New road capacity is needed to avoid 1,000 miles of major routes becoming gridlocked, a report has warned.
Building 372 lane miles of road will yield benefits, the report says.
Roads most at risk from severe congestion include the M25 and routes around Birmingham and Liverpool, the RAC Foundation study said.
The report called "Roads and Reality" says more roads are essential whether or not the government introduced national road pricing.
Building 372 new "lane miles" would "yield substantial benefits," it said.
'Greener and cleaner'
The figure is the equivalent of building one extra lane of 372 miles in length.
Road pricing without road building will just drive poorer people off the roads, the report added.
By 2041, car ownership will be 44% higher and car traffic will increase by 37%, it said.
It also said that cars would continue to get greener and cleaner towards 2050.
The government has "some tough choices to make" to avoid severe congestion by 2041, the report added.
It said national road pricing would help to get the most efficient use out of the system but it was not a substitute for investment in new roads.
RAC Foundation chairman David Holmes, said the report was an "authoritative" contribution to the government debate on transport policy and investment.
"Our children and grandchildren will not accept poorer standards of service from transport than we have today.
"This report shows how we can meet the needs of people for mobility and access, while also protecting the environment."
One of the report's authors, Professor Stephen Glaister, of Imperial College, London, said: "The modelling suggests that the government cannot use the possible future introduction of road pricing as a reason to ignore the need to improve the strategic road network.
"If national road pricing has been put on the back-burner, more urgency is required for intelligent investment decisions now to keep the county moving in the future."