A dog was rushed to the vets in the back of a police car after being knocked down on the A41.
Officers came to the aid of the pooch just after 8pm on Sunday night.
Many passing motorists had also stopped to help the pet.
The accident happened close to the Bourne End junction and the dog is thought to have suffered broken back legs.
Officers took the dog to Barton Lodge Vets in Midland Road, Hemel Hempstead.
The pet, thought to be an Italian Spinone, has since been transferred to its regular veterinary clinic for treatment.