It’s difficult to see how alternative transport can alleviate the traffic in this area.
There’s already a regular coastline train service serving all the towns along the Sussex coast. There’s a coastline bus service.
It’s never going to be a popular cycling route (hills, fast traffic...
Don’t agree with you or Zack on nimbyism
Ultimately this, and every country, needs a certain amount of infrastructure. Some of it is relatively desirable, ie post offices, shops, doctors .. Some of it less so, eg sewage works, asylum centres, dual carriageways.
Now individuals might not...