Adjective
Suitable for riding; as, a ridable horse; a ridable road.
Source: Webster's dictionaryThe size of engines depends on the scale and can vary from convert tall for the largest ridable live steam scales such as 1:4, down to matchbox size for the smallest: Z-scale (1:220) or T scale (1:450). Source: Internet
The articulate, sentient pet he inherited from his late father has gradually grown from the size of a collie pup to a ridable behemoth—especially after consuming a used car. Source: Internet