When making a lane change in a tractor-trailer, how should you check for vehicles in the blind spot?

Combination vehicles have very large blind spots, especially along the right side of the trailer and immediately behind it. Before any lane change: signal early; check both flat (West Coast) and convex (spot) mirrors; if your seating allows it, glance over your shoulder for vehicles in adjacent lanes; and execute the lane change gradually. The flat mirror shows objects at their true size and distance; the convex makes them appear smaller and farther away, so do not judge gaps from convex mirror alone. Signal alone is not a substitute for checking — drivers in your blind spot did not see your turn signal, and assuming the lane is clear because no one honked is not a safe technique.