• Kipchoge will run 4.4 laps of a 9.6 kilometre course, consisting of a long straight with a loop at each end.
Eliud Kipchoge was greeted with a misty autumnal morning and a smattering of fans on Saturday for his bid to run an unofficial sub-two hour marathon.
The marathon world record holder's highly controlled attempt to break the two-hour barrier was due to start at 8:15 a.m. local time (0615 GMT) and organisers were hoping for a crowd of up to 8,000 in Vienna's Prater Park.
Kipchoge will run 4.4 laps of a 9.6 kilometre course, consisting of a long straight with a loop at each end.
The sport's governing body, the IAAF, will not recognise the run as an official record because it is not in open competition and it uses in and out pacemakers.
Kipchoge, 34, the reigning Olympic champion who set an official world record of 2:01.39 at the Berlin marathon in September last year, missed out by 26 seconds when he previously attempted to break the two-hour barrier in Monza in May 2017, a race run without spectators.
The 34-year-old will be supported by 41 pacemakers who will run in rotating groups and will form a V shape around Kipchoge - as opposed to a diamond formation in Monza - to try and protect him from the wind.
They will also follow an electric pace car that has been programmed to complete the course in 1:59.50 to ensure that Kipchoge runs a steady pace.