Two York streets will be closed for six weeks so bollards can be installed.
Both High Petergate and Lendal will shut at 7.30am on Monday (24 April) and be closed until 7pm on 2 June.
They are closing for ‘hostile vehicle mitigation barrier work’.
Sliding and fixed bollards will be installed in High Petergate and Lendal, with other permanent barriers following from May onwards.
A City of York Council spokesperson said: “While doing everything to maintain access for everyone in the city centre, there will need to be occasional diversions.
“Residents and businesses will be kept updated on work which will affect them, and the work is planned to be finished ahead of the busy Christmas market.”
Once installed, the bollards will allow mobility scooters, wheelchairs and pedestrians through, as well as deliveries by foot and hand cart, and vehicles will be allowed outside footstreet hours.
Detective Superintendent Dan Patrick, regional head of protect and prepare at Counter Terrorism Policing North East, said: “These physical security measures are a vital, precautionary step to protect people visiting, living and working in the city.
“Unfortunately, the threat from terrorism remains very real, and recent incidents demonstrate that attacks can happen anywhere, and without warning.
“Areas of high footfall remain a potential target and this includes city centres, entertainment venues and attractions across the UK.
“York is not exempt from this threat, and it is essential that we take all necessary precautions to protect the public and make the city a less attractive target for terrorists.”
Labour transport spokesperson, Cllr Rachel Melly said: “Of course Labour does not oppose the introduction of anti-terrorist barriers, but is completely opposed to banning Blue Badge holder access to the city centre.
“Independent experts have confirmed Blue Badge holders could easily have access without hazard to public security while council officers have confirmed a workable scheme is possible that allows improved access to the current one.
“Recent years have shown plenty of vehicle access permitted other than that for Blue Badge holders. Ruling Liberal Democrat Party and Green councillors have been inconsistent in who they have banned and discriminatory in the decision they have taken.
“If Labour are elected on May 4th we will enable everyone to safely access the city centre, including our disabled residents and visitors”.