Are We There Yet?: The Story of Carpool Lanes in Southern California

By Jessie Levin (PO ’18), Staff Writer

If you are like the average American, you probably spent forty-two hours of your year sitting in traffic.[1] Via a simple, back of the envelope calculation, this results in eighty days stuck in traffic during an average person’s working years. Of course, these numbers are averages and do not fully show the full picture of commuters in densely populated areas such as New York and Los Angeles. In this paper, I will briefly explore the history of High Occupancy Lanes (HOV) lanes globally and domestically. I will then use California as a case study for the efficacy of HOV lanes. I will measure the effectiveness of High Occupancy Vehicle (HOV) lanes in meeting the goals of streamlined traffic, increased public uptake of ridesharing, and reduced emissions. This paper will explore California AB 544, the most recent California legislation surrounding HOV lanes, as a solution to HOV lane challenges. I will conclude with additional suggestions such as encouraging non-traditional commuting methods (bicycle, telecommuting, or transposed working hours) for California and other states to consider when moving forward with future HOV lane legislation and implementation.

1. The History of HOV Lanes

HOV lanes are special driving lanes that are designed to reduce the number of cars on the road while carrying the same (or more) number of passengers. While the minimum person requirement varies by location and time of day, the vehicle needs to have at least more than one passenger other than the driver.[2] If one uses the lane improperly, they will be fined. These fines range from $50 in Texas and a minimum of $490 in the state of California.[3]

The concept of HOV lanes were first introduced in the late 1960s in the greater Washington DC. Metro area. In 1969, the Henry G. Shirley Memorial Highway gained a bus-only lane to attempt to alleviate traffic.[4] While some HOV lanes did arise in the 1970s, it was not until the 1980s that they began to explode in popularity due to the implementation of various programs which supported carpools.[5] Currently in the US, there are 126 HOV lanes in operation which are operated by either state or regional departments of transportation. [6]

All HOV lanes are not the same. In the United States, a majority (fifty-four percent) of HOV lanes are concurrent, which means that operate in the same direction as and adjacent to existing traffic.[7] The rest of the lanes are bus only shoulder lanes, one-way urban arterials, reversible flow, separate roadways, or bus only curb lanes.[8]

HOV lanes are not the only method of traffic management. Other forms of traffic management lanes include High Occupancy Toll (HOT) lanes and Inherently Low Emission Vehicle (ILEV) lanes. HOT lanes are a combination of traditional HOV lanes and toll lanes so cars with the minimum required people can drive in these lanes for free or a reduced price and single drivers can pay a fee to avert traffic. In some cases, the toll rates are pre-set according to the time of day.[9] In some places, such as Washington state, the tolls are determined based on the current traffic conditions and are collected via electronic transponders.[10] ILEV stickers allow qualified alternative fuel vehicles (regardless of their occupancy) to use the HOV lanes. These stickers are present in ten states: Arizona, California, Colorado, Florida, Georgia, Hawaii, Maryland, New Jersey, New York, North Carolina, Tennessee, Utah, and Virginia.[11]  Some qualified alternative fuel vehicles include hydrogen fuel cell, clean natural gas, and 100 percent battery electric fuel sources.[12] While both of these options are present in California, in this paper I will focus on the traditional HOV lanes that can also be found in other states.

2. HOV Lanes in the State of California (and why CA is a good case study)

In 1970, the first HOV lane, a bypass lane on the San Francisco- Oakland Bay bridge, appeared in California.[13]  Bypass lanes, similar to separate roadways previously mentioned, are roadways that are designed to completely avoid highly congested areas.[14]

In Northern California, the HOV lanes are operational on weekdays during rush hours (6 am -10 am and 3 pm to 7 pm). Any other time, the lanes are open for all to use. On the other hand, in Southern California, HOV lane restrictions are in affect 24/7 and the lanes are separated by other lanes by a buffer zone. The difference could be due to the commuting culture of the respective areas. According to 2016 data compiled by the US Census Bureau, almost seventy-four percent of commuters over the age of sixteen commuted to work alone.[15] For the bay area in 2016, this number is fifty-eight percent. [16] Since Southern California has more commuters in general, it might be that stricter HOV regulations HOV are needed to control the flow of traffic.

California is an appropriate state for a case study of HOV lanes for a variety of reasons. First off, California is the world’s sixth largest economy.[17] In a way, the state acts as its own country with varied industries and political arenas. Additionally, by exploring the San Francisco Bay area and the sprawling Los Angeles metro region, we can take into account other factors that influence traffic (geography, rural, urban, mountainous, costal, ect) that are seen in other locales besides California. This will allow us to attempt to mirror conditions throughout the nation.

3. Have HOV Lanes in California Been Effective?

The California Department of Transportation uses federal standards as an effectiveness guide. One standard is minimum speed requirement. A HOV facility is considered to be degraded if traffic fails to flow more than forty-five miles per hour ninety percent of the peak commuting time throughout the entire HOV facility segment.[18] So, even if there is a segment that is always slow, as long as the rest of the facility is able to move smoothly, then the requirement can be met.

It is interesting that although the environmental impacts of HOV lanes are expected and lauded, the federal government has not published emission reduction standards in 23 U.S.C. 166. This could be due to the regional nature of pollution or due to the fact that it is hard to directly contribute reduced emissions to HOV lane usage. There could be other factors that influence air quality emissions.  Even without this quantitative standard, it is expected that HOV lanes will lower running and trip-end emissions.[19] Running emissions are carbon dioxide and nitrous oxide that are produced as a result of normal operations while trip-end emissions are the additional reactive organic gasses that are produced as a result of an inefficient unwarned up engine.[20]

The other HOV lane effectiveness standard is their usage as HOV lanes were designed to promote ridesharing. A federal benchmark states that HOV lanes must carry more than 800 vehicles per hour during commuting times in order to ensure that the lane is being properly utilized.[21] So, in summary, HOV lanes must reduce emissions, carry at least 800 vehicles per hour during rush hours, and ensure that traffic is flowing at least forty-five miles per hour a majority of the time.

In Southern California, almost all of the HOV lanes exceed the benchmark of 800 vehicles per hour. In fact, the average HOV lane in SoCal carries 1,200 vehicles per hour during peak commuting hours.[22] In the San Francisco Bay area, HOV lanes are also slightly exceeding this requirement. For example, the 101 in Marin carries around 900 vehicles per hour during the peak rush hour period.[23]

When it comes to managing congestion, unfortunately California’s results have failed to reach the federal benchmark. In Northern California, 58 percent of the carpool lanes did not have a minimum speed of 45 miles per hour at least 90 percent of the time. In Southern California, 68 percent of the HOV lanes failed to reach this goal.[24]  While there probably are a variety of reasons why California metro centers are not meeting this goal, the most likely reason is just that there are too many people who live around and commute via these commuting corridors. For example, in 2015, over eighteen million people called the Los Angeles Metro region home.  [25]

In the same year, almost nine million people resided the San Francisco Bay area.[26] Although this federal goal is ideal, it might not be sustainable for the populous state of California.  Interestingly, the situation is different in less populous places such as the Dallas Metro area (6.2 million population), which suggests that the sheer number of people living in a place is a detriment to these lanes.[27],[28]  A way to mitigate this would be to restrict HOV lanes so that they would be less congested and therefore move faster.

On the environmental front, California has succeeded in reducing emissions. Researchers at the University of California, Riverside have shown that HOV lanes in both Northern and Southern California produce fewer emissions than regular lanes. It is said that vehicles in HOV lanes produce about 10 to 15 percent less hydrocarbon/ nitrous oxide emissions and about thirty-five percent less CO2 emissions and due to better traffic flow in these lanes.[29] Extending from this fact, this would mean that HOV lanes lead to fewer emissions produced per traveler since the vehicles carry more people.

In a way, the state of California has reached its goals of increasing carpooling and lowering emissions rates. But, as a consequence, the minimum speed benchmark has not been met. It is almost as if these lanes are becoming too popular and must be reworked.

4. The Enforcement Problem and AB 544 as a Possible Solution  

Although HOV lanes in California are effective in incentivizing people to carpool and reduce emissions, there are problems with enforcement. Currently, the fine in California is a minimum of $490 and increases as violators repeat offences. The goal is to keep HOV lane violators under ten percent of all HOV lane traffic.[30] Carpool lanes are monitored by cameras made by the tech company Xerox that scan cars and indicates those who drive in the lane without the required number of passengers.[31]  Once the violations go above ten percent, the California Highway Patrol is notified and puts up stricter enforcement on the effected HOV lane.[32]

California has also addressed this overutilization problem on the legislative front. California passed Assembly Bill 544. Federal law grants that states can allow ILEV to use HOV lanes until 2025 as long as these vehicles register with the DMV before September 30th, 2019 and have special decals alerting others of their status. Previously, ILEV vehicles registered with the DMV can use the HOV lanes regardless of their occupancy. This bill will essentially retire the ILEV decal eligibility for HOV lane access for older ILEV vehicles. Decals issued before January 1, 2017 will be retired by January 1, 2019 therefore lowering the amount of single occupant cars using HOV lanes.

It is up to the states to ensure that their HOV lanes are meeting these effectiveness measures. They can manipulate HOT pricing, occupancy requirements, and vehicle eligibility in order to meet these measures.[33] One such recent legislation, California AB 544 affects vehicle eligibility to help better California HOV lanes.

This raises some interesting questions. First, how should the State enforce HOV violations? The California Highway Patrol need to balance the ten percent goal previously mentioned with practical realities of spending time patrolling the HOV lanes that could be used elsewhere. One proposed answer as a part of AB 544 would be to have some the fees people pay towards AB544 go towards funding part of the enforcement.[34]  Another question that is raised is how we can get people to stop cheating the HOC lanes rules in the first place. We might need to entice people to start carpooling, taking public transit, or take alternative forms of transit to work. Or, we could look at the problem from a punishment side. This is unattractive, however, as the fines are already so high and would raise the question of whether or not there could be a cap to this fine. It would be political suicide to be the party responsible for raising fines as this can be seen as classist behavior.

5. Lessons from California and suggestions for the rest of the nation

From the California case study, we have learned that there is a fine balance between underutilized and over-utilized HOV lanes. If HOV lanes are underutilized, ridesharing incentives are not effective at changing behaviors and emissions rates will not fall. Because over-utilized HOV lanes fail to allow traffic to flow efficiently and because it is not feasible nor economically and environmentally responsible to propose new lanes, states need to work with their existing lanes to balance their utilization and encourage non-traditional commuting methods such as bicycle commuting, telecommuting, or transposed working hours. These suggested methods will hopefully reduce the demand for freeway space during peak commuting hours and help address the utilization balance dilemma.

6. Conclusion

In theory, HOV lanes seem to be a solution for California’s traffic and pollution problems. In practice, both in Northern and in Southern California, HOV lanes have reached the goals of lessening pollution and – in some way – increasing the popularity of ridesharing. However, this does not come without consequence. These lanes are becoming too popular, making their main draw (faster travel speeds) disappear. In the future, California must address this issue. While AB 544 is a step in the right direction, it is too soon to tell whether it will fix congestion in these lanes. Extrapolating, this is an important concept to keep in mind when creating or addressing the effeteness of HOV lanes throughout the country.







[1] “JAMMED: How Much Time & Money Does Traffic Congestion Waste?” Jammed: The Cost of Traffic Congestion. Accessed November 11, 2017.

[2]  “High-Occupancy Vehicle Lanes.” High-Occupancy Vehicle Lanes. August 24, 2015. Accessed November 08, 2017.

[3] California, Caltrans State of. “High Occupancy Vehicle Systems.” California Department of Transportation (Caltrans Title). Accessed November 10, 2017.

[4] Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes September 2016.” Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes – Chapter 2 Concept, Background, and History. September 2016. Accessed November 09, 2017.

[5] Ibid.

[6] Ibid.

[7] Ibid.

[8] Ibid.

[9] “Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes (September 2016).” September 2016. Accessed November 01, 2017.

[10] Downs, Anthony. “Some Like It HOT: High-occupancy toll lanes work best on high-traffic roads. Without congestion, drivers have little incentive to pay the toll.” July 28, 2016. Accessed November 09, 2017.

[11] Alternative Fuel Vehicles and High Occupancy Vehicle Lanes.” Alternative Fuels Data Center. Accessed November 11, 2017.

[12] “Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes September 2016.” Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes – Chapter 2 Concept, Background, and History. September 2016. Accessed November 09, 2017.

[13] “HOV Lanes in California: Are They Achieving Their Goals?” HOV Lanes in California: Are They Achieving Their Goals? January 7, 2000. Accessed November 07, 2017.

[14] “Managed Lane Chapter for the Freeway Management and Operations Handbook.” Freeway Management and Operations Handbook: Managed Lanes – Section 8. January 2011. Accessed November 07, 2017.

[15] American Fact Finder. U.S. Census Bureau, 2016 American Community Survey 1-Year estimates means of transportation to work by selected characteristics. 2016 American Community Survey 1-Year Estimates. Prepared by Social Explorer. Accessed November 6, 2017.


[17] Respaut, Robin. “California surpasses France as world’s sixth-largest economy.” , June 17, 2016. Accessed November 7, 2017.

[18] 23 USC 166 (2010)

[19]Boriboonsomsin, Kanok, and Matthew Barth. Evaluating Air Quality Benefits of Freeway High Occupancy Vehicle (HOV) Lanes in Southern California. University of California at Riverside. March 2007. Accessed November 5, 2017.

[20] “Rule 2202 – On-Road Motor Vehicle Mitigation Options Emission Factor Methodology .” December 3, 2014. Accessed November 02, 2017.

[21] “HOV Frequently Asked Questions.” HOV (Carpool) Lanes – HOV Frequently Asked Questions. 2009. Accessed November 04, 2017.

[22] Ibid.

[23] May, Adolf D., Lannon Leiman, and John Billheimer. Determining the Effectiveness of HOV Lanes. California Partners for Advanced Transportation Technology . November 2007. Accessed November 04, 2017.

[24] Richards , Gary . “Carpool lane crackdown barely makes a dent.” The Mercury News (San Jose). June 26, 2017. Accessed October 20, 2017.

[25] “U.S. Census Bureau metropolitan population estimates –Release Date: March 24, 2016.” Dilemma X. April 14, 2017. Accessed November 8, 2017.

[26] Ibid.

[27] Beyer, Scott. “The Explosive Northern Growth Of Metro Dallas.” Forbes, July 1, 2016. Accessed November 07, 2017.

[28] Skowronek, Douglas A., Stephen E. Ranft, and A. Scott Cothron. Evaluating HOV Lanes in the Dallas Area. Texas A&M Transportation Institute . 2004. Accessed November 05, 2017.

[29] Boriboonsomsin, Kanok, and Matthew Barth.

[30] California, Caltrans State of. “High Occupancy Vehicle Systems.” California Department of Transportation (Caltrans Title). Accessed November 10, 2017.

[31] “New camera spies carpool cheaters on Interstate 15.” CBS 8, April 9, 2015. Accessed October 21, 2017.

[32] California, Caltrans State of. “High Occupancy Vehicle Systems.” California Department of Transportation (Caltrans Title). Accessed November 10, 2017.

[33] California Department of Transportation. Division of Traffic Operations . High-Occupancy Vehicle Guidelines for Planning, Design, and Operations . Accessed October 20, 2017.

[34] Richards , Gary . “Carpool lane crackdown barely makes a dent.” The Mercury News (San Jose). June 26, 2017. Accessed October 20, 2017.


Leave a Reply