The FIA groups cars into categories to ensure cars are on track with their equals and the track is suitable for the group. Dimensions and safety features amongst others. 

The FIA classify Formula 1 as Group D with cars having a weight/power ratio of less than 1kg/hp and requires them to run on a Grade 1 track.

Also Group E (Free Formula) and historic cars including post-1985 F1 cars.

Andrew Burden

The author Kiwi F1 Fan