The single-lane bridge over the Cuckmere river on the A259 between Eastbourne and Seaford regularly has long queues of traffic on both sides.
Many visitors to Seven Sisters Country Park, Beach Head and Birling Gap on the East Sussex coast use the route.
A government grant is to be used to build a new two-lane crossing.
East Sussex County Council said it would chose a location for the bridge which minimises the impact on South Downs National Park.
Traffic can only cross the existing bridge in one direction at a time. Priority is given to vehicles travelling from the west, causing long delays for those waiting to cross from the Beach Head and Birling Gap side.
Councillor Rupert Simmons, lead member for economy, said: "As well as being frustrating for motorists, the bottleneck does nothing to help the businesses in our county.
"We have considered a number of options to deal with the problems at Exceat, including traffic lights, but it is felt that a new two-lane bridge is the only way to effectively deal with the congestion created by the current layout.
"The location of the new bridge is a sensitive one and will need to be carefully designed to minimise the impact it has on the South Downs National Park in which it sits."
Any proposals will be subject to discussion and approval from the South Downs National Park Authority (SDNPA), the council said.
A spokesperson for the South Downs National Park Authority said: "As the planning authority for the South Downs National Park, we would welcome pre-application discussions with East Sussex County Council as they develop their plans.
"Any application that comes forward will need to be of a high quality, taking into account both this sensitive location; the people who know and use this area, and the special qualities for which the national park was designated."

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His side have won only two of their first seven league games following promotion and lie in seventh place.
"What I said at the start of the season, and I was very, very clear, was that we'd be highly competitive," the English manager told the media.
"You guys said about challenging Celtic and challenging Aberdeen."
Rangers are seven points behind reigning champions Celtic and three adrift of the Dons, who were last year's runners-up, after losing to both in recent weeks.
"I said we'd be highly competitive and that won't change," he said of a side beaten 2-1 at Pittodrie in their last outing.
"I think you saw on Sunday we were highly competitive, but we have to get the rewards for it.
"What we have to do is to turn our domination and ball possession into rewards.
"That's what we did against Queen of the South. Between the Ross County and Queens match, there was no difference between the displays, but in one game we were far more clinical than the other."
Warburton, who has received a one-match touchline ban for comments made after the loss to Aberdeen, insists it is still early in the season to express disappointment at Rangers' league position.
"You can say you are four points from the bottom or three points from second," he said ahead of Saturday's Glasgow derby against Partick Thistle.
"At this stage of the season, in any league, you win two games and the whole picture changes. The same if you lose two."
A bottleneck on a popular tourist route along the south coast is to be tackled with a new £2m bridge.
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Mark Warburton says his goal at the start of the season was simply to be "highly competitive" in the Scottish Premiership and Rangers have done that.