Two elderly couples share a car

They're driving on the German motorway. Their speed is exactly 81 km/h. A police officer stops them. One of the elderly chaps asks:

'Good day officer, were we speeding?'

'No, not at all. But why are you going so slowly?'

'Why, can we drive faster?'

'Of course, 130km/h easily.'

'But on the signpost it says A81.'

'Yes, so?'

'Well, we thought that 81 km/h was the limit then.'

'Oh no, that's just the motorway's number.'

'Oh, ok. Thanks for the information!'

Before letting them go, the policeman looks into the car, the back seat specifically, where he sees two petrified old women. So he asks:

'What's the matter with the two ladies in the backseat? Do they feel alright?'

'Oh yes, most certainly. It's just that we left the B252 two minutes ago.'