Ten weeks of road disruption and closures are set to take place around a busy junction in Balcombe Road, from June 8.
Work will be carried out under traffic lights for two weeks then the entire stretch of the road will be closed from June 22 for eight weeks.
The closure will be in place 24 hours a day.
Motorists will need to find alternative routes throughout the duration of the works.
West Sussex County Council will host a public drop-in today at Haywards Heath Town Hall, in Boltro Road, from 4pm to 6pm, for people wanting to find out more about the improvements.
The work, particularly around the junction with Old Wickham Lane, has been planned to make the stretch - north of Haywards Heath centre - safer to cross.
Some footways in Balcombe Road will be widened, the existing footways will be resurfaced and the northern end of Barnmead will be narrowed.
A diversion will be in place via Hanlye Lane and Cuckfield.
John O’Brien, county council cabinet member for highways and transport, said: “The local community in this area of Haywards Heath have desired this safety improvement for some time, so we are happy we now have a suitable opportunity to provide it for them.
“This is a busy road – one of the main routes into Haywards Heath from the M23 – so there will be some disruption.
“We just ask people to bear with us while the work gets done.”
The workmen will be on site six days a week - with a rest on Sundays.
The scheme gained full support from the Mid Sussex County Local Committee in 2012.
Officers will be available to answer any questions about the scheme at the public drop-in event today (Thursday May 28).