In September, blue paint was used on a sample of privately-owned Dartmoor ponies to test its durability.
Conservationists said it had remained on the animals, and reflective beads that create an "alien glow" had since been added.
They said 74 animals have been killed so far this year on Dartmoor's roads.
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Karla McKechnie, livestock protection officer for the Dartmoor Livestock Protection Society (DLPS), said: "The reflective element is very bright and despite the horrendous weather it's very visible.
"We'll now monitor how long it remains on the animals, and the company behind the paint is trying to see whether it can create an even brighter and more durable version."
Ms McKechnie said following the success, the plan was to paint moorland livestock ahead of Dartmoor's annual pony round-up and sale, known as the drift, which is held each autumn.
"She told BBC News: "In the coming months we might try the reflective paint on privately-owned cattle too.
"The moor is a working landscape and the animals are the priority," she added.
Rob Steemson, Dartmoor National Park's head ranger, said: "The authority is pleased to hear the trial is progressing well and we continue to fully support the project to reduce the number of road deaths in conjunction with educational messages for motorists using Dartmoor's roads."
Source: Dartmoor National Park Authority/BBC News
Reflective paint, which could "save hundreds" of animals from being killed by vehicles, has been put on ponies after a trial was deemed a success.