Dublin City Council has warned that all through traffic may have to be banned from the city centre because of congestion and construction projects.
A consultation paper says the number of commuters is projected to nearly double and that there is no room for more cars on city centre streets.
The warning comes as the council prepares a new development plan for 2011.
The planning department states that the number of commuters entering the city is projected to nearly double to 375,000 people by 2020.
It says there is no more capacity on the city's roads and that traffic modelling has shown that it may be necessary for through traffic to be removed to allow the city to function.
This could mean access only for motorists in the city centre and with other traffic forced onto orbital routes.
The paper states this proposal is particularly relevant because of Transport 21 construction projects. Metro North is due to start in two years' time.
The paper does not mention the possible effects of the economic downturn on its projections.