Is traffic congestion overrated? Examining the highly variable effects of congestion on travel and accessibility (original) (raw)
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Congestion and Accessibility: What's the Relationship?
… Research Board 88th …, 2009
This project conceptually and empirically explores the complex relationship between congestion and accessibility. While congestion alters individual access to opportunities, its effects vary significantly across people, places, and time -variations that remain relatively understudied. This report begins by proposing a conceptual framework with three components. First, congestion can constrain mobility and thus indirectly reduce accessibility.
THE SPATIAL AND GENTRYFING EFFECTS OF TRAFFIC CONGESTION by JOSEPH RANDOLPH NICHOLSON
2013
by JOSEPH RANDOLPH NICHOLSON (Under the Direction of Richard W. Martin) ABSTRACT Urban economic theory suggests that rising levels of traffic congestion will lead to smaller, more compact cities with residents living closer to the central business district (CBD). If the value of time lost commuting increases with income then high-income households should experience a stronger pull to the CBD than low-income households. These essays use data on traffic congestion in U.S. cities between 1980 and 2000 to test whether the extent to which highincome households’ location within the central cities of U.S. metropolitan areas was affected by traffic congestion levels. Then test the extent to which high-income households are moving into gentrifiable neighborhoods as they disburse throughout the city center due to increases in traffic congestion levels. Independent metropolitan level measures of traffic congestion find statistical significance with respect to the location of high-income househ...
Not So Fast: A Study of Traffic Delays, Access, and Economic Activity in the San Francisco Bay Area
2016
The San Francisco Bay Area regularly experiences some of the most severe traffic congestion in the U.S. This past year both Inrix and the Texas Transportation Institute (TTI) ranked the Bay Area third only to Washington D.C. and Los Angeles in the time drivers spend stuck in traffic. The TTI estimated that traffic congestion cost the Bay Area economy a staggering $3.1 billion in 2014 (Lomax et al., 2015). Such estimates are based on the premise that moving more slowly than free-flow speeds wastes time and fuel, and that these time and fuel costs multiplied over millions of travelers in large urban areas add up to billions of dollars in congestion costs. But while few among us like driving in heavy traffic, do such measures really capture how congestion and the conditions that give rise to it affect regional economies? This study explores this question for the San Francisco Bay Area by examining how traffic congestion is (i) related to a broader and more conceptually powerful concept...
Journal of Transport Geography, 2022
Recent transport equity literature suggests that accessibility analyses should move beyond mapping of the uneven patterns of access to opportunities. Instead, this literature proposes a sufficientarian approach, according to which all individuals are entitled to a minimum level of accessibility. In line with this approach, in this paper we ask: "What are the spatial patterns of accessibility insufficiency in U.S. metropolitan areas?" We use the Accessibility Fairness Index developed by Martens (Martens, K., 2017. Transport justice: Designing fair transportation systems. Routledge) and others to measure accessibility insufficiency. This index accounts for both people's accessibility shortfall compared to a sufficiency threshold and the number of people affected by these shortfalls. We limit our analysis to 49 of the 50 largest U.S. metropolitan areas and to people particularly reliant on transit, as they are especially likely to experience insufficient accessibility. We analyze first the spatial patterns of accessibility insufficiency for all 49 metropolitan areas jointly, for sufficiency thresholds ranging from 1% to 50% of average regional car-based accessibility. We find that accessibility insufficiency among people relying on transit is strongly concentrated in the first 10-30 km ring around the metropolitan core, with a more dispersed pattern only prevalent for the lowest 1% threshold. Next, we compare the 49 regions using only the 10% sufficiency threshold. Results show that most regions have a strong concentration of accessibility insufficiency in the urban cores and inner suburban ring. Urban densities in these clusters are relatively high, underscoring the favorable conditions for introducing efficient transit service. We conclude that accessibility insufficiency is not merely an issue of far-flung exurbs and the metropolitan fringes, but just as much a problem affecting the large transit reliant population in the urban cores and inner suburban rings. This underscores the possibilities for addressing the issue through increased and targeted investments in high-quality transit systems and transit-corridor urban densification.
International Journal of Environmental Research and Public Health, 2019
This research examines whether individual exposures to traffic congestion are significantly different between assessments obtained with and without considering individuals' activity-travel patterns in addition to commuting trips. We used crowdsourced real-time traffic congestion data and the activity-travel data of 250 individuals in Los Angeles to compare these two assessments of individual exposures to traffic congestion. The results revealed that individual exposures to traffic congestion are significantly underestimated when their activity-travel patterns are ignored, which has been postulated as a manifestation of the uncertain geographic context problem (UGCoP). The results also highlighted that the probability distribution function of exposures is heavily skewed but tends to converge to its average when individuals' activity-travel patterns are considered when compared to one obtained when those patterns are not considered, which indicates the existence of the neighborhood effect averaging problem (NEAP). Lastly, space-time visualizations of individual exposures illustrated that people's exposures to traffic congestion vary significantly even if they live at the same residential location due to their idiosyncratic activity-travel patterns. The results corroborate the claims in previous studies that using data aggregated over areas (e.g., census tracts) or focusing only on commuting trips (and thus ignoring individuals' activity-travel patterns) may lead to erroneous assessments of individual exposures to traffic congestion or other environmental influences.
Urban Studies, 2006
The paper explores relationships between seven dimensions of land use in 1990 and subsequent levels of three traffic congestion outcomes in 2000 for a sample of 50 large US urban areas. Multiple regression models are developed to address several methodological concerns, including reverse causation and time-lags. Controlling for prior levels of congestion and changes in an urban area's transport network and relevant demographics, it is found that: density/ continuity is positively related to subsequent roadway ADT/lane and delay per capita; housing centrality is positively related to subsequent delay per capita; and housing-job proximity is inversely related to subsequent commute time. Only the last result corresponds to the conventional wisdom that more compact metropolitan land use patterns reduce traffic congestion. These results prove two points: that the choice of congestion measure may substantively affect the results; and that multivariate statistical analyses are necessar...
The role of congestion of transportation networks in urban location and travel choices
Transportation, 1987
Congestion of urban transportation systems results from an equilibrium of location and travel choices with generalized travel costs which increase with vehicle flows as well as other factors. The use of network equilibrium concepts in analyzing urban policies and evaluating alternative plans is examined. Issues arising in the use of network equilibrium models are described, and formulations of urban network prediction and design models are explored.
TRAVEL TRENDS IN U.S. CITIES: EXPLAINING THE 2000 CENSUS COMMUTING RESULTS
As cities grow, what happens to urban form and how does that change traffic conditions? How does growing traffic affect urban structure? These questions have received considerable theoretical and empirical attention over the last 25 years. They relate to the NIMBY debate, which associates most new development with traffic problems. Yet, until recently, substantial evidence tended to show that urban growth did not lead to "traffic doomsday". These findings contradicted the standard urban model and were surprising because roads are mainly unpriced and perceived as a significant market failure. Many researchers explained the rise of suburb-to-suburb commuting (and the dispersion of employment) as a traffic "safety valve". In that case, suburbanization was more a solution than a problem. On the other hand,, recently released findings from the 2000 Census show an increase in average commuting times that is difficult to reconcile with the earlier findings. What had cha...
Suburban Transport Behavior as a Factor in Congestion
Transportation Research Record, 1989
Suburban congestion is among the most pressing transportation problems in large urban metropolises. One of the major causes of this problem is the changing transport behavior of people, created by a series of complex social, economic, technological, and cultural changes. Rapidly developing suburbs are a focal point for congestion in part because they are at the forefront of these changes. A conceptual framework has been established for identifying the channels through which various phenomena affect individuals and households, their orientation in life, and the decision-making process that results in manifest transport behavior. Several national trends in household structure, location patterns, incomes, life-styles, social values, and norms, as well as in technology, are identified in this paper, and their effect on transport behavior is explored. To explore differences in demographics, household structure and commuting patterns among the central cities and growing and stable suburbs...
Accessibility, Travel Behavior, and Urban Form Change
Accessibility is a central concept for urban planning both from theoretical and practical perspectives. Theoretically, accessibility is a major driver of patterns of land value and residential density in metropolitan urban regions. Practically, planning for accessibility offers the opportunity to shift away from transportation planning's historic focus on mobility (speed) and towards a focus on greater land use-transportation integration. This dissertation takes as its premise that transportation planners ought to be planning for higher accessibility and traces some of its implications. Does higher regional accessibility lead to the travel patterns that planners and travel behavior researchers expect? How are US metropolitan regions performing with regard to an accessibility-based performance benchmark over time? There is broad consensus among transportation researchers that accessibility measures indicate the ease of access to opportunities across space. Theoretically, we expec...