Citizens for Appropriate Transportation (CAT) Issue Brief

Eisenhower Transportation Corridor

HOV / HOT LANES – A PRIMER

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What are HOV / HOT lanes?  A High-Occupancy Vehicle Lane is a car pool lane.  A High-Occupancy Toll Lane is a car pool lane that charges tolls.  For the Eisenhower Corridor, the Illinois Department of Transportation (IDOT) is considering Build Alternatives that would add one lane each way from Austin Boulevard to Mannheim Road.  The extra lane each way could be general purpose, HOV, or HOT. 

Are there HOV / HOT lanes elsewhere?  There are HOV or HOT lanes in several metropolitan areas, including Atlanta, Dallas, Houston, Los Angeles, Miami, Minneapolis – St. Paul, San Francisco, Seattle, and Washington D.C.

What is the theory behind HOV / HOT lanes?  With more people in each vehicle, there are fewer vehicles needed to reach the same capacity.  If each vehicle in an HOV lane carries three people, then the lane can have one-third as much traffic as a general traffic lane and still have the same people-carrying capacity.  With fewer vehicles in the HOV lane, users will have a shorter travel time.

What are HOV / HOT lanes supposed to do?  HOV / HOT lanes can decrease travel time, increase the vehicle and person capacity of a roadway, and decrease air pollution.

What are the differences among HOV /HOT projects?  Some differences among HOV / HOT projects are:  (1) all vehicles or buses-only, (2) full-time or part-time (peak hours only), (3) painted stripes or barrier separation from general traffic lanes, (4) variable or fixed rate tolls, and (5) pricing policies.

Have any HOV lanes been discontinued?  Yes. Both New Jersey and New York have either discontinued or canceled HOV projects. 

Don't HOV / HOT lanes require careful management?  Yes they do. HOV / HOT lanes do not work with either too much traffic or too little traffic.  Too much traffic means longer trip times so users do not get reduced travel times.  Too little traffic creates the "empty lane syndrome" where the capacity of the HOV lane is underutilized and more congestion and longer travel times occur on the general traffic lanes.

Are car pools hard to form?  People who work late or irregular hours, use their cars during the day, park free at work, have young children or aging parents, and who need to run errands during their commute are less inclined to car pool.

Is there an unbiased study on HOV lanes?  A report by the nonpartisan Legislative Analyst’s Office in California said, "Based on our review of available data, we conclude that the performance of HOV lanes is mixed." (HOV Lanes in California: Are They Achieving Their Goals?)  The report continues: HOV lanes in California operate at only two-thirds of their capacity, the impact of HOV lanes on air quality is unknown because documentation is based on models and projections rather than actual emission data, and HOV lane use does not necessarily increase over time, contradicting the theory that people form car pools to take advantage of them.

CONCLUSION:  If the purpose of the proposed Ike expansion is to increase roadway and person capacity, then IDOT must prove that HOV or HOT lanes are better than other alternatives. 

Rick Kuner – revised May 2015