American Brandon McNulty took the overall lead of the Paris-Nice on Tuesday when his UAE Team won the team time-trial as aerodynamic helmets and speeding drones also hit the headlines.

Pre-race favourite Primoz Roglic of Bora dropped 54 seconds on McNulty and perhaps more crucially 30sec on his key rivals Remco Evenepoel of Quick-Step and Egan Bernal of Ineos.

Evenepoel's group were winning by a wide margin of 20sec at the halfway point when the skies opened on them.

"We were outclassing everyone, but the rain began to fall," Evenepoel explained. "And there are corners in the closing part where you can gain five seconds if you go at full speed. So it wasn't our day."

McNulty admitted that his team "got lucky with the weather".

McNulty leads Evenepoel by 18sec in the overall standings and Bernal by 20sec, with Paris-Nice expected to be decided on two mountainous stages in the Nice backcountry at the weekend.

The giant yellow aerodynamic helmet used by Jonas Vingegaard at Italy's Tirreno-Adriatico on Monday was used again at the Paris-Nice on Tuesday by the Dane's Visma team, but cycling's regulator the UCI said it will examine the matter.

"It raises a significant issue concerning the current and wider trend in time trial helmet design, which focuses more on performance than the primary function of a helmet, namely to ensure the safety of the wearer in the event of a fall," read a UCI statement.

Visma came sixth on the day, 38sec from UAE's winning pace in a race where teams of seven riders embarked at four-minute intervals on a 26.9km course around the central French town of Auxerre.

In another first, drones raced alongside the teams at up 65 km/h, zipping along the banks of a section of the Yonne river, offering a far more pacey impression of how fast the peloton actually moves for television viewers.

Wednesday's fourth stage takes in seven hills in a spectacular 183km ride through the Beaujolais wine-growing region.

The last of the climbs stretches 3km with a challenging 7.7 percent average gradient.