The speed limit for lorries on single carriageway main roads in England and Wales will rise from 40mph to 50mph, the government has announced.
The move, affecting heavy goods vehicles weighing more than 7.5 tonnes, will come into force in early 2015.
The speed limit for cars on these roads is 60mph.
Motorist groups welcomed the change, but the Green Party said it would involve "greatly increasing the risk and severity of crashes".
Transport minister Claire Perry claimed the higher speed limit would cut congestion, reduce dangerous overtaking, and save road haulage firms £11m a year.
"This change will remove a 20mph difference between lorry and car speed limits, cutting dangerous overtaking and bringing permitted lorry speeds into line with other large vehicles like coaches and caravans," Ms Perry said.
"Current speed limits for HGVs were introduced around 50 years ago and need to be updated given improved vehicle technology."
Geoff Dunning, from the Road Haulage Association, welcomed the change. "The current limit is long out-of-date and the frustration it generates causes unnecessary road safety risks," he said.
The government is also proposing to increase the speed limit for lorries on dual carriageways from 50mph to 60mph.
Depending on the outcome of a consultation on the subject, this could also come into effect in early 2015.
The existing speed limits continue to apply until then.
AA president Edmund King said: "This seems like a common sense move.
"This 20mph speed differential can lead to bunching and dangerous overtaking manoeuvres. So we welcome the plans to allow trucks to legally travel at 50mph on these roads to end this frustrating, dangerous, historic anomaly."
Mr King said an AA/Populus survey showed that 81% of drivers did not know the legal national speed limit for lorries on single carriageway main roads.
"So it is no wonder other drivers get frustrated, perhaps thinking the lorry driver was just being awkward, lost or was trying to save fuel," he said.
"Smoother traffic flow also provides some economic benefit by improving journey times. We do appreciate that some have concerns about letting lorries travel faster but a more realistic limit should lead to better compliance by all."
Mr King said the AA would study the dual carriageway lorry proposal.
He added: "Lorries today are much safer than they were many decades ago and so it should be feasible for them to travel faster to help the economy and smooth traffic flow as well as reducing tailgating and crashes."
But Green Party transport spokeswoman Caroline Russell said: "The government say they want to reduce the speed differential between lorries and cars to improve safety, but their move to raise the speed limit for lorries ignores basic physics.
"Lorries are heavy and by increasing the speed at which they travel, the government is greatly increasing the risk and severity of crashes.
"By raising the limit for lorries they are also increasing the speed differential between lorries and vulnerable road users: people walking and riding on bikes or on horses.
"This is thoughtless and downright lethal for anyone getting about on rural roads under their own steam. "
RAC Foundation director Professor Stephen Glaister said: "For drivers there is nothing more dangerous than single carriageway rural roads, with two-thirds of car occupants dying on these types of route.
"The hope is that the raising of the limit will bring vehicle speeds closer together and reduce the temptation for people to overtake where they should not.
"We would expect the Department for Transport to closely monitor the change to make sure this is the case."
Cycling charity CTC's policy coordinator Chris Peck said the group understood this reasoning and the motivation behind the policy shift.
The majority of collisions between lorries and cyclists were at low speeds in urban areas, he added.
"But some are on A-roads. The move is not going to be good news for cyclists, and it is very likely to be bad news - increasing the risk of injury to cyclists, but also how safe cyclists feel on these roads, particularly when they are being overtaken at high speeds, with the turbulence that follows.
"There have been accidents where cyclists have been killed by being destabilised when drivers overtake too quickly."
Higher speed limits for lorries could therefore make accidents involving cyclists more likely, he said.