One is the Loneliest Number

Recently the Reason Foundation released a thought-provoking article about the decline in carpooling and the need to convert high-occupancy vehicle (HOV) lanes into high-occupancy toll (HOT) lanes. We at Carma Technology Corporation have more than a decade working to promote and encourage the development of carpools, and while we generally agree with the author’s recommendation to expand HOT lanes, several viewpoints expressed invite further conversation.

Support for Carpooling

The author describes the noticeable decline in carpooling around the nation despite decades of federal support. We’d like to start by recognizing the initial point made: yes, carpooling is in decline. Over the past several decades the rate of carpooling has reduced to half of what it was. The reasons for this decline are numerous, but the primary reason, as discussed in a 2018 Reason piece, is a changing economy. Technology advances and a changing workplace have made our jobs and lives more dynamic. This, in part, explains why carpooling may have declined, whereas the percentage of American’s teleworking has increased.

However, it’s our belief that it has been the failure of policy leaders to embrace innovation and technology that has also led to a reduction in carpooling.

How to Support Carpooling

Let’s address the second part of the author’s opening statement regarding decades of federal support. This is where we have a stark difference of opinion with the author. Federal authority to construct HOV lanes is not exactly what we call policy support.

HOV (and HOT lanes) are incredibly important physical aspects of creating a policy environment that supports carpooling. While the author correctly describes many HOV lanes as either being too hot or too cold, the author fails to recognize that a carpool lane, whether too hot or too cold, still carries more people per lane-mile than a regular, general purpose lane. It is our hope that policy makers see moving people as a far more important metric than moving vehicles.

Supportive carpooling policies are more than support for physical infrastructure. First, there need to be policies in place to encourage and incentivize carpooling. A TRB research report 2021 found that access to an HOV lane was the primary factor leading an individual to carpool (Li 2007). HOV lanes provide an inherent time saving, but only if there is integrity. As the author correctly states, many HOV lanes do not provide time savings because they are filled with violators. However, the answer to this problem isn’t to add more vehicles, rather it’s to restore integrity and ensure that only those who should be using the lane have access to the HOV lane. We believe that the best way to do that is through automated vehicle occupancy detection, about which we will be releasing a separate paper in the near future. We also believe that, once integrity is restored, it should be possible for excess capacity to be sold to drivers who drive alone. But the key to any HOV or HOT lane is integrity and verifying occupancy. It is critical that any HOV or HOT system effectively addresses this issue. 

Effective Transportation Systems Require More Than Infrastructure

Now to deal with HOV lanes that are too cold – the author spoke of several regions that have a network of HOT lanes that effectively move lots of people and we agree with him. However, in addition to allowing solo drivers to pay for use of the HOV lanes, many of them also have in place policies and programs that create a supportive carpool environment. The HOV lanes that are too cold are too cold because they are isolated lanes, not fully connected and not supported by additional State, regional, or local efforts.

Getting people to share a ride requires more than simply laying asphalt. Seattle, Houston, LA, and others have numerous policies and programs in place that incentivize commuters, work with employers, and truly support carpooling. It’s policies like the Washington State Commute Trip Reduction law that should serve as a model for other regions and are what we call real policy support. The Washington State Commute Trip reduction policy creates an environment in which the public and private sector work together to encourage transportation alternatives -- without placing needless burdens on the private sector. According to the Washington State CTR annual reports, every dollar invested has led to $19 of private investment in alternatives. It should be noted that over the past ten years the Puget Sound has seen rapid growth, however congestion has remained largely stagnant and in some terms improved.

Given current federal fiscal restraints and the current state of our infrastructure, we believe that federal policy makers should be looking to the Washington State law, amongst others, as an example.

Our own work with a regional employer in the Dallas region shows how effective targeted programs can be. https://www.gocarma.com/corporate-rideshare  even in a car centric state like Texas.  In this project hybrid vehicles placed in suburban neighborhoods with large concentrations of Toyota employees. Through an extensive and targeted campaign, the project was able to yield an average of 3.1 occupants per vehicle per trip (to/from employment campus), almost triple the national average.  In this pilot, participants actually paid $2-3 for the one-way service (based upon route). The benefits expressed by the users include time & money savings, front row parking on campus (saving ~:10/day), productive time during commute and networking with colleagues.

Why A Supportive Carpool Policy Matters

Why should the federal government invest in a supportive carpool policy? In short, because it’s in the federal government’s best financial interest. Decades of under-investment and dependence on an infrastructure-only policy has created a transportation system that is in disrepair and cannot handle future economic expansion. In short, we have a dollars’ worth of need and a dime in our pockets. If for no reason other than necessity, federal policy-makers must look for ways to get more people through the existing infrastructure. Therefore, we respectfully recommend the following:

  • Establish  policies that encourage integrity and time-savings along HOV and HOT lanes. Agencies should begin to move away from enforcing HOV policies and instead look to verifying occupancy using automated technologies.

  • Encourage and invest in new HOT lanes and convert (where there is capacity) HOV lanes into HOT lanes.

  • Require future priced facilities that leverage  federal assistance to require HOV and time-of-day discounts.

  • Establish and fund planning, support, and incentive policies such as the Washington State CTR.

  • Create a Federal Congestion Relief program that uses funds to increase the capacity of the existing system using technology, operations and better management. 


The recommendations above match closely those of the 2013 FHWA study of casual carpooling. We are grateful to the Reason foundation for initiating such a thought-provoking piece and look forward to working with policy makers and other stakeholders to improve our transportation system.