The Independent Police Complaints Commission will supervise an inquiry into the conduct of officers before a fatal crash on the A413.
Thames Valley Police referred the matter to the IPCC last week after allegations officers could have done more to prevent the March 4 tragedy.
And the commission has ordered them to conduct a investigation, which it will supervise.
Malcolm Tindall, 64, of Aylesbury and Carl Bird, 29, of High Wycombe died when the vehicles they were travelling in crashed.
A woman travelling with Mr Bird also suffered serious injuries.
Just 75 minutes earlier police had been called to the same stretch of road after Martin Kendall, from Aylesbury, skidded into a ditch in his VW Passat.
He says that his car skidded on a 20ft sheet of ice that stretched across the road, and criticised police for not warning other road users about the ice.
Thames Valley Police will be conducting an investigation in to circumstances relating to a collision on the road near Wendover.
An investigation in to the cause of this collision is ongoing.