The whole plan was built, according to the movie, around dropping parachute troops at key bridges and then having ground troops charge along a single road. The soldiers on the ground had 48 hours to get to the last of the airborne soldiers, who were at Arnhem. They didn't make it, hence the idea that the plan always involved going one bridge too far.
There are wrecks everywhere and the dead are everywhere after the first clash in the campaign. As soldiers clear the way and take away the wounded, one officer looks up at another who is sitting on a scout car. How do the generals expect them to keep up the pace under these conditions, the fellow asks looking up. The fellow sitting on the armoured car has his binoculars and is scanning the road ahead. J.O.E Vandeleur, played by Michael Caine, looks down at his cousin, Giles, and says:
"You don't know the worst. This bit we're on now?"
"Yes," says Giles, quizzically.
"It's the wide part."