Greyhound therapy is a pejorative term used in the USA health care system since the mid-1960s in reference to the practice by mental-health authorities of buying a ticket on a Greyhound Lines bus interstate to get rid of possible "troublemaker" patients.
The practice is still in use in certain mental-health circles.
Diesel therapy (a.k.a. motorcoach therapy) is a similar term for the practice, and is usually used pejoratively.
References
Greyhound therapy Wikipedia(Text) CC BY-SA