Officials at the Freight Transport Association say it is "unacceptable" that improvement work on the A46 in Nottinghamshire has been delayed.
They say work to make the 17-mile (28km) stretch between Newark and Widmerpool a dual carriageway should start in 2008 but has now been delayed until 2012.
The association said the road is a key trade route and should be a priority.
Ministers should announce a start date for the work later in the year.
The start date was put back after the government carried out work to identify regional transport priorities.
Geoff Dossetter, the FTA's external affairs director, said: "It is a vital route and congested during large parts of the day, which is inconvenient to motorists and industry.
"The road safety hazard is a major issue.
"The fact that there have been so many fatal accidents over the years means that the time has come to get on with this road and to dual it now as quickly as possible."
A spokesperson from the Department of Transport said he could not speculate on what date the work would start.
He said ministers were still considering advice and consultations carried out in the region.