New Motor Vehicle Fuel Economy Standards, Part 5:
the evolving mission of 'high occupancy vehicle' (HOV) lanes

27 Jun 2007 in Regulatory Policy

The Washington Post recently carried a story on motor vehicle air pollution. Part of the story concerned carpooling, which normally is required for access to "high occupancy vehicle" (HOV) lanes on urban interstate highways. The story shows how the original purpose of HOV lanes -- reducing rush hour traffic congestion -- is evolving into the entirely different purposes of air pollution control and fuel efficiency. This is the predictable result of extending HOV lane privileges to solo drivers of hybrids.

The Post article ("The Air We Breathe") is a complex graphic containing several sections describing why air pollution is worse in the summer, explaining the color-coded air quality index, listing public transit agencies, and finally, comparing tailpipe emissions of nitrogen oxides from four classes of new cars: light duty hybrids, passenger cars, light duty trucks, and heavy-duty trucks.

The message of this latter comparison is clear: light-duty hybrids emit 20% of the NOx from passenger cars, 3% to 7% of of the NOx from light duty trucks, and 2% of the NOx from heavy duty trucks. (The examples given or heavy duty trucks are recreational vehicles and GM's Hummer. This is misleading. The H3 and H2 have gross vehicle weights of 5,850 and 8,600 pounds, respectively. The H3 is a light duty truck in all states; the H2 is a light duty truck in California. Better examples of heavy duty trucks would include Ford F250 and above, Chevrolet 2500HD and above, and Dodge RAM 2500 and above.)

The comparison serves to set up a second message: driving a hybrid is environmentally equivalent to carpooling:

In Virginia, solo hybrid drivers are allowed to use HOV lanes, a perk that annoys carpoolers who think hybrids clog the lanes and defeat one of the primary purposes of carpooling: getting more people in fewer cars to cut down on pollution. Three people in one car is better than three people in three hybrids, they reason. They might be right as far as congestion goes, but not on air quality.

The Post's argument begins with an invalid compound premise -- that HOV lanes were intended to reduce the number of vehicles and reduce air pollution. This is false. HOV lanes were established solely to reduce rush hour congestion. Neither tailpipe emissions nor fuel economy were factors. HOV lanes were originally called "carpooi" lanes, and the term HOV itself says nothing about fuel economy or emissions. Finally, access restrictions to HOV lanes are routinely eliminated outside of rush hour.

When hybrids (and prior to that, electric vehicles) first entered the market, proponents of these technologies used a classic "infant industry" argument to justify various subsidies on the ground that consumers would not willingly purchase these vehicles if they had to pay what they cost to manufacture. Among these subsidies were tax credits and HOV lane access. States struggling to meet their air pollution plan targets began scavenging reduced emissions from HOV lanes because that earned credit for actions which required no additional cost to implement.

As long as the numbers of electric vehicles and hybrids were small, the additional congestion they contributed to HOV lanes also was small. But now that hybrids have become mainstream, their number on the highway at rush hour has risen dramatically, and HOV lanes are becoming nearly as congested as regular lanes. This defeats their purpose, which always was to reduce congestion by rewarding carpooling. (California has capped the number of hybrids allowed to use HOV lanes to solve this new congestion problem.)

By extending HOV access to solo hybrid drivers, government has created a new constituency that can be expected to defend its preferential access. As hybrids increasingly congest HOV lanes, we predict that this constituency will seek to convert HOV lanes into "green car" lanes and carpoolers will become the interlopers.

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