After East and West Germany signed a Transit agreement in 1971, people trying to escape across the Berlin Wall were less likely to use subterranean tunnels than to conceal themselves in food trucks or rental vans as they passed through checkpoints. Some were helped by friends or family but more turned to professionals, who charged as much as 45,000 marks for their expertise in smuggling people over the border. The East German authorities searched vehicles for stowaways and handed out stiff prison sentences to Fluchthelfer, who were vilified as criminal traffickers.