If the park is in my neck of the woods, I can just use this definition:

"vehicle" means a device in, on or by which a person or thing is or may be transported or drawn on a highway, but does not include a device designed to be moved by human power, a device used exclusively on stationary rails or tracks, mobile equipment, a motor assisted cycle or a regulated motorized personal mobility device

[BC Motor Vehicle Act, 1 Definitions]

https://www.bclaws.gov.bc.ca/civix/document/id/complete/stat...

The words written on some sign on a road or park are not meant to be freely defined by whoever happens to be reading the sign.