HOT Lanes Seen as Best Freeway Improvement
Two new studies, one academic and one by a state DOT, have assessed ways of improving freeway performance and concluded that a HOT lanes approach is the best alternative.
The Arizona DOT last November produced a report on alternative “multimodal” improvements for congested freeways. (“Multimodal Optimization of Urban Freeway Corridors,” by Brennan D. Kidd, Final Report 582, November 2006 (available at www.azdot.gov/TPD/ATRC/publications/project_reports/pdf/az582.pdf).
After a survey of what options are being explored or implemented around the country, the study then used data from an existing Phoenix-area freeway, SR 51, to model possible additions to a six-lane freeway based on data from SR 51. The alternatives were: adding a general-purpose (GP) lane each way, adding an HOV lane each way, adding a light rail transit line, adding a HOT lane each way (defined as one allowing HOV-2 to go free), and adding an exclusive bus lane each way. The study quantified changes in performance during peak periods and estimated the annualized costs to implement each one, subtracted any revenues generated, and thus came up with the net annual cost of each. The clear winner was the HOT lanes option, not just by virtue of the lowest net cost by far, but also the lowest net cost per additional person-mile in the corridor. To assuage your burning curiosity, here are those numbers:
HOT lane: 1.2 to 2.7 cents/person-mile
GP lane: 1.9 to 4.2 cents/person-mile
HOV/BRT lane: 2.6 to 5.7 cents/person-mile
Exclusive BRT lane: 6.6 to 14.7 cents/person-mile
Light rail line: 16.1 to 35.8 cents/person-mile.
The second study is a continuation of the academic work that draws on the accumulating data on America’s first HOT lanes project, the 91 Express Lanes in Orange County, California. I’ve reported previously on Prof. Kenneth Small’s very important findings on the “heterogeneity” of value of time among commuters in that corridor, and this new paper expands on that work. It’s “Differential Road Pricing, Express Lanes, and Carpools: Exploiting Heterogeneous Preferences in Policy Design,” by Kenneth A. Small, Clifford Winston, and Jia Yan, 2006.
(www.aei-brookings.org/admin/authorpdfs/page.php?id=1258)
First, the authors do some further work to quantify both value of time (VOT) and value of reliability (VOR) for people in the SR 91 corridor, as well as the range of these values (the heterogeneity). These are surprisingly large numbers, even for users of the regular freeway lanes but especially for those who choose the 91 Express Lanes. For the latter, the median VOT is $25.51 and the median VOR is $23.78. And the heterogeneity of both is larger than the median values, especially for VOR.
Next, they simulate a number of alternative policies for a freeway like SR 91—all the lanes with no toll, the express lanes as HOV only, as HOT only, as pure express toll (no HOV freebies), and several alternatives that would use high prices on the express lanes and lower prices on the general purpose lanes. Their modeling estimates who would choose which lanes under each scenario, what the travel times would be on the express and regular lanes, etc. Then they calculate the “consumer surplus” created by each option, and break that down by income quartile. In general, they find that the dual tolling model (all lanes tolled, but with premium and regular rates) provide the largest travel-time reductions, but (due to the heterogeneity of people’s VOT and VOR) at the expense of big negatives for lower-income commuters.
So then they reason: OK, the first-best policy of dual tolling produced the best congestion reduction, but the impacts on the lower half of the income distribution are unacceptable. So what might a second-best policy look like? What they come up with is a dual-toll HOT policy, under which carpools would be allowed to go free in either set of lanes, with tolls of 19 cents/mile for regular lanes and 96.5 cents/mile for the premium lanes. This simulation shows much less impact on lower-income commuters while preserving most of the large travel-time savings.
One big caution they note in the concluding pages. The greater LA area has relatively high carpooling behavior. For more typical metro areas, with about half LA’s rate of carpooling, all the alternatives perform worse on the consumer surplus measure. A pure HOT lanes policy performed best, with a pure express toll lane coming in a close second-best on consumer surplus.