The National Transport Authority says it plans to examine how it can give more priority to buses, and that may come at the expense of drivers.
It follows radical lane changes and the banning of private cars turning right onto O'Connell Bridge in August.
New research into Quality Bus Corridor routes in Dublin shows it's taking longer for passengers in certain suburbs to get into town.
Last year cars were faster travelling in from Clondalkin, Tallaght, Bray and the Malahide Road than Dublin Bus.
Journey times from Lucan and Finglas took even longer in 2016 than the year before.
It's being blamed on having to share the road with ordinary car traffic for up to thirds of the route, at a time when congestion in the city is getting even worse.
€750m has been ring-fenced by the government for transport next year and the National Tranport Authority says it plans to use some of that to tackle the problem.
CEO Anne Graham admits that may be at the expense of cars in some cases
"It could be that a lane of car traffic may have to be given up for bus or for cycling... (The measures) could also inlcude looking at the car lanes, the loss of parking, some road widening and changing signals at junctions to improve the priority."
It wasn't all bad news though with 12 bus routes showing improved journey times last year.
They inlcude the 42 from Portmarnock which, from Swords, flew into town eight minutes faster in 2016 than the year before.