The difference between Lay-by and Rest stop

Lay-by as a noun (UK):

A paved area at the side of a highway designated for drivers to stop in, for emergency parking, or where vehicles can wait, with larger lay-bys possibly having facilities like food vendors or public telephones.

Lay-by as a noun (UK):

A railroad siding; a second, short railroad track just to the side of a railroad track, connected with the main track by a switch and used for unloading, bypassing, etc.

Lay-by as a noun (nautical):

A widened section of a narrow river or canal, formed to one side so as to leave the channel free, for mooring of vessels, where vessels can lay over or allow others to pass.

Lay-by as a noun (Australia, New Zealand, South Africa):

A method of retail purchase in which the selected goods are set aside and the customer pays for them in instalments, receiving them when fully paid; layaway.

Rest stop as a noun:

A rest area.