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10 on use of advanced technologies at the Orange County (Cali- set (23) and the use of APC and AVL data to develop better fornia) Transportation Authority (9). Nokel and Schweiger performing models (24). describe the design and implementation of a monitoring system for passenger counts and delays and suggest impli- cations for future projects of this nature (10 ). Bertini and DATA PROCESSING El-Geneidy are among many transit researchers to examine TriMet's (Tri-County Metropolitan Transportation District As noted earlier, the ability to turn APC data into useful of Oregon, Portland) innovative use of APC and AVL data information is critical in realizing the benefits of APCs. to improve service quality and reliability (11). Rucker provides examples of how APC data are processed for use in analyzing routes and schedules (25). Hammerle et Not surprisingly, APC data are extremely useful in iden- al. describe methods developed at CTA to extract informa- tifying ridership impacts and passenger flows. Paliska and tion for use in computing service reliability indicators (8). Kolene used APC and AVL data to evaluate the effects of unscheduled stops on ridership demand; any stop that was not associated with a known stop could be assumed to be DATA INTEGRATION unscheduled (12). Golani reports on the use of APC, AVL, and geographic information system (GIS) tools to define One of the challenges of new technologies, noted in the passenger flow on a bus route experiencing chronic delays previous TCRP Synthesis 29, is the sometimes unexpected (13). Strathman et al. analyzed the relationship between effects of their implementation on an agency's data systems. transit service headway deviations and passenger loads Bolden et al. (26) reported that interfaces between bus-re- using TriMet's AVL and APC archived data, and show that lated systems can be either unreliable or nonexistent, result- excess loads are systematically attributable to headway devi- ing in difficulty in coordinating data. The authors also note ations (14). Kimpel et al. found that APC data can be used that agencies' business processes and procedures may not be for internal reporting and annual NTD reporting if there is designed to make optimal use of available data even when widespread deployment of APC technology (15). there is good technological integration (26 ). APC data have been useful in analyzing dwell time. Use of database management and GIS tools to analyze Again using TriMet data, Dueker et al. report that passenger APC and AVL data has been cited by researchers (13, 27 ) as activity is an important determinant of dwell time (16 ). Rajb- a means to make more complete use of the data. Although handari et al. examine the impact of boarding and alighting stand-alone APC systems collect a significant amount of passengers, the effect of standees, time of day, and service valuable data, integration with data from AVL systems and type on bus dwell time (17 ). other ITS applications enhance the overall usefulness of the data (28). Procuring APCs as part of a broader ITS system An exhaustive examination of the state of the art with can reduce the overall cost of APC installation (29). In a regard to advanced public transportation systems (APTS) report on a survey of eight transit agencies deploying ITS deployment noted that optimizing the data processing and technologies, Jeng suggests that the integration of these reporting capabilities associated with an APC system may technologies presents a challenge that goes beyond the tech- take years (18). Persistence is needed to cleanse and filter the nical realm. This paper also provides lessons learned in ITS data, verify route and trip attributes, and correct or remove deployment (30 ). anomalous data. Sharing data across departments is often hindered by lack of data consistency, continuity, and com- Within the transit industry, TriMet is generally acknowl- pleteness. The report also notes state-of-the-art deployments edged as one of the leading agencies in the use of APC data. that have overcome these issues. As noted earlier, several researchers have focused on TriMet as an important case study in evaluating the use of APC data in conjunction with data from AVL systems and other AUTOMATIC PASSENGER COUNTING DATA sources (11, 14 16, 31). AND MODELING The reliability and sheer volume of APC data have encour- IMPLEMENTATION OF AUTOMATIC Passenger COUNTING SYSTEMS aged researchers to use the data in modeling efforts. Several studies report on the use of APC data to develop a model to predict bus arrival times (1921). Other researchers have Marx and Bruun reported on a successful implementa- used APC data to calibrate or validate travel models. One tion of APCs as part of a broader ITS implementation at author notes that APC boarding data are far more reliable the Potomac and Rappahannock Transportation Commis- than data used to estimate the current set of boarding equa- sion (32). An interesting aspect of this report is that the tions (22). Others note the benefits of an enriched transit data benefits of advanced technologies do not accrue automati-