Traffic on Whanganui's Virginia Rd is being diverted while a raised platform and speed bump is installed between Brassey Rd and Porritt St.
A council spokesman said Virginia Rd had been identified as being in the top 10 per cent of dangerous roads in Whanganui.
"The work forms part of the country's road safety strategy in conjunction with Waka Kotahi NZ Transport Agency's Road to Zero campaign to reduce speeds and lessen fatalities and serious injuries."
Work began on Monday and detours will be in place for 24 hours a day until 5pm on Wednesday, March 16.
Traffic entering Halswell St and travelling towards Great North Rd will divert into Porritt St, Oakland Ave and Brassey Rd to bypass the worksite.
For Great North Rd traffic travelling towards Halswell St, one side of Virginia Rd will remain open.
Residents and emergency services will be able to access properties within the worksite from Brassey Rd only. Tulloch St will remain open in both directions but traffic will only be able to exit towards Halswell or Porritt Sts. Detour and speed reduction signs will be in place during the work.