Each load-carrier of a system is always controlled by one of a series of MCUs (monitoring and control units) that are assigned to contiguous regions along guideways. Each carrier is slowed down to maintain a safe distance behind a carrier ahead, or to avoid collision with another carrier when approaching a merge point of a convergent Y-junction or when otherwise desirable. Distance measurements take into account the lengths of carriers and of assigned regions and the counts of speed pulses sent to MCUs since entry of carriers into their respective regions. For merge control, arrival data are developed that include the times and speeds to and at arrival of two carriers at a merge point. Through repeated comparisons of arrival data developed from one carrier with arrival data previously developed and stored as to the other carrier, the one carrier is gradually slowed down as necessary to avoid a collision.