Business leaders say they are worried about the economic impact of a decision to scrap the proposed M4 relief road.
Outlining a five-year transport plan, Transport Minister Ieuan Wyn Jones said on Wednesday the plan had tripled in cost to £1bn and was "unaffordable".
However, CBI Wales, the Federation of Small Businesses and Chamber Wales said the road was the "most important scheme needed to take Wales' economy forward".
Campaigners against the road called it "excellent news" for the environment.
Mr Jones announced spending of between £64m and £110m to improve the existing M4 network instead.
He also scrapped a planned Cardiff Airport access route.
NATIONAL TRANSPORT PLAN
£1bn M4 relief road around Newport rejected but up to £110m to be spent on improvements in the area
New road to Cardiff airport rejected but more frequent bus and train links
"Sustainable travel towns" - three more on Cardiff model
Emphasis on healthy, sustainable transport, such as walking and cycling
Improved local bus services
Improved rail services, including improved rolling stock, Ebbw Vale to Newport link by 2011, and north-south link through Wrexham
Other improvements - including expanding TrawsCambria long-distance bus network and car-sharing
Source: Welsh Assembly Government
The business groups said the M4 relief road would have created a strategic route into the south Wales economy.
David Rosser, director of CBI Wales, said: "The M4 is the artery that feeds the economic heart of Wales and it is becoming choked.
"Successive governments have planned and then put off the implementation of this key piece of infrastructure."
Paul Rutter, chair of Chamber Wales which represents chambers of commerce, said the planned improvements would help in the short term but were "not sufficient for the long-term economic needs of Wales".
The FSB's Russell Lawson added: "Time is money for a small business and we need government to provide us with a fit-for-purpose business environment that includes a well-functioning road network."
Meanwhile, the Freight Trade Association said the future of the south Wales economy was "severely hamstrung" without the relief road.
Spokesman Jo Tanner said: "It is bitterly disappointing that despite industry's best efforts to convey the importance of better traffic flows in and out of Wales to its economic well being, there is no apparent compulsion amongst the assembly government to invest in Wales' future."
However the Campaign Against the Levels Motorway (Calm) group said the Gwent Levels, which the road would have been built through, had been saved from the "concrete pourers".
"The motorway has cast a dark shadow for decades over the wildlife-rich Gwent Levels, and... [this] is an excellent result for the environment, and the Welsh tax payer," said Calm chairman James Byrne.
"We believe that better use of existing road capacity and investing in improved public transport in south east Wales can achieve as much, or more at a much lower cost to the environment and Welsh tax payers."
He added road transportation produced almost 14% of Wales' greenhouse gas emissions.