Measure designed to make it easier for drivers to cross the four cross near Les Bourgs Hospice Shop.
The filter in turn markings are being painted on the junction of Brigade and Variouf roads where they meet the Corbinerie and the lane that heads towards the back entrance of Les Bourgs Hospice Shop in St Martins.
It means the junction is expected to be closed for most of today, Saturday 12 July.
The States say the move is in response to feedback from drivers, who find it testing to get adequate visibility to cross the main roads that link the Old Forge area with Bailiff's Cross.
They say the road is especially busy on weekdays and there have been collisions reported as well.
Paul James is a road safety officer with Traffic and Highways:
“This junction meets the threshold for installing a filter, bringing improved road safety with minimal impact on traffic flow.”
Guernsey's Victor Hugo Centre reaches fundraising milestone and unveils sculpture
Guernsey's police complaints process not 'in crisis'
Guernsey could be disgraced Andrew’s new home - Royal biographer
Guernsey Museums close for the season
First visit of an EU ambassador to Guernsey
Hotel guests help grow a greener Guernsey
Guernsey man seeks donations after 2,000-mile challenge
Charity funds upgrades at Guernsey swimming pool
