Here’s Everything You Ever Wanted To Know About Carpool Lanes

If you’ve driven a car through a major metropolitan area, then you’ve probably sat in rush hour traffic staring at a free-flowing carpool lane wondering whose bright idea it was to make a whole lane off-limits to single drivers. As it turns out their benefits are palpable for everyone, whether you drive a car or not, and whether you use the lane or not. Technically, the official term is high-occupancy vehicle (HOV) lane, but they’re often interchangeably referred to as carpool lanes, so you’ll see both terms used. HOV lanes were first implemented in the United States in the 1970s, but several countries around the world now use them, too. 

Carpool lanes are categorized as “managed lane facilities,” a term that also includes high-occupancy toll (HOT) lanes, express lanes, bus or truck-only lanes, and part-time shoulders. Managed lane facilities typically run parallel to normal lanes of traffic, and often share a common right of way, but are restricted only to eligible vehicles. Here I’m exclusively focusing on HOV lanes in the United States, but if you’d like to learn more about other types of managed lane facilities or toll roads, let me know in the comments. Keep reading for all the nerdy specifics about carpool lanes.

There are two primary goals of HOV lanes: to help ease traffic congestion in heavily traveled metropolitan areas, and to decrease tailpipe emissions by incentivizing road users to take buses or to carpool rather than each individual taking a personal car. The incentive for carpooling or using an HOV lane is that there are fewer vehicles that qualify to use the lane, thus allowing high-occupancy vehicles like carpools and buses to travel faster than other lanes. The efficacy of HOV lanes varies based on many factors, but in general, vehicles using the HOV lane enjoy faster commutes, fewer headaches, and increased efficiency, especially during peak traffic times.

HOV lanes benefit everybody, though, not just the drivers using them. It’s a pretty simple concept — encouraging folks to transport more passengers in fewer vehicles helps ease congestion in heavily-traveled metropolitan areas by reducing the number of single-occupant cars taking up space on the road. Beyond reducing congestion, reducing the number of vehicles on the road also reduces the amount of ozone-destroying, Earth-warming tailpipe emissions that get spewed into the atmosphere each day. To bolster the environmental benefits of encouraging high-occupancy vehicles and carpools, some states also allow single-occupant alternative fuel vehicles like EVs and plug-in hybrids to take advantage of the HOV lane too, since they contribute to fewer carbon emissions than gas-powered vehicles. A 2013 survey of California drivers showed that 59 percent of the people surveyed said the incentive of having single-rider access to the carpool lane was extremely important or very important in their decision to purchase a plug-in vehicle.

The first HOV or carpool lane in the U.S. was actually initially created as the Henry G. Shirley Memorial Busway in northern Virginia in 1969, but was later expanded to include carpools in 1973. The first HOV lanes were implemented to decrease roadway traffic congestion, as well as reduce fuel consumption by offering commuters the incentive of a dedicated, faster-moving lane of travel should they decide to carpool. The Federal Highway Administration (FHWA) provided federal funds to states that built dedicated HOV lanes beginning in the 1970s, but these early carpool lanes weren’t particularly successful at first. This was due to poor marketing and public information disseminated about the programs, and minimal adoption. That changed in the early 1990s when some studies on the efficacy of HOV lanes were published, and the FHWA released a policy statement encouraging HOV lane development.

Since then, HOV lane use was expanded to include alternative fuel vehicles regardless of their occupancy to encourage adoption of more efficient vehicles, and to further help reduce tailpipe emissions. The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users Act (SAFETEA-LU) allowed the EPA to define single-occupant low-emission and energy-efficient vehicles to use HOV lanes, though some states have differing requirements for these vehicles to access their HOV lanes.

According to the Federal Highway Administration’s Freeway Management Program, there are 105 HOV facilities across 19 U.S. states as of June 2023. Arizona, California, Colorado, Connecticut, Georgia, Hawaii, Louisiana, Maryland, Massachusetts, Michigan, Nevada, New Jersey, New York, Oregon, Pennsylvania, Tennessee, Texas, Virginia, and Washington all have dedicated HOV lanes. Some states not included in that list offer high-occupancy toll lanes, which are roads that have electronic tolls for ineligible vehicles but are toll-free for high-occupancy vehicles. There are also Express Toll Lanes (ETL), which typically charge all vehicles on the roadway a toll regardless of vehicle occupancy, but that may permit qualifying HOVs a discounted or free trip at the discretion of the operator and regional transportation oversight. Virginia and California were the first states to implement HOV and HOT lanes, and states with higher populations tend to have more miles of specialty lanes on their roadways.

California has the most miles of toll roads in the country by far with a total of 1,449.6 miles of HOV lanes. Arizona is next with 390.1 miles of HOV lane, then Washington with 189.1 miles, Tennessee with 154.8 miles, Texas with 112.2 miles, and New York with 101.7 miles of HOV lane. The remaining 13 states each have fewer than 100 miles of HOV lane, and Louisiana has the shortest mileage of HOV lane at just 1.1 miles. In total, there are 2,827.5 miles of HOV lanes across the 48 contiguous states, and a grand total of 2,877 including Hawaii’s 49.5 miles of HOV lane.

While measuring the total environmental benefits of HOV lanes is all but impossible, logic dictates that carpool lanes are a worthwhile investment for states. They encourages road users to carpool, take buses, and/or drive alternative-fuel vehicles, which all contribute to decreased tailpipe emissions and a decreased number of vehicles clogging up the freeways at rush hour. While carpool lanes often look emptier than the other lanes on the road, the number of people traveling in the lane is typically higher than the number of people traveling in unrestricted lanes. To maximize the benefits of the HOV lane, some are exclusively enforced during peak traffic times to minimize congestion when it’s at its worst.

According to the Federal Highway Association, nearly every state with HOV lanes reports that ridesharing and overall corridor person moving efficiency has increased since the lanes opened, and the environmental benefits for air quality are inherent. Other countries have followed America’s invention of the HOV lane including several European countries, Indonesia, Canada, South Korea, and Australia. Though it can be infuriating to see a free-flowing carpool lane when you’re stuck in bumper-to-bumper traffic, their existence actually makes life a little better overall. Think of it this way, carpool lanes are likely keeping thousands of cars, and more importantly thousands of potentially bad drivers off the roads each day. That’s a lot of people that you aren’t cussing out.