People who use North Strand Road to get into town should plan a different route on Saturday night and Sunday.
It's closing at Ossory Road to facilitate the construction of a bridge for cyclists at Newcomen Bridge.
The works are part of the proposed Sutton to Sandycove cycle route.
Local Independent Councillor Nial Ring says it's a particularly bad pinch-point for people travelling on bikes.
"(When it's built) to the left of the footpath, cyclists will take a small diversion of about 2 or 3 metres on to Ossory Road and will then cross safely on their own bridge and continue travelling down to the Five Lamps..
The traffic is very bad there in the mornings so this will be an added protection for cyclists."
The roads will be closed from 10pm on Saturday to 8pm on Sunday.
Here are the details of the city council's diversions: