Research suggests that team cars following riders in the Utrecht time trial at the Tour de France, could save six seconds over the course

The opening time trial of the Tour de France on Saturday could be decided by a team car, not by a rider.

Computer simulations by an expert have revealed how the car can make its rider slice through the air more easily.

And the closer the car gets, the more aerodynamic the rider becomes, even though they are in front of their team vehicle.

>>> Your guide to the 2015 Tour de France in Utrecht (video)

On a short flat stage like the time trial in Utrecht, a team could cut a massive margin from its riders’ times.

Along the 13.8km of the pancake-flat streets of the Dutch city, the saving could be as much as six seconds, says Professor Bert Blocken of Eindhoven University of Technology.

For a stage that will last barely 15 minutes, this is signinficant and could have a big impact on result, even affecting who will wear the yellow jersey the next day.

Blocken used computers to model the air pressure of a cyclist and the team car that follows. Usually there’s a drop in air pressure behind a rider, which holds them back.

But the car behind reduces that pressure drop, making the rider more aerodynamic and having to use less of their energy to push through the air.

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Image of the difference in air pressure when the team car is closer to a rider

And the closer the team car gets to the rider, the bigger the boost.

Officially there should be a gap of at least 10 metres but drivers sometimes get closer. This can happen more easily on straight sections, of which there are several in the prologue.

Blocken, a cycling enthusiast, is asking the UCI to change the rules to make the gap larger – and to enforce them.

“Now there may be an unfair advantage. That 10 metre gap was originally laid down for safety reasons, when this effect wasn’t known,” says the professor.

“To remove any doubts the UCI should now increase the minimum gap to 30 metres, because at that distance the effect of team cars is negligible. And of course that should be strictly enforced, to make sure that everyone sticks to it,” says Blocken.

Your guide to the 2015 Grand Départ in Utrecht