The speed limits have been cut on 17 roads in St Mary, St Lawrence and St Peter.
The new limits come into force this week.
Among the changes, a 40mph road through St Mary's Village, including Le Clos de I’Arsenal, has become a 20 zone.
La Grande Rue, La Rue Rondin and leads into Le Mont de Ste Marie, La Rue de la Frontière which leads into St Lawrence’s Les Chanolles des Six Rues, which were all 40mph zones, are now 30mph.
12 roads have been given 'Green Lane' status, meaning they now have a speed limit of 15mph. Some of these previously had a limit of 40mph.
- La Chève Rue
- The northern end of La Grande Rue by The Priory
- La Rue à Georges
- La Rue Bechervaise
- La Rue du Douet
- La Rue ès Boeufs
- La Rue ès Viberts (In both St Mary & St Peter)
- La Rue du Couvent (In both St Mary & St Lawrence)
- Le Jardin du Couvent
- Le Clos des Buis
- Le Mont Remon (St Peter)
- La Verte Rue (St Lawrence)
The reductions are part of the wider Island Speed Limit Review, which is aiming to improve road safety.
Speed limits were lowered in the Infrastructure Minister's own parish of St John as part of the review last November.
Earlier this month, Ministers set out plans to halve the number of road deaths and injuries in Jersey.
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