear doors met current APC specifications in +/-1 and +/-2 categories, which allow counts reported by the system to be within +/-1 or +/-2 of the observed counts at a stop.
  • In total, the demonstration equipment met or exceeded 12 out of 18 current King County Metro APC program specifications.
  • KCM APC project staff described the demonstration technology as "encouraging," with acceptable accuracy likely to be achieved by working with the vendor to fine tune the hardware and software, if the equipment were purchased for system wide implementation, rather than as a short duration demonstration.

Objective 4: Issues and Recommendations for Implementation

Stop sequence data quality issue:

In the analysis of APC data, APC project staff identified some errors in the stop data associated with the APC counts. This highlights the importance of stop sequence data quality for onboard systems implementation. One of the goals of the current Stop Information System (SIS) project is to identify areas of potential error in the current stop data process and improve the process for downstream systems.

Technical Staff Debriefing:

  • The ability to identify errors in KC Metro stop sequence data and correct them in a timely manner will be a critical implementation issue.

Assess impacts on work processes and tools:

  • In an onboard systems environment, APC post-processing will be streamlined, but the volume of data managed by staff will increase. The impact on APC staff and work processes will need to be assessed including:
    • The data quality and troubleshooting processes;
    • The required toolset for managing and troubleshooting APC data;
    • Staffing requirements.

Objective 5: Potential Long-Term Benefits

APC project staff anticipate that implementation of technology similar to the demonstration APC units would provide a number of benefits to APC data processing including:

  • Fewer repairs on APC units: The current mat-based APC system installed on the coach steps, is prone to damage from passenger foot traffic and water damage. An alternative technology such as the Smart Bus demo infrared light beam is expected to be less prone to damage in the coach environment.
  • Easier repairs, less impact on data collection: If repairs are needed, new modular equipment will allow technicians to more readily remove the broken unit and replace it with a new one.
  • Less post-processing of data: a considerable level of effort is involved in processing APC data after it has been collected from coaches. APC staff anticipate a new APC system that integrates stop data with passenger counts will streamline the process. Data quality emphasis is expected to shift to the front end of data collection to provide improved input to the process.
Updated: Sept. 2002