Players are recommended but not compelled to use StemGuards, developed by British manufacturer Masuri following the death of Phillip Hughes in Sydney in 2014, under CA's concussion and head trauma policy but Smith is among those who have felt the current guards are uncomfortable.

Smith was hit flush on the side of the neck by a rearing bouncer from England fast bowler Jofra Archer on a dramatic fourth afternoon of the second Ashes Test, when a neck guard - made from foam and plastic - attached to his helmet may have limited the impact. He collapsed to the ground but got to his feet before being taken from the field. He passed a concussion test and returned to bat.

However, the incident has prompted more debate about neck guards, for Australian coach Justin Langer had even thought they were mandatory.

There had been little research into the use of the guards before Hughes' death but Alex Kountouris, CA's sports science and sports medicine chief, said on Sunday the International Cricket Council, CA, the England and Wales Cricket Board, helmet manufacturers and the British Standards Institution had recently completed a major review.

The development protocols were published by the British Standards Institution in May and are now being implemented by helmet manufacturers.

"Helmet manufacturers did the right thing and came out with products [after Hughes' death]. There was no real knowledge of the mechanism, what exactly they were trying to protect or stuff like that," Kountouris said.

"It was a really good response from the helmet manufacturers ... but since that time we have done a lot of research. We actually have a pretty good understanding of that now. Beforehand, we didn't know the right equipment we were endorsing.

"We have all come to an agreement on what the standard should look like. That also includes the size and the area that needs to be covered ... the sort of force properties it should have and we are also working with other helmet manufacturers who are doing innovative work around neck protectors."

Kountouris said it would take about six months for manufacturers to complete the upgraded product which then would be trialled by players.

"Obviously, at some point, we want to make it a requirement to wear but we want to make sure we have the right products - we haven't seen what the products are at the moment. That's to make sure they are functional and not causing other problems that are unintended," he said.

"When we get to that point, I think we'll be comfortable to say: 'Let's make it a requirement'. There is still a little time to go but we are not far away."

Former Australian captain Michael Clarke embraced StemGuards during the 2015 Ashes campaign after teammate Chris Rogers was struck on the neck. Rogers was already using the guard which is said to have eased the blow.

The response to concussion and head knocks in cricket has improved considerably in recent years, with this Ashes campaign the first Test series to allow concussion substitutes.

"I wouldn't be surprised if they [neck protectors] become mandatory in the future," Langer said after play on day four.

The Australian Cricketers Association did not wish to comment on the use of neck guards, privately declaring it was a matter for the British Standards Institution. But ACA president Greg Dyer praised CA for the manner in which Smith was treated by the team's medical staff.

The former captain was cleared of concussion by team doctor Richard Saw on Saturday after Australian medicos walked him from the field for further assessment in the visitors' medical room.

On a day of intrigue, Smith also required a scan to ease fears that he had fractured his forearm from an earlier Archer bumper.

However, under protocol, Smith required another concussion test before taking to the field for the final day's play on Sunday.