Work has begun to transform Hemel Hempstead’s Old Town into a one-way system.
The £1.3 million project, part of planned regeneration of the area, is expected to last five and a half months.
The change will mean drivers can only pass through the Old Town from Queensway heading up the High Street.
Work will be carried out in five phases by civil engineering contractor Jackson on behalf of Dacorum Borough and Herts County councils.
Phase one, which involved preparatory work, began on May 28 while the second phase, implementing the one-way system, starts on Monday.
The second and third phases will require traffic control in the area but vehicles can continue to drive along the road.
However, phase four will lead to a closure of the High Street from September 2.
Leader of Dacorum Borough Council Andrew Williams said: “The new one way system is part of our wider regeneration plans for the Old Town and will help to make it easier for people to visit by reducing congestion and easing the flow of traffic.”
County Councillor Terry Douris, who oversees highways, transport and waste management, said: “We are sorry for any inconvenience caused by these works which are a key part of the regeneration of the Old Town.
“Disruption will be kept to a minimum but we would ask you to allow extra time for any journeys you make while the work is in progress.
Hemel Hempstead MP Mike Penning has been calling for the changes for eight or nine years.
The work has been subject to delays as the one-way system was originally expected to have been up and running by late 2011. The Gazette last reported that it was due in April this year at the latest.
The car park off High Street will remain open throughout the works.
Contact details and regular updates, including photos of the work in progress, will be posted on the borough council’s website at www.dacorum.gov.uk.
Visit www.hertsdirect.org/roadworks for more details about the works and road closure information.