The M5 was closed in both directions last night following a very serious incident involving three cars and a lorry.
The southbound carriageway reopened on Wednesday evening; the northbound road is expected to be clear in the early hours of Thursday.
It follows another collision earlier in the afternoon in which a casualty was taken to hospital in a critical condition by air ambulance.
The build up led to problems on diversion routes including the A396 from Tiverton to Exeter, the B3181 from Cullompton to Exeter and numerous local roads.
The Sowton, Pinhoe, Heavitree and Sandygate areas in Exeter were particularly badly affected.
Other local roads in Exeter, Honiton, Cullompton and Tiverton were at a standstill for much of the evening.
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