Traffic congestion: a situation where vehicles or people crowd a road or transport network, slowing the flow (often used as 渋滞する).
連休で高速道路が渋滞している。
The highway is congested because of the long holiday.
朝の通勤時間は駅前が渋滞する。
The area in front of the station gets congested during the morning commute.
事故のために市街地で大渋滞が起きた。
A major traffic jam occurred in the city because of an accident.
イベント会場の周りは渋滞で進まない。
Traffic around the event venue isn't moving due to congestion.
Delay or stagnation: the slowing or halting of progress or flow (e.g., delays in schedules or stagnation in systems/economy).
書類の確認不足でプロジェクトに渋滞が生じた。
Lack of document checks caused delays in the project.
物流の渋滞で商品の到着が遅れている。
Shipments are delayed due to congestion in logistics.
手続きの渋滞が解消されるまで時間がかかるだろう。
It will take time until the procedural backlog is cleared.