A team from Glasgow University found there was a sharp fall in accidents from 5,901 in 1997 to 2,914 in 2014.
The researchers said, however, there was "no evidence" the M74 had impacted on an "already decreasing trend".
The five-mile (8km) route, which cost Â£692m, links the M74 at Carmyle to the M8 southwest of the Kingston Bridge.
Planning permission for the route was granted in October 1995 and immediately opposed by Joint Action Against the M74 (Jam74) - a coalition of community, environmental and sustainable transport groups.
Construction began in 2008 after a last-ditch legal bid to halt the project was abandoned by Friends of the Earth Scotland and Jam74.
Supporters claimed the road would bring economic benefits to the west of Scotland and help cut accidents, whereas critics argued it would cause more pollution, increase health problems and fragment communities.
The Glasgow University study looked to evaluate the impact of the M74 extension on the number of road accidents on local roads during the construction period and following its opening.
Lead author of the report, Dr Jonathan Olsen, said: "The building of the M74 extension in the south of Glasgow was controversial. There were strong arguments for and against its construction, but ultimately it went ahead.
"One of the arguments in favour was that it could reduce road accidents on local streets.
"In our study we examined police accident data from 1997 to 2014, three years after the new motorway was opened, and found that this predicted reduction in road accident numbers had not materialised."
He added: "But on the other hand, we found no evidence that the M74 extension had led to an increase in accidents."
Report co-author, Professor Rich Mitchell, added: "There is surprisingly little evidence about the impacts new motorways have.
"This research will be useful for planners, politicians and residents elsewhere who are trying to decide whether to build or not."
The study is published in the Journal of Epidemiology and Community Health.
The controversial M74 extension through Glasgow has had little impact on road traffic accidents in the city since it opened in 2011, a new study has found.