NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
Volume I: Background, Methods and Tests
Literature Review and Industry Assessment
Transportation professionals have been enamored with the potential uses of Global Positioning System (GPS) data ever since GPS became fully operational in 1995. Early GPS-enhanced household travel surveys, such as the 1996 FHWA Lexington Pilot Study and the 1997 Austin Household Travel Survey, have led the way in evaluating GPS use in travel surveys (Battelle Memorial Institute 1997; Murakami and Wagner 1999; Casas and Arce 1999). These initial studies were hindered by the U.S. government’s intentional degradation of GPS’s positional accuracy (known as selective availability). Selective availability was eliminated in early 2000, thereby accelerating the rapid development and implementation of a wide range of commercial, consumer-oriented, location-based services (LBS) and supporting GPS devices.
Over the past 11 years, more than 25 household travel surveys (HTSs) conducted within the U.S. have used GPS augments to help assess the level, breadth, and magnitude of travel underreporting or misreporting by the large diary-based reporting sample. And, with each survey, GPS sample sizes have steadily increased, with some of the most recent surveys involving the deployment of GPS data loggers to thousands of households, either with large subsamples (e.g., New York City, Atlanta, and California) or with the entire surveyed population (e.g., Cincinnati, Cleveland, and Jerusalem). Over this same time frame, consumer-based GPS products, such as stand-alone or in-dash personal navigation devices (PNDs), GPS-enabled smartphones, and fleet tracking systems [e.g., automatic vehicle location (AVL) systems] have led to the creation of large-scale GPS data sets that can be mined or translated into detailed travel behavior information. In addition, other fixed-location approaches to tracking personal travel, such as those supported by Bluetooth, radio frequency identification (RFID), and mobile phone tower technologies, offer alternative methods for providing some level of travel behavior information.
The combination of these large-scale GPS travel survey data collection events, the increasing availability of large consumer-based GPS data sets, and ongoing studies evaluating the use and benefits of fixed-location sensors have led to many discussions within the transportation community about the roles, advantages, and disadvantages of various GPS data sources for transportation planning and modeling, as well as for other travel behavior research initiatives. Given the need for more data to support a wide range of transportation planning and modeling activities, combined with ongoing budgetary constraints, the time has come to clearly and objectively evaluate the multiple sources of GPS data that could be leveraged and used for transportation planning beyond the traditional application area of travel time and speed studies.
Volume II: Guidelines
The guidelines provided in this document describe the capabilities of Global Positioning System (GPS) data as they relate to transportation planning and specifically to improving the understanding of personal travel behavior. This guidance is intended for transportation planners and researchers who are considering the use of GPS data for travel behavior analysis and would like to jump-start their efforts with the foundational knowledge and recommendations described in this research. As part of this guidance, examples of successful GPS data processing techniques and information on key processing and analysis issues are provided. These steps can be followed regardless of the GPS data source (i.e., travel survey, other field data collection, or data purchased from a third party).
It should be noted that this document is not intended to be used as a step-by-step manual. Instead, it has been developed to facilitate the use of GPS data for transportation planning purposes in an ever-changing environment where new technologies, techniques, and data products are constantly being introduced. Figure 1 depicts the organization of topics that are included in this guidance document.
The creation of this guidance document follows the completion of two core tasks: (1) a comprehensive literature review and industry assessment, and (2) testing and implementation of the most promising GPS data processing techniques; details of these tasks can be found in Volume I of this report. These first two tasks provided in-depth analyses and assessments that are briefly referenced here; readers interested in more background information and details of the testing methods and findings should refer to Volume I. Furthermore, GPS technology, data availability, and recommended uses are highly dynamic topics. To counter this and ensure that this guidance maintains relevance, the discussion contained herein targets key concepts, techniques, and findings that are not tied to specific GPS data or specific products.
The Roles of GPS Data in Travel Behavior Research and Modeling
The Global Positioning System was designed by the U.S. Department of Defense in the 1970s as a navigation aid for the U.S. military; it became fully operational in 1995. Nonmilitary and consumer uses of GPS were envisioned from the start. Beginning with a 1996 trial of GPS data collection for transportation planning uses sponsored by the FHWA in Lexington, Kentucky (Battelle Memorial Institute 1997), the use of GPS technology has become increasingly widespread within the transportation field. This can be credited to ever-increasing computer power and storage capacity and the ensuing proofs of concept using GPS data to advance a range of research topics, including travel behavior, route choice, destination choice, and travel speed. A GPS approach for transportation planning data needs offers the benefits of highly precise location, time, and speed data obtained via passive and objective methods.
The promise of these benefits has allowed researchers and practitioners in transportation planning to explore and implement a wide array of practical applications. Of particular interest to travel behavior researchers are GPS applications in traditional household travel surveys (HTSs) and the potential uses of consumer-based travel behavior data products. Other transportation planning areas, such as congestion management, freight/goods movement, real-time traffic information, and asset management, have also used GPS in some manner but are not discussed in detail in this report.
The use of GPS data in transportation research is an increasingly important tool in a researcher’s toolkit. Survey tasks that were once accomplished with pencil and paper are now done passively and accurately through the use of GPS technology and systematic data management practices. As this knowledge is passed on to practitioners and they experiment with this technology for the first time, it is important to be familiar with its accepted uses, limitations, and pitfalls. An overview of some of the more promising transportation planning application areas is presented next to provide context for the following guidance provided on GPS data sources and processing methods. Readers interested in more details of these application areas should refer to Volume I. In addition, researchers curious about how GPS works should refer to “Defining GPS and GPS Capabilities” (Wolf 2004).
About the National Cooperative Highway Research Program
A forum for coordinated and collaborative research, the National Cooperative Highway Research Program (NCHRP) addresses issues integral to the state Departments of Transportation (DOTs) and transportation professionals at all levels of government and the private sector. The NCHRP provides practical, ready-to-implement solutions to pressing problems facing the industry…The NCHRP is administered by the Transportation Research Board (TRB) and sponsored by the member departments (i.e., individual state departments of transportation) of the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration (FHWA). Individual projects are conducted by contractors with oversight provided by volunteer panels of expert stakeholders.