Rother Valley bear

Driving from Beighton to Killamarsh (the back road to Rother Valley) last night when I have seen what looked like a black bear at the side of the road.

As I've drove past I've thought what's that? Looked closer and thought, oh it's a bear, a split second later when it's dawned on me what I thought I'd seen I'm then thinking IT'S A BEAR??? Next moment I'm then telling myself it's got to be a big dog and was looking out of my rear-view and wing mirrors for a person walking their dog, except I couldn't really see anyone.

It was dark, the bear/dog was on the other side of the road next to some shrubbery and I only got a fleeting glance really but it did seem very thick-set at the top end of it's body like what you would expect of a bear.

I'm guessing it must have been a big black dog but has anyone else had any similar sightings in that area recently?