A rest area (or service area (RSA), service station) is a public facility located next to a motorway at which drivers and passengers can rest, eat, or refuel without exiting on to secondary roads. It can be a great place for hitchhiking: you can ask for a ride when drivers re-fill or wander around the area, or you can stand by its exit (that leads to a motorway) and hitchhike there.
Facilities of the rest area may include park-like areas, fuel stations, toilets, and restaurants. Rest areas are common in the United States, Canada, Australia and parts of Europe (France: Aire de service, Germany: Raststätte (directly on the Autobahn) and Autohof (somewhat off the Autobahn), Italy: Area Servizio, United Kingdom: Motorway services, Austria: Autobahnstation, Denmark: Serviceanlæg, Info-teria, Hungary: Pihenohely, Netherlands: verzorgingsplaats, Slovenia: Počivališča) and Asia.
Not all rest areas include petrol stations - this means that the traffic on such rest areas will, in general, be much lower, and one can expect more difficulties when looking for a ride there. For service areas with gas stations see information here.
Get out of a rest area
It might be necessary to get out of a rest station because it's empty and you think it will be easier to try to hitch on the local roads, because you are really close to your destination, you are on the wrong side of the motorway or you want to camp (see below). Many rest areas are fenced but it is usually possible to get out even in those cases. Many times there are breaks in the fence, you can also try to see if there is a possibility to get out from the entrance or the exit, and of course see if it's possible to jump over the fence. You can even ask to the people of the station to open you the door, keeping in mind that in this case you will not be able to re-enter the station.
It is possible to sleep at rest areas, but you are advised to keep a low profile, as it may not always be legal to do so. Be aware that those areas that lend themselves to sleeping are usually also used as public toilets, so a flashlight is an absolute necessity when it's dark.
Also, be aware that rest areas may not be the safest places due to petty crime.
Kimdime managed to camp in rest areas where there was trees and/or places reasonably hidden.
Prino has slept on many rest areas in many countries of Europe. The key is to disappear when nobody is watching and to avoid the aforementioned "public toilet areas". On one occasion he even managed to sleep right in the middle of a small bed of shrubs on an Italian area Servizio, reasoning that nobody would actually expect anyone to be so bold. However, in general he prefers to sleep in the restaurant, finding either a closed-off section, or a far-away corner. It is both safer and warmer.
Hippietrail has slept right on the benches at the front of several rest areas in Japan with no problems at all.
In most states of the United States there are no petrol stations on rest areas. In these states the rest areas are a relatively good option for hitchhiking. In some of them (Ohio?) you will even find free wireless internet. In New Hampshire you can try to hitchhike at the state liquor stores that are very popular because of the state's low (non-existing?) tax on alcohol.