They went to quite a bit of thought about this, recognizing that if you're
driving around with a coating on your car "similar to flypaper or double-sided duct tape" means you'd pick up dirt and bugs as well as pedestrians. So, Google envisions an exterior "eggshell" covering that goes on top of the adhesive layer. This would break instantaneously in the event of a crash, says the patent, "revealing the adhesive layer below, and bonding to the pedestrian."They specify that this eggshell coating will need to fracture into many small pieces to get out of the way.
Preferably, the pieces 232 are of a relatively small size, such as less than an inch in diameter, on average. The smaller pieces 232 help to expose the adhesive layers 220 and 240 so that they come into contact with, and bond to, the pedestrian 270. As shown in FIG. 6B, the back 272 of pedestrian 270 contacts adhesive layer 220 and the pedestrian 270 is thereby adhered to the vehicle during the initial impact.As Dave Barry would say, "I'm not making this up".
In this case, the pedestrian is still getting hit by a car. Now that they're stuck to the hood of the car, how do they get removed without causing more injury? Assume the usual adult weight of 150 to 200 pounds. The adhesive has to prevent that from sliding off, so it has to be strong. How do paramedics rescue the person without ripping them apart pulling them off the car? The words "remove" or "extract" don't show up in the patent (nor do lots of others I could think of for the getting the person off the car) so it doesn't appear Google thought of this at all. Further, what if the pedestrian isn't hit in an overtaking accident like that, but a sideways hit (they're walking toward us, out of the page, in this illustration)? Now they're knees are destroyed from the sideways hit and they're stuck to the car in a horribly painful position.
And what if the person being hit obstructs the driver's vision and now the driver smacks into another car or other obstacle, sandwiching the body on the hood?
There's really no good outcome for the person on the hood. Google, put your effort into preventing that from ever happening.