Carpool & rideshare programs

Evidence Rating  
Expert Opinion
Evidence rating: Expert Opinion

Strategies with this rating are recommended by credible, impartial experts but have limited research documenting effects; further research, often with stronger designs, is needed to confirm effects.

Health Factors  

Carpool and rideshare programs help commuters share transportation. Carpools and rideshares can be informal arrangements between individuals, sometimes called casual carpooling, or be formally arranged through dynamic ridesharing programs or other ride-matching services. Employers, along with state and local governments, often support the creation of carpools and vanpools, coordinate ridership, and provide incentives such as preferential parking for participants1

Expected Beneficial Outcomes (Rated)

  • Reduced traffic congestion

  • Reduced emissions

  • Reduced vehicle miles traveled

Other Potential Beneficial Outcomes

  • Increased mobility

  • Improved quality of life

Evidence of Effectiveness

Carpool and rideshare programs are suggested strategies to reduce traffic congestion, decrease emissions, and reduce vehicle miles traveled (VMT)1, 2, 3. Studies suggest that these programs can be cost-effective2, 3, 4, especially for longer commutes5; programs may also improve mobility and quality of life for seniors6 and reduce stress for commuters7. Overall, transit incentives can increase use of alternative transportation; however, additional evidence is needed to confirm effects and costs of carpool and rideshare programs specifically8.

Available research suggests that improving awareness, trust and willingness to ride with strangers9, 10, 11, and flexibility in scheduling may increase carpool use9, 10, 11, 12. Carpool use may also increase with incentives such as free or decreased toll rates1, 3, 13 and reduced parking prices for carpool or rideshare vehicles12, 14, 15. High gas prices12, 16 and high costs of parking for individual cars may also support carpooling12.

High occupancy vehicle lanes (HOVs) may increase carpooling and ridesharing in some circumstances; however, local context strongly influences the success or failure of HOVs and carpool or rideshare programs17

Impact on Disparities

No impact on disparities likely

Implementation Examples

There are roughly 613 ride-matching services in the US and Canada as of 2012. Many services incorporate the use of technology (e.g., internet, mobile phones, mobile apps, and social networking)18. Searchable databases support carpool and rideshare opportunities in most states; examples include eRideShare, Ridester, and Drive Less Connect19, 20, 21.

Department of Transportation offices in many states provide information on state rideshare programs; for example, Michigan and Washington22, 23. Government agencies also directly support vanpools in some states. California Vanpool Authority’s CalVans program, for example, brings workers to rural farms24, 25 and the Wisconsin Department of Administration’s (WI DOA’s) state vanpool brings state and non-state employees from distance areas to jobs in Madison, WI26.

Implementation Resources

NCTR-Ridematching - National Center for Transit Research (NCTR). Ridematching software: list of programs with ridematching systems. Center for Urban Transportation Research (CUTR), University of South Florida (USF).

Gishigo - GishiGo. Ride share network.


* Journal subscription may be required for access.

1 UC Davis-Yura 2006 - Yura EA, Eisinger D, Deb Niemeier. A review of on-road vehicle mitigation measures. Davis: University of California, Davis; 2006.

2 ICF Consulting 2006 - ICF Consulting. Bay Area Air Quality Management District performance review of selected TFCA project types: Final report. Fairfax: ICF Consulting; 2006.

3 RAND-Sorenson 2008 - Sorenson P, Wachs M, Min EY, et al. Moving Los Angeles: Short-term policy options for improving transportation. Santa Monica: RAND Corporation; 2008: Monograph Report 748.

4 Gallivan 2011 - Gallivan F, Ang-Olson J, Liban CB, Kusumoto A. Cost-effective approaches to reduce greenhouse gas emissions through public transportation in Los Angeles, California. Transportation Research Record: Journal of the Transportation Research Board. 2011;2(2217):19-29.

5 Silva-Send 2013 - Silva-Send N, Anders S, Narwold A. Cost effectiveness comparison of certain transportation measures to mitigate greenhouse gas emissions in San Diego County, California. Energy Policy. 2013;62:1428–33.

6 Silvis 2009 - Silvis J, Niemeier D. Social network and dwelling characteristics that influence ridesharing behavior of seniors. Transportation Research Record: Journal of the Transportation Research Board. 2009;(2118):47-54.

7 Robbins 2015 - Robbins WA, Berman BA, Stone DS. Health effects of vanpooling to work. Workplace Health & Safety. 2015;63(12):554-563.

8 Graham-Rowe 2011 - Graham-Rowe E, Skippon S, Gardner B, Abraham C. Can we reduce car use and, if so, how? A review of available evidence. Transportation Research Part A: Policy and Practice. 2011;45(5):401–18.

9 Chaube 2010 - Chaube V, Kavanaugh AL, Pérez-Quiñones MA. Leveraging social networks to embed trust in rideshare programs. In: Proceedings of the 43rd Hawaii International Conference on System Sciences - 2010. Washington, DC: Institute of Electrical and Electronics Engineers (IEEE); 2010.

10 Deakin 2010 - Deakin E, Frick KT, Shively KM. Markets for dynamic ridesharing? Case of Berkeley, California. Transportation Research Record: Journal of the Transportation Research Board. 2010;2187:131-7.

11 Levofsky 2001 - Levofsky A, Greenberg A. Organized dynamic ride sharing: The potential environmental benefits and the opportunity for advancing the concept. Washington, DC: Transportation Research Board 2001 Annual Meeting. 2001: Working Paper 01-0577.

12 Erdogan 2015 - Erdogan S, Cirillo C, Tremblay JM. Ridesharing as a green commute alternative: A campus case study. International Journal of Sustainable Transportation. 2015;9(5):377-388.

13 Li 2007 - Li J, Embry P, Mattingly SP, et al. Who chooses to carpool and why? Examination of Texas carpoolers. Transportation Research Record: Journal of the Transportation Research Board. 2007;2021:110-7.

14 Salon 2012 - Salon D, Boarnet MG, Handy S, Spears S, Tal G. How do local actions affect VMT? A critical review of the empirical evidence. Transportation Research Part D: Transport and Environment. 2012;17(7):495-508.

15 Willson 2008 - Willson RW, Brown KD. Carbon neutrality at the local level: Achievable goal or fantasy? Journal of the American Planning Association. 2008;74(4):497-504.

16 Javid 2016 - Javid RJ, Nejat A, Salari M. The environmental impacts of carpooling in the United States. 2016.

17 Shewmake 2012 - Shewmake S. Can carpooling clear the road and clean the air?: Evidence from the literature on the impact of HOV lanes on VMT and air pollution. Journal of Planning Literature. 2012;27(4):363–74.

18 Chan 2012 - Chan ND, Shaheen SA. Ridesharing in North America: Past, present, and future. Transport Reviews: A Transnational Transdisciplinary Journal. 2012;32(1):93-112.

19 eRideShare -

20 Ridester - Ridester. Life is journey. Share it.

21 Drive Less Connect - Drive Less, Connect. Matching people with places: Oregon’s secure, online ride-matching tool.

22 MDOT-Rideshare - Michigan Department of Transportation (MDOT). Michigan Rideshare: Share the ride, share the cost.

23 WSDOT-Carpool - Washington State Department of Transportation (WSDOT). Carpools & vanpools.

24 Sampson 2014 - Sampson R. CalVans: An easy ride to the hard work on a farm. California Vanpool Authority. 2014.

25 CalVans - California Vanpool Authority (CalVans). California’s single source for ridesharing to work or college in a CalVans vehicle.

26 WI DOA-Vanpool - Wisconsin Department of Administration (WI DOA). Joining a vanpool.

Date Last Updated