Before changing lanes, a driver must:Check rear view and side mirrors for any vehicles behind or beside.Look over your shoulder to check the blind spot.Turn on the appropriate signal light at least 3 seconds before moving.Ensure the lane is clear and safe before making the maneuver.Change lanes smoothly without sudden movements.Changing lanes without signaling or without checking blind spots can cause accidents and lead to traffic violations. Always practice courtesy and caution when changing lanes.