Halo: Is F1's new head-protection system an 'overreaction' or essential?

The controversial 'halo' cockpit head-protection system will be introduced into Formula 1 in 2018

Formula 1 is introducing additional cockpit head protection for drivers in 2018 with the 'halo' - and it is fair to say the decision is a long way from universally popular.

Triple world champion Niki Lauda - a man who knows something about risk having survived a fiery accident at the 1976 German Grand Prix - has called it the "wrong" move.
Lauda, now non-executive chairman of world champions Mercedes, told Germany's Auto Motor und Sport the move is an "overreaction" that has "destroyed" the good work F1 has done by introducing faster and more dramatic cars this year.
Other leading figures - including 1996 world champion Damon Hill - have also said they disagree with the decision, and fans seem generally opposed as well. So why has it happened and what effect will it have on F1?

Why has the halo been introduced?

F1's governing body the FIA is constantly striving to improve safety. While driving a racing car at such high speeds can never be safe, it has become clear in the past decade that the driver's exposed head is the last major risk left unaddressed.
The FIA has been striving to come up with a way to reduce the danger without compromising F1's central ethos as an open-cockpit, open-wheel formula.

During the first practice session at the 2016 Belgian Grand Prix, former Mercedes driver Nico Rosberg set his fastest time with the halo device fitted

The halo - a wishbone-shaped device that has two struts arching forward from behind the driver's shoulders and meeting at a central point in front of the cockpit - emerged over several years of research as the best option.
The original plan was to introduce this for 2017 but at a meeting of team bosses and the FIA in July 2016 it was decided that more development work was needed. But additional frontal protection (AFP) was locked into the rules for 2018.
Over the second half of last season, all teams and all but one driver tried the halo in practice sessions at grands prix and the number who said they felt it was not intrusive far outweighed those who disagreed. Mercedes driver Nico Rosberg even set the fastest time of all in the first session at the Belgian Grand Prix while the device was fitted to his car.
Despite that, concerns remained over the halo's aesthetics and in April this year F1's bosses agreed to prioritise a 'shield' - a transparent front screen - for 2018.
A prototype was tested by Ferrari's Sebastian Vettel in practice at the British Grand Prix but he said it made him dizzy.
It was clear that the work needed to make the shield a success would go beyond the start of 2018, so the FIA decided to confirm the halo.