Horner worried Shield "rushed through" without proper testing

F1's Strategy Group and the F1 Commission decided earlier this year to prioritise development of the Shield concept instead of the original plan for a Halo.

While the Halo was run several times on track last year, the Shield will make its track debut in practice for the British Grand Prix.

The FIA hopes that the Shield can be readied in time for 2018, but if not then the Halo will be introduced instead.

Horner fears, however, that the Shield is being rushed through without all the "due diligence being done properly" and reckons a 2019 introduction would make more sense.

"There are all kinds of issues concerning it," said Horner. "I am not sure it has been through the same amount of testing as the Aeroscreen and Halo did and the catastrophic effect [of big parts hitting it] has to be taken into account.

"So I would rather get the job done properly for 2019 than rushing something through for 2018.

"We will be relying on the feedback from one driver in one set of conditions. It won't be dark, there won't be lights, there won't be loads of oil on it, and those factors.

"I am concerned this is being rushed through without all of the due diligence being done properly." 

Additional reporting by Jonathan Noble