Rouge Bouillon is closed to through traffic until 9pm on 1 November between the Queen's Road roundabout and Parade Road junction.
It's so that stretch of the road can be resurfaced. St John's Road is being temporarily made one-way southbound.
Work is being split into two sections to help the emergency services. The first is between Jersey Fire & Rescue HQ and Queen's Road roundabout and the second is between the HQ and Savile Street.
The government says this is happening during the school holidays to minimise disruption to nearby residents and businesses.
More details, along with maps of the work and diversions in place, can be found here.