THE northbound carriageway of the M5 was closed after a pile-up involving 15 cars between Taunton and Wellington on Thursday.
Three people were taken to Musgrove Park Hospital with minor injuries.
Police blamed poor weather for the accident, and reminded motorists to adjust their driving and speed in wet weather.
Traffic was diverted off the motorway on to surrounding roads, causing severe delays in Taunton.
Eyewitness Alison Hulls said: "I was driving in the middle lane in heavy rain and had just noticed a very low-flying helicopter to my left when cars to my right collided in the overtaking lane, and the car in front of me hit something in front of him.
"I thought I had no chance to miss him, and I could hear vehicles crashing behind me, but I swung left and somehow -- I still don't know how --managed to squeeze past and on to the hard shoulder.
"I sat shaking while I called the emergency services. I feel incredibly lucky to have come out of it unscathed. It was every motorway driver's worst nightmare and it happened so fast."
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