A major road near Halifax was closed after large boulders fell from a rock face.
The uphill section of the A629 Elland by-pass was earlier closed between the Elland turn-off and the M62 "in the interests of public safety".
Calderdale council said a rock trap had been constructed in the road to trap any more falling rocks.
A footpath at the road side has been diverted away from the rock face, which is the remnant of an abandoned quarry.
A Calderdale Council spokesman said: "It's a rock face which is exposed and eroding with some very big boulders and loose shale in there.
"There's nothing much we can do with that area over and above a process of containment in case any more rocks come down in future."
The council said the road was due to reopen at 1600 BST.