A relief road has taken a major step towards completion but traffic problems remain along the stretch.
West Sussex County Council has opened stage six of The Haywards Heath Relief Road project linking the B2112 Wivelsfield Road with the A272 Lewes Road.
However, police officers warned motorists on Monday of “horrendous” traffic along the route because of more roadworks.
The road, which includes new roundabouts at Fox Hill and on the A272 Lewes Road, cost £6.8m and was funded by developer Crest Nicholson.
The new road will eventually become part of the A272 once stage five of the relief road, which links Bolnore Village to Rocky Lane, is completed.
Stage five is under construction and is expected to be completed by summer 2015.
However day one of the new route proved little relief to motorists travelling through Hawyards Heath on Monday.
Work began at the start of this week along the A272 between The Broadway and Bolnore Road to allow Gas Transportation Company to remove electrical cables.
The work is scheduled to run until November 28.
Sussex Central Road Policing Unit tweeted: “Traffic in Haywards Heath horrendous as a result of A272 roadworks. Unless you want to sit in queues for long periods: avoid!
“It's every bit as bad as anticipated so far. Very long queues in all directions.”
Councillor Pieter Montyn, cabinet member for Highways and Transport, said: “Opening this section of new road to the public is like fitting the penultimate piece in a jigsaw.
“We now look forward to Stage five being finished at the earliest opportunity.
“About eight million vehicles journey through Haywards Heath town centre each year, so once the new road opens it will act as a release to all the traffic pressure there.”
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here