blocked section; impassable spot
Used for sections of roads, railways, or communication lines that are blocked or out of service, often due to disaster or construction.
Heavy rain caused several blocked sections.
Restoration of the impassable spots is expected to take time.
不通 means 'suspended' or 'out of service' and is used for entire lines or services, while 不通箇所 refers to the specific physical location of the blockage.
通行止め is a general term for 'road closed', often used on signs, while 不通箇所 is more technical and used in reports or news about specific impassable points.
Compound of 不通 (suspension, interruption) and 箇所 (place, spot). The exact historical derivation is uncertain, but the word is a straightforward modern technical compound.