Clearly you need the right incentives for drivers. Poland had a neat system for hitchhikers back in the day. A hitchhiker bought a book of tickets. It included

Clearly you need the right incentives for drivers. Poland had a neat system for hitchhikers back in the day. A hitchhiker bought a book of tickets. It included a small, distinct sign to hold up to signal drivers. When you got a ride, you tore off a coupon the driver, and each ticket was ... (drum roll please...) a lottery ticket. So, every lift you gave gave you the driver a non-zero shot at a prize.