TRANSPORTATION RESEARCH BOARD
Bicycling and walking, or “active transportation,” are fundamental modes of transportation, but methods to monitor the traffic of these modes have been slow to advance until the last decade or so. The purpose of this document is to chronicle the most recent advancements in techniques and technology of active transportation monitoring, but it is not meant to be an exhaustive review of the field. Though written for an audience of practicing engineers, urban planners, transportation researchers, this e-circular may also be of use to citizens or activists interested in developing high-quality data on bicycling and walking. More specifically, this e-circular addresses two key objectives:
1. Identify a selection of recent advancements in bicycle and pedestrian data monitoring pertaining to both traffic volumes and behavioral data and
2. Introduce a selection of ongoing projects expected to contribute to the field of bicycle and pedestrian data.
As a TRB e-circular, this document is intended to be immediately helpful to researchers and practitioners, but only for a relatively short shelf life. As such, it does not address a detailed chronology of the field, nor offer recommendations on next steps. This document focuses on where we are now.
RAPID ADVANCEMENTS IN PERFORMANCE MONITORING
Detailed information on passenger and freight vehicles are required by the FHWA (1) and other agencies, and a variety of solutions for monitoring traffic and travel behavior have been available for motorized modes for many years. Recently, researchers and practitioners in bicycling and walking transportation have leveraged knowledge and technology in the field of traffic monitoring towards active transportation modes. This upswing in research is shown in Figure 1, which shows the results of a search in Google Scholar for the terms “bicycle pedestrian traffic count”, increasing from only about 50 related publications in 1990, to more than 1,600 in 2011. Citations in general have also increased during this period to some extent. The slight decline of citations in the year 2012 implies a first indication of a maturing field and an opportune moment to document the state of the practice and the latest science.
Two key national surveys provide a pulse on travel in the United States, but are limited at smaller geographies: the U.S. Census—American Community Survey (ACS) and the National Household Transportation Survey (NHTS). The NHTS began in 2001 as a combination of the American Travel Survey with the Nationwide Personal Transportation Survey. The NHTS is limited to a small sample of the nation, but offers a local add-on sampling for jurisdictions wishing to bolster the accuracy of results in their area. Conducted every 5 to 7 years, the NHTS provides information on all travel modes for all travel purposes. Its sample size of more than 150,000 households across the United States can be very useful for nationwide statistics, but poses significant challenges in use for local bicycle and pedestrian studies (2).
In 1960, the U.S. Census started tabulating commute mode with the question: “How did this person get to work last week?” (3). The question wording and commute mode options have changed slightly over the years, and the ACS took over responsibility for journey-to-work from the decennial census following the year 2000, the last year for the long-form questionnaire (4). This change from full census tabulation to the sampling of the ACS decreased the absolute accuracy of the commute mode question, but increased its frequency. The modern ACS provides the most publicly accessible snapshot of commute mode data in the United States on an annual basis, but it has several problems for analysis of bicycling and walking. First, the ACS only asks about one trip purpose: the journey to work. In most places, more trips are taken as a pedestrian or bicyclist for other purposes as a whole, such as school, social, shopping and recreational purposes. The modern ACS question asks “How did this person usually get to work last week?” which means that any mode other than a respondent’s predominant mode is not recorded at all. Also, the margins of error for smaller populations for a single year are rather large, limiting the usefulness of the data for many analyses. However, efforts such as the Census Transportation Planning Package add value to ACS data by offering cross-tabulations of journey-to-work with flow and demographic data.
About the Transportation Research Board
“The mission of the Transportation Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal.”