The convoy effect in process scheduling As I understand the convoy effect, in the context of vehicular traffic in a road system. A slow moving group of vehicles passes through the system, slowing traffic even in areas which were not directly affected by the convoy.

How does this apply in the context of CPU scheduling? It does not seem to be an analogous situation.
FCFS (First-Come, First-Served) scheduling can also cause blocking in a busy dynamic system in another way, known as the convoy effect. 

When one CPU intensive process blocks the CPU, a number of I/O intensive processes can get backed up behind it, leaving the I/O devices idle. When the CPU hog finally relinquishes the CPU, then the I/O processes pass through the CPU quickly, leaving the CPU idle while everyone queues up for I/O, and then the cycle repeats itself when the CPU intensive process gets back to the ready queue.