The Police Investigations and Review Commissioner (PIRC) has found there were failings in police management and response leading up to and following the road accident near Arbroath.
Greig Yorke from Carnoustie, Angus, who served with the Royal Engineers in Bosnia, was involved in a collision with a car on the A92 as he walked home from a night out in Arbroath on June 2.
His left foot and shin were severed in the crash and the 39-year-old owes his life to a female bouncer from Dundee who applied a tourniquet using her ID lanyard at the scene.
Earlier that evening Mr Yorke had spoken to police after being knocked unconscious in a pub and was checked over by medics.
Despite fearing he may have suffered concussion, the father-of-two set out to walk the seven miles home alongside the dual carriageway.
Motorists called 999 after seeing him wandering into the road. At 3am Mr Yorke was involved in an accident with a car near the Salmond's Muir junction.
The ex-serviceman, who has suffered from post traumatic stress disorder since discovering a mass grave in Bosnia, claims the accident could have been avoided and has sought legal advice.
Earlier this year he said: "The police are not a taxi service but whether I was drunk, concussed or both, they have a duty of care not only to me but to other road users."
The report states: "Opportunities were presented to officers and staff to ensure the welfare of the injured party prior to the accident and, had these opportunities been taken, the crash may not have occurred. A number of members of the public expressed concern over the police actions at the scene of the accident."
The independent commission was created this year to undertake probes into the most serious incidents involving the police and scrutinise the way police respond to public complaints.
It interviewed the man and other witnesses, obtained and examined statements from police officers, listened to audio recordings, examined medical and police records and visited the scene.
The report stated there were "clear failings in the police handling, recording and linking of calls prior to the accident".
It added: "The PIRC has recommended to Police Scotland that it should investigate the actions of some of the police officers involved in dealing with the victim, and it should emphasise to its staff that preservation of life by rendering emergency assistance must always be a primary concern of the police."
Commissioner Professor John McNeill said: "Opportunities were presented to police officers and staff to ensure the welfare of the injured party prior to the accident and, had these been taken, the crash may not have occurred."
Superintendent Eleanor Mitchell, of the Professional Standards Department at Police Scotland, said "We will consider the findings carefully and make sure that any concerns are addressed".