Preproduction Prius PHEV motoring along San Diego coast.
Understanding the Hybrid Rebound Effect
By Bill Moore
Not long after the introduction of the first hybrids, critics began to warn that giving drivers the ability to drive further on a tank of fuel would only encourage people to drive more, creating just as much pollution and adding to traffic congestion. Were they right?
P> The research into the hybrid 'rebound' problem began on Dr. Neha Khanna's front porch in upstate New York. She and one of her students, Dr. Michael Delgado, who would later co-author their research paper, noticed the increasing number of Toyota Priuses on the street over the course of the summer. Were they witnessing the real world manifestation of the rebound phenomenon, they wondered.
The "hybrid rebound" effect postulates that owners of vehicles that get superior fuel economy -- on the order of up to 90% in the case of gasoline-electric hybrids like the Prius -- will take advantage of that and drive more miles. The net effect might be to negate any fuel savings and air pollution reduction gains, as well as increase congestion as more vehicle miles are driven relative to a standard, non-hybrid gasoline automobile.
Exacerbating the issue, because a car like the Prius is so distinctive in styling, it becomes a badge of honor for the owner, who depending on their personal character quirks, may chose to driven it even more to proclaim their environmental values.
The summer porch discussion would lead, some years later to a joint research paper co-authored by Khanna and Delgado with Dr. Shanxia Sun as the lead author. Entitled "Hybrid Vehicles and Household Driving Behavior: Implications for Miles Traveled and Gasoline Consumption," the 39-page research paper concludes that, yes, hybrid owners do drive the cars more than a similar individual with a non-hybrid vehicle, but…
The difference is so negligible as to be nearly irrelevant: an estimated 3% more miles. Equally important, they found the "prestige" effect of showing off your green credentials by driving a hybrid is, as far as their analysis of the data can determine, virtually non-existent.
In this 30-minute interview with EV World, Drs. Sun and Khanna discuss how they arrived at their conclusions, which are extracted from a comprehensive analysis of hundreds of thousands of responses found in the US Department of Transportation's 2009 National Household Travel Survey. Sun, Khanna and Delgado's paper was presented this week at the 2017 Agricultural & Applied Economics Association Annual Meeting in Chicago, Illinois.
You can listen to the complete interview using the embedded player below or download it to your favorite MP3 player. Limited copies of the paper can requested from Dr. Sun and Dr. Khanna. Note: Michael Delgado was ill at the time of the interview.
Originally published: 01 Aug 2017
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