The first med school which interviewed DD sent out a dress code relevant to hospital wear but we took it as a heavy hint about what to wear for interview.
This is mainly relevant to women but it was - no jewellery other than a watch and ear studs, hair off face and secure with a discreet fastening, flat or low-heeled shoes with closed toes and a secure heel (ie, no sling-backs), skirt not too long/not too short, minimal make-up, no bare legs, no wide trousers. All sensible really.
She tells me that all men wore suits and ties or jackets and ties with dark trousers. Women wore dresses or smart skirt ensembles.
They all involved a trudge from the station and, often, a guided tour so definitely wear something comfortable on feet.
The most distant one meant she had a lot of stuff to carry but she was fortunate in that a friend of mine has an office not far from her route so she was able to freshen up there and dump excess stuff to be retrieved later. For that one she changed from flats to a low heel a) because she could without having to lug an extra pair round, and b) a slight heel made her feel better/more confident.
She was surprised how many candidates had parents in tow. It never crossed my mind to go with her!