Signs which reduced the previous 40 mph limit to 30 mph were officially unveiled last Friday, signalling the completion of a £500,000 road improvement scheme which began in November.
The package of measures put in place by Hampshire County Council included the construction of the new roundabout, cycle lanes, a toucan crossing, an equestrian crossing facility and better street lighting.
Sgt Steve Blencoe, of Whitehill police, said that the police supported the speed reduction and would be enforcing the new limit vigorously.
He said: "This speed limit really is long overdue. It is a speed check area and we will be continuing to monitor the speed of traffic along that stretch of road."
Sgt Blencoe said that the stretch of road between the Whitehill roundabout and Conde Way roundabout was an area which is particularly used by pedestrians who live near Whitehill Village Hall.
"We have a lot of elderly people who live around here," he said. "They cross that road regularly to go to the post office, the pub and to the shop."
The sergeant also welcomed the footpath constructed from Whitehill roundabout up to the site of the Whitehill Club.
A spokesman for the county surveyor's department told The Herald that "only remedial work" was needed this week and he expected the contractors would be finished by this weekend.
Included in the remaining work was the emphasising of the two new "gateways" which mark the start and finish of the new speed restrictions.
He said: "The scheme was developed through a steering group set up by the county council and included members of Whitehill Town Council, officers from Hampshire County Council and East Hampshire District Council, Hampshire Police, East Hampshire Cyclists Forum, the British Horse Society and the Hampshire Association for the Care of the Blind."
The spokesman said that he was aware that some drivers had been affected by traffic delays during the bulk of the scheme, but he hoped they will feel that it was worth their wait.
"The safety scheme, the biggest in the county council's budget this year, comes after numerous accidents at the junction, totalling at least 12 which involve injury over the last three years.
"We have had particular problems with northbound traffic which travels along the long straight stretch of road before coming into Whitehill, and would still be travelling fast when it got to the Whitehill crossroads.
"However, they now have to slow down for the roundabout."
The safety scheme in Whitehill is one of a number of changes made to the A325 which has been dubbed "the most dangerous road in east Hampshire".
Other recent changes include the construction of the Sleaford traffic lights in 1999 and a number of speed limit reductions from Bucks Horn Oak to Wrecclesham earlier this year.