Slugging in Houston: Casual Carpool Passenger Characteristics

In the last thirty years, determined travelers have developed a new method of travel that offers the benefits of traveling on an HOV lane without forming traditional carpools. Casual carpools (also known as “slugging”) are impromptu carpools formed among strangers in order to meet the occupancy requirements of HOV lanes. In this research, survey respondent data from Houston, Texas were used to evaluate the behavior of casual carpool passengers. At the time of this research, there were approximately 500 daily casual carpool passengers in Houston during the morning peak period. These passengers saved up to 13 minutes of travel time compared to the alternative of driving alone on the main lanes. Statistical models were used to evaluate the socio-economic and commute characteristics that would indicate an increased likelihood of a traveler choosing to casual carpool. The results of the analyses indicated that being on a commute trip, making more trips per week, being between the ages of 25 and 34, and having occupations that were either professional/managerial or administrative/clerical all increased the likelihood of a traveler choosing to casual carpool. Additionally, having a household income between $25,000 and $35,000 significantly reduced the likelihood of casual carpooling. The research results provided insight into some of the factors that influenced traveler’s decision to casual carpool. It is important to understand the types of travelers that casual carpooled, and the information learned in these analyses can be used to better evaluate HOV and HOT lane use and performance. Casual carpool passengers can comprise a significant portion of HOV/HOT lane person movement and should be considered when investigating HOV or HOT lane implementation.