Hard shoulders on parts of motorways should be turned into carriageways to ease traffic congestion, a report on Northern Ireland's roads has said.
Consultants estimate the project could cost between £60 and £70m if adopted.
Roads authority Transport NI asked experts to examine creating additional capacity on motorways due to "recurrent traffic congestion at peak times".
Their report suggested the M1 and M2 in and out of Belfast become so-called "smart motorways".
Similar schemes are already in operation in England.
The hard shoulder on each side of the M1 between Stockman's Lane and Blaris would be turned into traffic lanes.
On the M2, the hard shoulder would be converted to carriageway on both sides between York Street and Greencastle.
A summary of the report, seen by the BBC, said the idea was at the concept stage but was considered "value for money".
It highlighted that one drawback could be that it may encourage car use at the expense of public transport.
The Freight Transport Association, which represents haulage firms, said the idea should be "given serious consideration."