A Taser gun has been used to help capture a stray Rottweiler that attacked two motorists after sedatives failed to subdue the dog.
The incident led to the closure of the A47 between Guyhirn and Wisbech, Cambs, for five hours on Wednesday.
After consulting a vet, the police used sedatives in food to try to calm the animal but despite eating two portions, the Rottweiler could not be subdued.
Eventually the police used Taser guns and the dog is being held in a kennel.
"The road was closed for five hours and, as a last resort, we tasered the dog to capture it. It was then taken to a vet," said police.
The road was reopened at 1700 GMT.
"Seven tablets (containing sedatives) were mixed with food and a police dog handler got as close to the dog as the animal would allow and left the food," said a police spokeswoman.
"The dog ate it but the sedative did not take effect so the remaining seven tablets were used in the same way.
"As a final resort the dog was tasered, before being loaded into a van and taken to a vet to be looked over. The animal is in good health."
Officers are still trying to trace the owner of the dog.