The mental picture of this working gave me a laugh.

No. Simply no.
Aside from the obvious technical challenges, simple thought: facing the vehicle during the collision means a faceplant into that sticky substance, probably suffocating the pedestrian to death.
Even if it releases after 10 seconds or whatever, the gloopy glue that filled the nostrils and mouth is enough to block the airways and kill, especially with the panic and shock of the accident.

Adds a new element to the phrase, "there's Klingons on the starboard bow."

What about impact with a deer or other critters? How do you remove a live animal glued on your car hood?

Sounds great, I mean there is no reason at all for adventurous scamps to even consider throwing all manner of objects at the car 'just for fun'!

Where I live it would be about a 100 times more likely to have some mad animal glued to your hood. If it was a deer with a nice rack maybe you could just leave it there as a hood ornament !

Oh my, what a brain worm. I can see contests to see how many pedestrians can be collected before the autonomous car's sensors are sufficiently blocked to prevent continuing. Maybe they should consider simply use spikes. Maybe issue Velcro clothing to everyone, much like David Letterman's suit of Velcro https://www.youtube.com/watch?v=N9uxxqKGmYg

there's an additional problem which hasn't been covered - and i'm claiming prior art over this, thanks: if you see it patented, it was published here first, so bugger off anyone thinking it's ok to patent it - whiplash from being stuck to a bonnet would smash your head into the windscreen MUCH harder than if you were able to slide up the bonnet. so, very simple: this is incredibly dangerous.
the solution: airbags on the front of the car. in fact, if you're going to put airbags on the front of the car, don't bother with the glue at all. just use.... more airbags.
you saw it published here first. publicly. so - no patenting of this idea. prior - published - art. priooorr. aaaaart.

Sounds like this would be more useful to use in amusement park ride, for example, the rollercoaster with no seats. Just glue the person to a sky hook and off you go LOL
Yup bugs, rocks, animals, kids with nothing better to do than bury cars in a parking lot of all sorts of crap, bullies or robbers tossing kids/people on a car hood and then taking advantage of the fact that they can't run away...
What could possibly go wrong? ROTFLMAO

This has to be THE STUPIDEST idea I have ever heard of. So tell me what happens if say the vehicle runs into another car or a wall after collecting a soft, spongy pedestrian on the front bumper?
Can you say ketchup splatter?!?