TCS Daily

Hybrid Hubris?

By Iain Murray - April 29, 2005 12:00 AM

The Commonwealth of Virginia is faced with an unpleasant problem with its HOV (High Occupancy Vehicle) lanes in the highways of Northern Virginia. Designed to speed people who are willing to take the bus or carpool to their workplaces at the Pentagon or Washington, DC, they are getting clogged up and journey times are suffering. A good deal of the problem seems to have been caused by an ill-considered and possibly illegal decision to open up the lanes to hybrid vehicles. Repealing this measure would be a good start in sorting out the problem, but Virginia needs to go further.

Anyone who, like me, takes the bus in to work in Northern Virginia will have noticed the massive increase in the number of hybrid cars in the HOV lanes over the past few years. Indeed, according to counts by the Virginia Department of Transportation (VDOT), hybrids now account for 19% of all vehicles on the HOV lanes during the morning restricted period (an unscientific count of vehicles overtaking my bus on the way in to work this morning confirmed this proportion). This would not be a problem if it were not for the fact that the HOV lanes are currently operating at what VDOT calls "unacceptable levels of service at over 1,900 vehicles per lane per hour." This is five percent greater than the maximum recommended operating capacity of an HOV lane, which is 1,800 vehicles an hour. Without the hybrid exemption, the lanes would be operating at a much more acceptable 1,540 vehicles per hour.

HOV lanes have a maximum operating capacity because they need to flow at a much higher speed than normal lanes to provide the three benefits Virginia claims for them: to manage congestion, to help the State attain its clean air goals and to provide a time-savings incentive for people to rideshare. The latter incentive has led to a remarkable, spontaneous, self-ordering phenomenon known as "slugging," where drivers stop to pick up strangers at designated locations in order to travel legally in the HOV lanes. It saves thousands of "slugs" a fortune in commuting costs while getting them to work quicker than they would otherwise, and exists without any government involvement beyond a few signposts.

The hybrid exemption, then, achieves only one of the three benefits (attainment of clean air goals) but causes significant problems for the other two. The HOV lanes have become unacceptably congested and, as a result, the time savings are lessened to the extent that ride sharing (including "slugging") becomes less attractive, with attendant implications for congestion and clean air goals. One need only take a look at the vituperation heaped upon hybrids in commuting forums (such as this one) to see that the problem is widely felt.

It should come as no surprise, then, to learn that Virginia is considering ending the hybrid exemption in 2006. This would be a start towards reducing HOV congestion and achieving the benefits HOV lanes are supposed to bring. VDOT is, however, currently reviewing an even more radical solution, that of converting HOV lanes to HOT (High Occupancy/Toll) lanes, where high occupancy vehicles would still ride free but low occupancy vehicles would be able to use the faster lanes for a toll payment. The price of the toll would change dynamically, attracting or dissuading potential payees so as to ensure the most efficient use of the faster lanes. The idea is essentially combination of HOV theory and congestion pricing to create a "value pricing" approach to road provision.

HOT lanes are often derided as "Lexus Lanes," on the basis that richer people will be more willing to use them. While this is certainly the case, a 2003 study of HOT lanes in Virginia by Resources for the Future found that all income levels benefit from the conversion of HOV lanes to HOT status. The richer benefit more, but the poor still benefit. RFF calculated that the effect would be to reduce speeds very slightly on the HOV lanes but improve them enough to be significant in the normal lanes, with the result being a net welfare gain to travelers amounting to $46 million per year.

Unfortunately, the RFF study was unable to model the effect of the conversion on slugging and the possible costs implied there. As mentioned above, thousands of slugs save substantially on commuting costs by providing their services for HOV compliance. If slug drivers are attracted away to toll-paying, there will be a cost to pay. Indeed, if slugs then drive themselves, congestion could well increase. It is entirely possible that these costs will wipe out the benefits of HOT lanes. Any VDOT review that does not include an assessment of the effects on slugs would therefore be flawed.

As it stands, the HOV experiment in Northern Virginia is close to the breaking point. At least part of the reason is due to the hybrid exemption. Ending that will give the system breathing space to consider other options, such as HOT conversion. Whatever happens, Virginia must give consideration to the significant capacity constraints associated with commuting in the area. Given the area's reluctance on fiscal and environmental grounds to expand road capacity, innovative solutions will be needed. After all, the Commonwealth cannot rely on the Federal Government to cut its size so that there are fewer commuters, can it?


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