Motor companies, some universities and institutes have their own tracks.
They looks like racing track but aren’t intended for racing.
Can I tag them “highway=raceway”?
It looks like you answered that question with your statement above it. If it isn’t a raceway, you shouldn’t tag it as a raceway.
I haven’t had to map one of these myself, but I think I would use highway=service + access=private. I can’t think of a more specific tag off the top of my head.
A few examples:
- Gaydon in Warwickshire (Jaguar-Land Rover) https://www.openstreetmap.org/way/55116309
- Merida Police Academy : https://www.openstreetmap.org/way/38288436#map=16/38.9177/-6.3684
- Fire Service College, Moreton-in-Marsh, has a section of ‘motorway’ : https://www.openstreetmap.org/way/401207894
- VW Wolfsburg : https://www.openstreetmap.org/relation/62771#map=16/52.4456/10.7471