Taxis will no longer be allowed to use New Street and New Cut.
The Infrastructure Minister is removing access across King Street for buses and taxis for at least the next year
The 12 month trial is part of moves to give pedestrians priority.
The government says a recent traffic survey revealed that half of vehicles using the route during core shopping times (10am-4pm) were taxis, with buses making up 8% of traffic volumes.
"Removing taxi access southbound from New Street to Library Place and rerouting buses will support pedestrian safety and reduce congestion."
Only pedal cycles and essential deliveries to shops after 8pm and before 10 am will be allowed.
Library Place taxi rank remains.
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