Lotto-Soudal's Greipel sprinted clear for his second victory of the race and his 18th stage win overall at the Australian Tour, the first race in this year's International Cycling Union World Tour. 

It came in a 90 kilometres criterium consisting of 20 laps of a city centre circuit in Adelaide.

Greipel burst clear to cross first in a time of 2 hours 01min 19sec.

Australia's Mitchelton-Scott rider Caleb Ewan came second and Slovakia and Bora-Hansgrohe's world champion Peter Sagan third.

Both riders were awarded the same time as the leader.

South Africa's Impey, also a Mitchelton-Scott rider, finished safely in the peloton to win his first general classification event in more than three years since the 2014 Tour of Alberta.

He won courtesy of count-back because of second-placed finishes on stages two and four after clocking the same overall time as BMC Racing's home star Richie Porte.

"Thrilled… sometimes the stars line up and everything goes well and according to plan," Impey told Channel 9 afterwards.

The Netherlands and Dimension Data's Tom-Jelte Slagter finished third overall, 16 seconds behind the leading duo.