Excess Commuting and Job-Housing Imbalance in Warren County, Kentucky

Abstract: Excess commuting (EC) is a concept first developed by Hamilton (1982) to measure the degree of commute distance explained by the spatial separation of job sites and households. The method is applied to a smaller metropolitan area and compared to previous studies done in larger urban areas.

Methodology: EC can be defined as the portion of all workers’ commute as a whole that is over and above the minimum required by the spatial distance between their residences and the job sites. It is a “benchmark” for evaluating jobs-housing imbalance and characteristics of urban form. It is calculated via a linear programming process that swaps workers to “new” household locations in the most efficient manner by minimizing the total travel distance for all workers. In this study, we also conducted a worst-case baseline analysis by allocating workers in the most inefficient way (maximizing the total travel distance). This measure gives the commute potential of a region and is determined by both transportation network and distribution of jobs and workers.

Caitlin Hager and Jun Yan, Center For GIS, Western Kentucky University

Comparison Analysis: The analysis is conducted at TAZ level in the Bowling Green Warren County MSA using CTPP 2000 data. The above maps show the actual commutes (A), minimized commutes (B), and maximized commutes (D) by drive-alone commuters (the most common mode in small-size cities). As shown in B, a large number of shorter commuting trips is increased drastically and the cross-town trips are minimized. On the other hand, a large number of longer trips rises under maximization (D), indicating the increased cross-town trips. In addition, under optimum minimization, intra-zonal trips are increased (C) but totally eliminated under maximization. Compared with other places in U.S., Bowling Green has relatively inefficient commutes (F), with 6.47 miles actual, 4.2 miles minimum optimal, and 9.16 miles maximum optimal mean travel distance .

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Discussion: Excess Commuting (minimization) and Commute Potential (maximization) can be respectively calculated as follows:

Warren County has an EC of 35%, which means, as a whole, 35% of total current total travel distance is unnecessary under an optimal scenario. Compared to previous studies (E), EC of Boise, ID is 48%; Omaha, WI 64%; Baltimore, MD 62%; Boston, MA 67%; Atlanta, GA 57%, Warren County, as a small-size metro, has a relatively small EC, considering that Bowling Green is one of the fastest growing cities in Kentucky and it functions as a regional employment center.

Job-Housing Imbalance: Ratio of jobs to matched workers (JHB) for all and selected industries. Job-poor areas generate commutes; job-rich areas attract commutes. Blue zones indicate a low JHB; yellow - balanced; red - a high proportion of jobs to matched workers.

Reference: Hamilton, B. 1982. Wasteful commuting. The Journal of Political Economy 90(5): 1035-53.

Excess Commute PercentageIn Order of Increasing Work Trips

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Las Vegas

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Atlanta

Boston

Philadelphia

Composite Commuting Analysis (adapted from Horner 2002)

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