The Transportation Department issued a request for proposals Friday for an estimated $1.5 million study of more than 300 kilometres of 100-series highways.
Transportation Minister Geoff MacLellan said tolls are being considered because the government can't afford to twin under its existing infrastructure plan.
"Given the interest and the support for looking at twinning this is really the only way it's financially viable," said MacLellan.
He said the government would not use tolls unless the public indicates it wants them as a result of a planned consultation process.
MacLellan said the final report, which will include the results of the public consultations, is expected to be completed by the end of next April.
Among the sections of road to be studied are Highway 101 between Hortonville and Coldbrook, Highway 104 between Sutherlands River and Antigonish, Highway 103 between Tantallon and Bridgewater and Highway 107 between Porter's Lake and Bedford.
MacLellan said even if the study finds that tolls aren't wanted, the information gathered will be useful for long-term highway planning.