The FIA considered the NHRA style canopy and dismissed it for a very simple reason: F1 cars can land on their tops, which will make it impossible to exit a flip-top canopy, which would be very bad if the car were to catch fire(as Antron Brown can tell you, the canopies do NOT keep flames out of the cockpit any more than the canopies on race boats keep water out).

NHRA top fuels, due to their lack of bodywork on the side, tend to fall off their rollbars onto their sides, making egress simple despite the design.

Easy solution, though, right? Just add doors to the side, like on an LMP, right? Wrong: That weakens the structure of the design. LMPs get around this thanks to their wider cockpits providing more structure. In an F1/Indy car, the narrower cockpits would require dedicated rollstructure to be able to maintain sufficient strength, unless you want to widen the cockpits. And if you have to add the extra roll structure anyway, we must now ask if the canopy is truly necessary.

The answer is no. Small debris is now a non-issue due to the helmet visor strips - a modification that came in the wake of Felipe Massa's accident(which was not the result of the impact in and of itself so much as WHERE it hit - a weak point in the helmet which caused it's protection to fail). These strips have been thoroughly impact tested to prove they are sufficient for small debris, so it's not something the FIA needed to be particularly concerns about.

But if one isn't convinced it's enough, only one simple change is still necessary: Place a section of lexan/plexiglass across the front of the halo. The halo will provide it with sufficient structural rigidity to prevent it from flexing enough for anything small to get past while doing it's job against larger pieces.

I had my doubts about the halo until I saw it on the car and realized that it really is a good idea. It's unique, it will work if it's engineered properly, and the only potential issue with it is fixed by a single minute change.

Moreover, it can be adapted into the current cars with relative ease, as opposed to the canopy which will require a major overhaul of the regulations - something which teams already complaining about costs are NOT going to be keen on dealing with.

And if Kimi is to be believed, there is no visibility issue with the halo. I'm inclined to believe him, given that racecar drivers spend relatively little time looking DIRECTLY ahead, and that the human eye tends to see around objects that narrow rather easily. Take a pencil or pen and hold it at arm's length in front of you, then focus your eyes PAST it. You'll notice it barely impedes your vision at all.