Sentence:  Proponents of the system pronounced it a success, especially among the student youth. "The working class earns money and it can travel on buses or trains or airplanes, but students are the most happy, energetic people, and <WSD>autostop</WSD> is convenient for them," insisted one supporter in 1966. 
Meaning of the word marked with <WSD> tags:  A coupon-based system of hitchhiking.