"Friedkin was certainly ambitious in how he shot the film. The most famous scene takes place on a rickety rope bridge as the trucks attempt to traverse it. In his memoir, the director explains that the entire sequence took over three months to shoot and construction of the bridge cost $1 million.
"When the original river meant for the scene went dry, the crew was forced to tear down and rebuild the bridge elsewhere at the cost of another million dollars. When the second river proved just as difficult, Friedkin and the crew were forced to add an artificial current and rainstorm. He says that it was the single most difficult sequence he ever filmed in his career."