Is congestion the same everywhere?

Highway congestion, very simply, is caused when traffic demand approaches or exceeds the available capacity of the highway system. Though this concept is easy to understand, congestion can vary significantly from day to day because traffic demand and available highway capacity are constantly changing. Traffic demands vary significantly by time of day, day of the week, and season of the year, and are also subject to significant fluctuations due to recreational travel, special events, and emergencies (e.g. evacuations). Available highway capacity, which is often viewed as being fixed, also varies constantly, being frequently reduced by incidents (e.g. crashes and disabled vehicles), work zones, adverse weather, and other causes.

To add even more complexity, the definition of highway congestion also varies significantly from time to time and place to place based on user expectations. An intersection that may seem very congested in a rural community may not even register as an annoyance in a large metropolitan area. A level of congestion that users expect during peak commute periods may be unacceptable if experienced on Sunday morning. Because of this, congestion is difficult to define precisely in a mathematical sense – it actually represents the difference between the highway system performance that users expect and how the system actually performs.

Congestion can also be measured in a number of ways – level of service, speed, travel time, and delay are commonly used measures. However, travelers have indicated that more important than the severity, magnitude, or quantity of congestion is the reliability of the highway system. People in a large metropolitan area may accept that a 20 mile freeway trip takes 40 minutes during the peak period, so long as this predicted travel time is reliable and is not 25 minutes one day and 2 hours the next. This focus on reliability is particularly prevalent in the freight community, where the value of time under certain just-in-time delivery circumstances may exceed $5 per minute.

Title: Spatial Mismatch or Automobile Mismatch? An Examination of Race, Residence and Commuting in US Metropolitan Areas

 

With congestion continuing to grow despite valiant efforts to curtail it, and as the cost of congestion both in terms of lost personal time and reduced economic productivity continues to rise, the U.S. Department of Transportation decided to rethink the approaches the nation is taking to addressing congestion and to redirect efforts to improve results. The Department developed a bold, aggressive strategy, outlined in its May 2006 multi-prong National Strategy to Reduce Congestion on America's Transportation Network (PDF), which is often referred to as the Congestion Initiative. The first of the Congestion Initiative's tenets is to "relieve urban congestion," which further calls for the Department to enter into Urban Partnership Agreements with model cities, pursuant to their commitment to, among other things, implement "broad congestion pricing." To educate the public about the congestion problem and how broad congestion pricing is key to addressing it, the Federal Highway Administration (FHWA) developed a Congestion Pricing Primer....

A multi-scale analysis of urban form and commuting change in a small metropolitan area (1990-2000)

Journal The Annals of Regional Science

Issue Volume 41, Number 2 / June, 2007

Mark W. Horner

Abstract Issues of growth, especially the spatial nature of recent urban development and its implications for travel patterns, have received a great deal of attention. In particular, questions persist as to how the spatial distribution of workers and jobs influences commute patterns. This paper investigates changes in commuting and land use patterns using measures of jobs-housing balance, commuting efficiency and other statistics. A smaller urban area is chosen for study (Tallahassee, FL, USA)and data on its workers, jobs, and commute patterns are obtained from the Census Transportation Planning Package for 1990 and 2000. The key research questions investigated probe whether there were substantial changes in urban form and commuting over the period. A two-tiered approach is taken where change is explored at the regional and local scales using GIS, optimization procedures, and inferential statistical techniques. The results reveal the extent of the spatial changes in the study area between 1990 and 2000. Major findings included stability in urban structure over the time period, as well as a persistent strong relationship between land use and commute patterns. These results are discussed in light of their implications for other cities and for future work.

The Changing Commute: A Case-study of the Jobs-Housing Relationship over Time
Authors: Martin Wachs a; Brian D. Taylor a; Ned Levine a; Paul Ong a
Affiliation: a Graduate School of Architecture and Urban Planning, University of California, Los Angeles, Los Angeles, CA, USA
DOI: 10.1080/00420989320081681
Published in: Urban Studies, Volume 30, Issue 10 December 1993 , pages 1711 - 1729
Abstract
Commuting patterns between home and work were studied among 30 000 employees of Kaiser Permanente, a major health care provider in Southern California. The study tracked the differences between home and work location among employees over 6 years by analysing employee records and responses to a survey of over 1500 of the workers. It was found that work trip lengths had in general not grown over the 6 year period. Growth of the work force had contributed more to the growth in local traffic congestion than had a lengthening of the work trip over time. The automobile remains the dominant mode of travel between home and work for these employees, and choices of residential location were found to be based upon many factors in addition to the home-work separation, such as quality of neighbourhood and schools and perceived safety.
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Journal	Papers in Regional Science
Publisher	Springer Berlin / Heidelberg
ISSN	1056-8190 (Print) 1435-5957 (Online)
Issue	Volume 25, Number 1 / December, 1970
Category	Spatial Analysis
DOI	10.1007/BF01935821
Pages	133-150

Asha Weinstein- "The Congestion Evil: Perceptions of Traffic Congestion in Boston in the 1890s and 1920s"