High occupancy vehicle (HOV) lanes are freeway lanes reserved for vehicles with more than a predetermined number of occupants. HOV lanes can affect the capacity of a freeway through both an underutilization effect and a disruption effect caused by lane-changes. This book examines the physics of HOV lanes and their overall impact on traffic. It uses a simple car-following model with lane-changing that matches field data with considerable accuracy. Current models of this type have usually a large number of parameters, many of them unobservable and/or with no physical meaning. This one, in...