Vandals forced the closure of the M27 when they left drivers in danger of electrocution.
Police shut the motorway amid fears 33,000-volt cables could crash to the ground following a fire in a wooden pole carrying the lines across the road close to Fareham.
Queues up to eight miles long built up in both directions on the motorway.
Traffic on the A27 in and out of Portsmouth also ground to a halt as police set up diversions at 9.20am.
Southern Electric operation and maintenance engineer Malcolm Goddard condemned the vandals for not only causing tremendous inconvenience to motorists, but also putting their own lives at risk.
He said: ‘It appears they threw some wire on to the overhead cable. This caused a fault and the pole caught fire.
‘These vandals, not only caused major disruption to road users, but subjected themselves to serious danger.
‘It was an absolutely foolish thing to do. They could have been injured themselves when throwing the wire. It was totally reckless.’