A 25-year-old woman was killed when her car span out of control on a wet road where drains had not been cleared for three years.
Chloe Wright's car aquaplaned and spun 90 degrees before crashing into an oncoming van. She died instantly.
An inquest into her death found that the blocked drains may have caused her to crash.
Police investigating the incident on the A281 in Mannings Heath, near Horsham, said water was running across the road and during heavy rain it stood at 2mm deep.
The hearing at Haywards Heath Town Hall was told that at least two of the three drains, managed by West Sussex County Council, were totally blocked with silt and detritus and had not been cleared despite the local authority knowing about the issue since 2007.
Independent highways consultant Alexandra Luck said it amounted to an “unacceptable failure to have any proper regard for highways safety”.
A pathologist said Miss Wright, from Henfield, died of neck injuries in the crash on February 18, 2010.
Forensic crash investigator PC Andrew Wilson-Law said it was “possible, indeed probable” that Miss Wright may have aquaplaned.
The hearing was told that ten days after Miss Wright died, experienced driver Sergeant Andrew Bradford aquaplaned at almost exactly the same spot.
He said he was “horrified” because he crashed through the flowers left in tribute to Miss Wright.
Stuart Smith, who at the time was highways maintenance manager for the council, said since the crash they have improved procedures.
Mr Smith said at the time of the crash the highways department had prioritised pothole repair following a harsh winter.
He said it was “difficult to understand” why the three gullies were not cleared when the issue had been reported to them for three years.
The coroner recorded a narrative verdict.
She said: “Three of the gullies at the scene had been noted as jammed and silted up on at least three occasions prior to the accident but inadequate maintenance had been undertaken.
“It was possible that this led to Chloe's car aquaplaning in those conditions directly into the path of the other vehicle.”
A council spokesman said: “All the evidence was explored at the inquest and we cannot comment on the verdict of the coroner.”
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