Testing for the Significance of Induced Highway Travel Demand in Metropolitan Areas

Abstract

The theory o f induced growth in vehicle travel hypothesizes that highway improvements which add capacity to a specific corridor or regional transportation network will attract increased levels of vehicle traffic. This relationship of highway capacity to travel demand is an important consideration when evaluating how effective highway expansion alternatives will be in solving transportation problems. Two different but complementary empirical studies were conducted to quantify the effect of highway system improvements on travel behavior. In the first study, I apply ordinary least squares regression models to estimate travel demand elasticities with respect to travel time using travel survey data from the 1995 Nationwide Personal Transportation Survey. This is one of a very few research studies to use disaggregate household-level travel data. Travel time elasticities of-0.3 to-0.5 were found, after accounting for the effects o f household size, income, population density, and household employment. These results suggest that capacity additions that reduce travel time by 10 percent will increase vehicle-miles of travel by 3 to 5 percent. My second study investigates geographic differences in travel behavior before and after highway capacity was expanded in the Dallas-Fort Worth metropolitan area. Calibrated travel model data from 1984 and 1995 were used. This ix Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission. analysis is unique in that it applies three statistical research designs to quantify the effect of capacity expansion on induced demand for travel using a before-and-after case study approach. The three techniques, namely analysis of covariance, difference-indifferences, and OLS regression on travel changes from 1984 to 1995, produce similar results. After controlling for changes in number o f households, income, and population density, total weekday vehicle-miles of travel and daily trip productions were found to increase by approximately 20 percent and 7 percent, respectively, in survey zones that had undergone significant capacity additions versus zones that remained largely unchanged over the 11-year period. Overall, the results of this research provide evidence that highway capacity improvements generate additional demand for travel. These induced demand effects should not be ignored by transportation planners and policy makers when evaluating highway system investment alternatives.

Road Expansion, Urban Growth, and Induced Travel:A Path Analysis

“…In that some of this travel increase represents route diversions, the "induced demand" elasticity of newly produced VMT is likely even smaller. These results, which are more in line with those of several recent disaggregate, person-level studies of induced demand (Strathman, et al, 2000;Barr, 2000), suggest that past estimates of induced demand derived from lane-mile elasticities have overstated near-term impacts.…”

Induced travel demand: Evidence from a pseudo panel data based structural equations model

“…Axhausen 6 2.0 Literature review Goodwin (1992Goodwin ( , 1996, Noland and Levinson (2000), Graham and Glaister (2004) and Goodwin et al (2004) provide overviews of known income, price and supply elasticities of car ownership and demand for transport services, measured in vehicle miles travelled. Similar analyses can be found in the works of Oum (1992), Cerwenka and Hauger (1996), Cairns et al (1998) de Corla-Souza andCohen (1999), Lee et al (1999), Barr (2000), Fulton et al (2000), Noland and Cowart (2000), Noland (2001) and Cervero and Hansen (2002). Fröhlich (2003) provides a literature review of models treating the effects of increased road supply.…”

An Induced Demand Model for High Speed 1 in UK

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