In the past decade, a variety of questions have been raised concerning the effectiveness of high-occupancy vehicle (HOV) lanes. In Southern California, recent evaluation studies on HOV lanes confirm the effectiveness of HOV lanes in several ways. However, little research has been performed to evaluate the air quality benefits of HOV lanes. This paper describes a study that examines operational differences in traffic dynamics between HOV lanes and mixed-flow (MF) lanes and evaluates their impacts on vehicle emissions. Four general HOV lane scenarios were identified: underutilized, neutral, well utilized, and overutilized. Extensive driving trajectories in both lane types for each scenario were collected. Their speed profile and joint speed-acceleration frequency distribution were analyzed and compared. Vehicle emissions and fuel consumption were then estimated with a state-of-the-art modal emissions model. The results show that HOV lanes produce lower emission rates per vehicle per mile in most cases, except when they are underutilized. When normalized by average vehicle occupancy, HOV lanes produce much lower emission rates per the same amount of travel demand, on the order of 10% to 70%. In almost every case, HOV lanes produce less emissions mass on a per-lane basis than MF lanes. Southern California freeway lane performance matrices show that on a typical weekday during the summer of 2005, HOV lanes operated mostly under Scenarios 1 and 2 during peak periods. Overall, they were well utilized about 14% to 17% of the time. According to the emissions estimates, the HOV lanes are considered effective in reducing vehicle emissions.

In the past decade, a variety of questions have been raised concerning the effectiveness of high-occupancy vehicle (HOV) lanes. In Southern California, recent evaluation studies on HOV lanes confirm the effectiveness of HOV lanes in several ways. However, little research has been performed to evaluate the air quality benefits of HOV lanes. This paper describes a study that examines operational differences in traffic dynamics between HOV lanes and mixed-flow (MF) lanes and evaluates their impacts on vehicle emissions. Four general HOV lane scenarios were identified: underutilized, neutral, well utilized, and overutilized. Extensive driving trajectories in both lane types for each scenario were collected. Their speed profile and joint speed–acceleration frequency distribution were analyzed and compared. Vehicle emissions and fuel consumption were then estimated with a state-of-the-art modal emissions model. The results show that HOV lanes produce lower emission rates per vehicle per mile in most cases, except when they are underutilized. When normalized by average vehicle occupancy, HOV lanes produce much lower emission rates per the same amount of travel demand, on the order of 10% to 70%. In almost every case, HOV lanes produce less emissions mass on a per-lane basis than MF lanes. Southern California freeway lane performance matrices show that on a typical weekday during the summer of 2005, HOV lanes operated mostly under Scenarios 1 and 2 during peak periods. Overall, they were well utilized about 14% to 17% of the time. According to the emissions estimates, the HOV lanes are considered effective in reducing vehicle emissions.

Every agency responsible for the maintenance of roadway systems faces the problem of insufficient funding to perform all of the necessary repairs on pavement sections. Therefore, highway agencies must adopt a pavement management system (PMS) to help set priorities. The PMS includes a method for evaluating pavement performance on a routine basis and identifying sections with a need for rehabilitation or maintenance. Some states in the U.S. use a pavement rating system that is based solely on visible surface distresses, while others use an index based on ride quality alone to perform the regular evaluation of pavements and to select projects. Increasingly, many states are using a combination of distress and ride quality. The Ohio Department of Transportation (ODOT) utilizes the Pavement Condition Rating (PCR), based on surface distress, for project selection. This paper outlines the development of a new performance index for pavements that incorporates aspects of ride quality together with surface distress for possible adoption by ODOT. The proposed index is called the Pavement Quality Index (PQI). The PQI does not require any new measurements or methods; rather, it simply utilizes procedures that are already in place and well established in Ohio. The PQI is an amalgam of the PCR and the International Roughness Index (IRI). The development of the new index is the natural extension of the growing trend that transportation agencies are placing increased emphasis on customer satisfaction, and also introducing performance-based specifications.