The A259 runs east from Emsworth in Hampshire, into West Sussex via Chichester, Bognor Regis, Littlehampton, Ferring, Worthing, Lancing, Shoreham-by-Sea, into the Unitary Authority of Brighton and Hove which incorporates Portslade, Hove and Brighton, and on into the East Sussex towns of Peacehaven, Newhaven, Seaford, Eastbourne, Pevensey, Bexhill-on-Sea, Hastings and Rye.

Landmarks on the A259 include The Body Shop headquarters outside of Littlehampton, Shoreham Power Station, West Pier, and the Palace Pier in Brighton, Telscombe Cliffs near Peacehaven, and Saltdean, Cuckmere Haven between Seaford and Eastbourne and the Romney, Hythe and Dymchurch Railway which shares the route for 8 miles (13 km) from New Romney to Hythe.

In June 2008, a 12 miles (19 km) stretch of the A259 between Hastings and Eastbourne was named by EuroRAP as the most dangerous road in the South East of England.

In the summer, this can create significant congestion where goods vehicles between the towns mix with day traffic to popular holiday destinations such as Camber Sands.

It was extended westwards to Worthing after the local engineering division informed the Ministry of Transport they would like a single number to represent the coast road.

[16] This was provisionally signed off in July 2009 by the Department for Transport, with the caveat that individual schemes would still need to be assessed for value for money and compatibility with greenhouse gas emission targets.

[18] The county council said: "The driving force of the scheme is to enable essential economic regeneration for Bexhill and Hastings, which is currently compromised by the poor accessibility within and between the two towns... the Bexhill Hastings Link Road would make a major contribution to meeting the need to improve access between the towns and linking Trunk Roads which serve the area".

This sort of woodland is only found on steep sided valleys and are hugely important for wildlife but are highly sensitive to pollution.

They also believed it would create pressure to build a 'Hastings Eastern Bypass' which would pass through the High Weald Area of Outstanding Natural Beauty, which they claim is one of Britain's finest landscapes.

The Sussex Wildlife Trust "strongly" objected to the road stating that "the environmental damage that will result from this scheme is unacceptable and will alter the ecology of the Combe Haven valley for ever.