Visiting ISM at Cologne Messe, then Toy Fair at Nuremberg.

Leaving the Cologne show at say 4pm, and will be staying in a hotel in Forchheim which I understand is about 40k north of Nuremberg.

Train time is +/- 4 hours, but involves going to Nuremberg and then coming back again, and is not frequent (and no miles ). Flight sounds like hard work, so I'm thinking about hiring a car and driving. How busy is that route likely to be ?

Any suggestions welcome.
ta