Texas A&M study Reveals Impact of HOT lanes on Carpooling

A research study performed by Texas A&M University, Dept of Civil Engineering:

Burris, M., Alemazkoor, N.*, Benz, R., Wood, N. (2014)
The Impact of HOT Lanes on Carpools.” Research in Transportation Economics, Vol. 44. DOI: 10.1016/j.retrec.2014.04.004. pp. 43 – 51.

In that study, researchers concluded “…it does appear that carpooling is often negatively impacted by converting a HOV lane to a HOT lane.”

This is corroborated by numerous comments posted on this website, on our facebook community and group, and as people sign the petition, which state that they have quit bothering to carpool because it doesn’t save them anything.  We’re still waiting to hear someone say that they started carpooling as a result of the toll.

In addition, WSDOT reported in comments on their blog the following HOV usage vs. SOV on I-405 Express Toll Lanes (ETL):

For peak periods on weekdays for 11/30/15 – 12/4/15,

For southbound trips on I-405 during the 5–9 a.m. peak period, there were approximately 15 percent declared as HOV.
For northbound trips on I-405 during the 3–7 p.m. peak period, there were approximately 16 percent declared as HOV.

Over a full day in November (not just peak periods), about 75 percent of all users during weekdays and about half of all weekend trips are paying tolls.

Let’s focus for a moment on I-405 north of SR522 where there is one ETL and 2 GPLs.  Visual observations made by stop405tolls.org team during peak hours in late December and early January generally confirmed these figures.

In other words, prior to the 405ETL, 100% of the vehicles in the carpool lane were HOVs.
Since the 405ETL was implemented only 15% of the vehicles in the carpool lane are HOVs.
That is a 58% reduction in the capacity of PEOPLE in the Express Toll Lane.  This is a direct result of displacing 2 person carpools from the ETL.  Statistics, particularly using percentages, make for great manipulation of the facts.  What would be most helpful here is to have the actual numbers of vehicles — HOVs, SOVs, motorcycles, and buses — in both the ETLs and the GPLs.  But what is certain is that the ETL north of 195th is emptier than it was when it was not tolled and filled with carpools.


The following study was taken from


Some important facts:
– This study included SR167. That road allowed carpools WITHOUT requiring a transponder
SR167 has a surplus of capacity in the carpool lane allowing for selling the extra capacity to Single Occupancy Vehicles (SOVs).
– There may be a correlation between HOV ridership and gas prices.
– HOV ridership is lower on SR167 than on other highways in the area.

This study found carpool participation declined when lanes were opened up to SOVs, especially when HOVs were also charged a toll.  Generally confirming the attitude “why bother to carpool when I can just pay”.


Posted in Uncategorized
3 comments on “Texas A&M study Reveals Impact of HOT lanes on Carpooling
  1. […] system is less effective than a 2+ carpool system.  Charging a toll does not increase capacity; it decreases participation in carpooling as proven by research at Texas A&M University Dept of Civil Engineering; and it is a terribly […]


  2. […] of the HOV lane and replaced with those who can – and will – pay.  I reported on the  Texas A&M University research that proved carpools would decline with HOT lanes.  Their research even included SR167.  I also […]


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