I've discovered a flaw in the game that lets you basically kill as many people as you want and blow up endless amounts of cars with very little risk of getting killed. Basically you just have to jump on top of a building that is otherwise not accessible by foot or ladder first. You can use cyberware leg implants or jump on a dumpster or a vehicle or whatever to get on top of the roof, then stock up your ammo in the crafting menu and go on a mass killing rampage.

This will get an arrest warrant issued, but just duck out of sight on the rooftop, or shoot the cop(s) that show up as they're super easy to kill. Drones do not usually show up but if they do they stay at street level and are easy to kill. The game's cop AI is not smart enough to handle the situation of you being on the roof, it just doesn't know what to do, and once you defeat the first cops that show up, it doesn't send any more cops after that.

Surprise caveat: If you kill enough people and get enough badges after you while doing this beware, the game MAY auto-spawn machine gun turrets on the sides of buildings, overpasses or other structures even though there were no turrets there before. Be on the lookout for them with health MK3 packs just in case. If you shoot the turret out it will not respawn. It seems there are only a fixed number of turret spawn locations so you shouldn't likely see more than 1-2 or so turrets pop up if you get any at all.

The threat of cops and turrets is so low that they are easy to take out and then never return and you can mow down countless people just for fun. What's even more interesting is that if you blow up cars that are coming towards you they will blow up and stop motionless as expected, but... if you blow up a car that is driving away from you even after the car has blown up and has no more wheels and is completely destroyed, the driver will continue to drive the now burnt out car around the city as if the car was perfectly fine, racing off in flames with no wheels.

It is epic fail, epic bad game programming, but epic laughs of destruction at the same time. See how many pedestrians you can litter the pavement with while you're up there.

You're welcome.

Hmm, don't think I found a garage with a secret code or a hole in an overpass yet. Got map pointers?

Update: Or do you mean hole in overpass due to game bug with graphics making the highway disappear, as I've had that happen reproducibly near Building 10 near the roof of the parking garage.

This was screenshot I took of it
here's another.

Ah, never seen that one yet but might not have stood in the same place yet. The one that I get all of the time is if you go into V's parking garage at Building 10 in her primary residence, then walk (or drive) up to the top floor of the parking garage there is an exit ramp onto the freeway. Turn left and travel just past Building 10. Try to jump on the rooftops around there (save the game first!) and at some point in time the game engine flakes out and a big portion of the freeway and other things just disappear completely. Sometimes distant (or even close) buildings completely or partially disappear and parts of the game are floating in the air. If you try to walk over the missing road it responds like the road is still there but just invisible.

Save+exit+reload makes the road appear again but it doesn't take very long until it randomly disappears again. The graphics in the screenshots you provided are very similar in nature where textures just randomly disappear from the road/buildings or other items, or they flicker on and off.

Next time I'm near city center I'll see if I can repro yours.