Hitchhiking

Nature

Hitchhiking (also known as thumbing, autostop or hitching) is a means of transportation that is gained by asking individuals, usually strangers, for a ride in their car or other vehicle. The ride is usually, but not always, free.

Nomads have also used hitchhiking as a primary mode of travel for the better part of the last century, and continue to do so today.

Source: Wikipedia

Incidence 
In some countries there is a rising rate of crime associated with hitchhiking. A growing number of hitch-hikers are being killed and a large number of motorists who have picked up hitchhikers have been robbed, beaten or killed.
Broader 
Type 
(E) Emanations of other problems