Higher barriers cannot be put on Scammonden Bridge after a spate of suicides at the M62 landmark.
Highways England reviewed safety on the bridge after a series of tragic incidents.
But they say higher railings would put extra weight pressure on the bridge deck which may weaken it.
Wind is also a factor, according to the latest safety review seen by the Examiner.
In 2015 Highways England looked at a ‘suicide prevention parapet’ over the bridge which would make it harder for people to reach the edge of the bridge, sometimes referred to as Rainbow Bridge.
At the time there had been 10 incidents between 2008 and 2015, with one fatality and nine people talked down.
A man was killed when he fell from the bridge just before 7am on Bank Holiday Monday August 28.
The survey says the existing height of the railings is 1.25m.
It acknowledges it may have “sufficient strength” to carry a 1.8m height parapet, under vehicle impact and vertical loads only, but excluding the wind effects.
But it is the wind load on a proposed 1.8m height parapet which may cause failure of the supporting piers to the bridge deck.
As a result, Highways England say the existing parapet anchors are not capable of taking a 1.8m height parapet.
A spokesperson for Highways England said: “We have committed to reducing suicides on our network and we have been working with a number of organisations and charities who are experts in this field and our Suicide Prevention strategy will be published later this year.
“We regularly review the structure of Scammonden bridge. However, increasing the height of the bridge barrier is not possible due to the extra weight this would put on the bridge itself.
“Following incidents we always work closely with the police and other services to see if any lessons can be learned.”
Removing pedestrian access was once looked at, but they felt it would not be approved at planning level.
The highways body continue to work with the Samaritans who installed signs on the bridge in 2008.
In 2015 former Colne Valley MP Jason McCartney raised concerns on behalf of a constituent.
He was told a repair scheme was planned for 2018/19 but the existing parapet would be replaced on a like for like basis.
Highways England did tell him, however, they would revisit the design for the parapet before work was done to establish if enhancements can be made.