Business leaders have called for investment in the A14 in Suffolk to end delays they say cost £360m a year.
They have identified seven “pinch points” on the east-west trunk road where congestion could be eased.
More than 150 businesses are urging the government to invest in the route which ends in Felixstowe, the country’s biggest container port.
A Department for Transport spokeswoman said it would “continue to consider proposals for future enhancements”.
The businesses believe the upgrades could attract investment in other parts of the local economy and lead to the creation of 36,000 new jobs.
Mark Pendlington, of the A14 Strategy Group, said: “We are saying to the government: if you spend £150m investing in our section of the A14, our businesses and our economy will benefit by £1.5bn.
“That is a rate of return on that project like no other in the UK that I can think of.”
The group wants seven locations near Ipswich, Newmarket and Bury St Edmunds to be improved over the next five years.
Highways England is currently in the middle of a £1.5bn upgrade to the A14 between Cambridge and the A1.
“What’s the point of spending all that money in Huntingdon to have traffic then grind to a halt in Suffolk?” said Mary Evans, a Conservative member of Suffolk County Council.
More on the Cambridgeshire A14 development:
Trevor Tyrrell, from agricultural machinery manufacturer Claas, based on the A14 just west of Bury St Edmunds, said regular delays came at a “severe cost” to customers.
“Directly to us it’s maybe £100 an hour for a truck, but the cost downstream is much more,” he said.
A spokeswoman at the Department for Transport said: “We are making a major investment in improving roads in the region, including the £1.5bn improvement to the A14 between Cambridge and Huntingdon.
“We continue to consider proposals for future enhancements.”