This issue contains 19 papers on the subject of traffic flow theory and characteristics. Specific topics discussed include the following: freeway merging and diverging effects on traffic oscillations; mesoscopic modeling of bus transit operations; modeling the effect of weather on traffic flow breakdown; multiclass kinematic wave model; car-following models; multistate model of travel time reliability; macroscopic characteristics of lane-changing traffic; intradriver heterogeneity in car-following; onset of congestion from low-speed merging maneuvers; merging behavior at freeway on-ramps; multiclass traffic flow model; cellular automata model for work zone traffic; modeling vehicular merging behavior; site-specific stochastic freeway breakdown and queue discharge; effect of light from vehicle windows on traffic flow; traffic density estimation along signalized arterials; and causal factors that play a role in car-following behavior.