The controversial Quality Bus Corridor (QBC) between Foxrock Church and St Stephen's Green was due to open this morning, despite last-minute calls for its postponement.
The AA said the already congested traffic on the route would be made considerably worse by the introduction of the measure, and again called for it to be delayed.
At Donnybrook, one of the two existing lanes for ordinary traffic in each direction will be occupied by the 10-kilometre QBC, which will operate from 7 a.m. to 7 p.m, Monday to Friday, leading to fears of congestion.
The AA spokesman, Mr Conor Faughnan, said the full implications of the introduction of the QBC would not be known until the middle of September, as parents bringing children to school would add considerably to the number of cars on the roads.
The Fine Gael spokeswoman on traffic, the Dublin South TD, Ms Olivia Mitchell, also made an eleventh-hour call for the corridor to be postponed.
"If this project goes ahead as planned the traffic across a wide swathe of south Co Dublin will come to a complete standstill," she predicted.
Calling for the introduction of feeder buses to serve the corridor, Ms Mitchell said most users of the Stillorgan Road did not live within walking distance of it and could not access the bus service, no matter how frequent it might be. "This half-baked effort will only reduce confidence in public transport at a time when travellers are being actively encouraged to use it," she said.
"The Minister for Transport should address this issue urgently instead of attending fruitless and time-wasting public relations opportunities for Luas, which won't come on line for years."
The Society of the Irish Motor Industry (SIMI), in a strongly-worded statement, said the politicians of Dublin, Wicklow, Kildare, Meath and Louth "would be well advised to remember that car-owners have votes".
The society said "the objectives of a QBC are not being met and current traffic policy presupposes the presence of a good public transport system and facilities, which are simply not there."
The society said the new measures would represent an unreasonable burden on people who lived outside Dublin in new developments, who had little choice but to use their cars.
The Chartered Institute of Transport in Ireland said the success of the QBC would depend on the quality of the Dublin Bus service and would also require a "mindset change" on the part of motorists living near the corridor.
The institute, which is an independent body for transport firms, said the credibility of the QBC concept would be undermined unless Dublin Bus could guarantee a regular and efficient service at all times of the day.
But the institute went on to criticise motoring organisations for their "negative attitude displayed towards the QBC."
"Instead of stating that the QBC will cause massive disruption, these organisations should be urging city-bound car commuters, the main cause of peak-time congestion, to reappraise their travel habits by using the service," said a spokesman.
"This applies particularly to motorists who live in areas adjacent to the route and for whom the provision of park-and-ride facilities is not an immediate issue."
