Villagers fear a proposed £4 million bus corridor along a busy coastal road will cause traffic chaos and force motorists and cyclists dangerously close to the cliff edge.
Some residents on the A259 between Ovingdean and Telscombe Cliffs could also be made to give up their gardens under compulsory purchase orders to enable road widening.
The scheme is a joint initiative between East Sussex County Council and Brighton and Hove City Council aimed at speeding up traffic along the main South Coast Road and encouraging greater bus use.
It involves the creation of bus and cycle lanes, with buses having priority over cars at all times, including traffic lights.
The scheme is opposed by Rottingdean Parish Council, the local traders' association and seafront residents.
Rottingdean Parish Council chairman Peter Hampton said the scheme was "environmentally calamitous" and has written to the two councils warning that in some areas the cycle track would run too close to the cliff edge.
He said some "pinch points" along the route could mean residents losing their front gardens.
Harold Williams, chairman of the Rottingdean Trade, Business and Professional Association, said: "It will do little to ease the ever-increasing traffic congestion, particularly during the morning and evening rush hours.
"The introduction of bus lanes will have a negative effect.
"It may give rise to speedier bus transit on certain stretches of the A259 but the whole concept will be thwarted by unavoidable bottlenecks such as central Rottingdean, particularly as it might involve the loss of grass verges and the reduction of front gardens under compulsory purchase orders, which we deplore."
The scheme has been on the drawing board for five years.
If it gets the go-ahead, work is expected to take two years, leading to lane closures and traffic hold-ups.
Key to the success of the scheme is traffic unblocking at Rottingdean traffic lights, where queues build up for up to a mile each side of the lights at morning and evening rush hours.
The proposals do not include any major road widening at Rottingdean traffic lights but there is a proposal to phase the traffic signals to allow the buses to go ahead of the traffic, so they clear the junction first.
Brighton and Hove City Council and East Sussex County Council insist the scheme is at an early discussion stage, no decisions have been taken and concerns of residents will be taken into account.
Gill Mitchell, chairwoman of Brighton and Hove Council's environment committee, said: "By separating the traffic flows it will save cars being stuck behind buses and may persuade more people to use public transport.
"Yes, the road may have to be widened in parts but the needs of pedestrians will be taken into account and may even be enhanced.
"And if seafront bus lanes do go ahead and are successful, it could lead to extra feeder bus routes from residential areas."
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