New research has found that the number of serious accidents on the A259 has gone up by 50 per cent in the last five years.
According to Save Our Harbour Villages (SOHV), which is a campaigning organisation fighting the potential effects of housing over-development through Chichester harbour villages, the findings mean the A259 is 'twenty times more dangerous' than the A27.
A spokesman said: "The A259 is already ranked 30th most dangerous road in the UK (Department of Transport 2018), but new research shows a steady growth in traffic has made it a lot more perilous in the last few years.
"Local residents in Southbourne, Chidham, Hambrook and Fishbourne have long been saying the A259 local harbour road has had an increasing number of accidents."
SOHV reviewed data compiled by Crashmap.co.uk, which tracked all vehicle accidents on UK roads over time.
The spokesman continued: "SOHV looked at A259 versus A27 accidents between Warblington and Fishbourne roundabouts (eight miles).
"The shocking revelation is that, whilst the average number of serious accidents on the A27 has stayed the same, the number on the A259 has gone up 50 per cent during the last five years. The local A-road also now has nearly three time more deaths and serious injuries than on the A27.
"As the A27 takes eight times the amount of traffic per hour, it makes the comparative danger even greater on the A259."
SOHV campaigner Andrew Kerry-Bedell said that, statistically, for every mile anyone in a vehicle travels on the A259 from Fishbourne to Havant, they are 'twenty times more likely' to be killed or seriously injured than on the A27.
SOHV found that the speed of vehicles 'wasn’t the main issue'.
The spokesman explained: "The only 60 mph section had only one serious accident in the last five years. In contrast, almost three quarters of all vehicle accidents occurred at the road junctions that feed into the A259, particularly in the 30 mph zones through Chidham, Emsworth and Southbourne.
“With modern cars getting safer by the year, the data shows it’s the extra traffic that’s the main issue. With people living in new housing there’s a lot more cars on all roads feeding into the A259. And this is only the tip of the iceberg as the data only shows injuries in vehicles.
"Residents have plenty of instances of more pedestrians and cyclists being injured from the increase in local traffic.”
SOHV said the findings call Chichester District Council's local plan into question.
"This is just one of the reasons many harbour village residents are questioning the wisdom of large amounts of new housing along the A259," the spokesman said.
”The A259 is the local east-west alternative to the A27, and the lifeblood of harbour villages. It used to be quiet but we’ve shown it’s now become far more dangerous, and that’s with only the 16 per cent increase in new houses that were built in the last five years.
"Imagine what the extra 46 per cent of new houses in the council plans will do to the rate of serious accidents.”