Cows grazing on common land in Gower are being given reflective collars to prevent them being hit by cars.
The collars are aimed at making the cows more visible at night
Cattle, sheep and ponies are regularly killed or injured by motorists on the open heathlands.
The Gower Commoners' Association said in one three month period, 90 animals died as a result of traffic accidents.
It has campaigned for lower speed limits on main roads and said the collars would protect the animals and highlight the danger to motorists.
So far around 40 collars have been placed around the necks of cattle grazing on un-fenced land.
The specially designed reflective collars have been paid for by the Gower Society and commoners.
Siôn Brackenbury, of the Gower Commons Initiative (GCI), said: "The collar is placed around the necks of cattle so that they can be seen from a distance at night. Although this initiative is welcome, it should not replace responsible driving."
Cattle, sheep and ponies roam freely on the unfenced land
He said cattle and other livestock grazing on the land ensured it was maintained and able to sustain other wildlife.
GCI has campaigned to have speed limits reduced on the commons at Fairwood, Pengwern and Cefn Bryn.
Mr Brackenbury said drivers as well as animals had been injured following accidents on the roads.
And he stressed only some cattle now had reflective collars and that they had not been put on sheep on ponies.
"Our message is kill your speed and drive with care across the commons," he added.