Well not for me… 
I’m wondering, how many of you bothered to read this post before posting here?
https://forums.forza.net/turn10_postst131733_-READ-FIRST–FAQ-and-HOW-TO-REPORT-AN-ISSUE.aspx
Okay, so, apparently I have a somewhat similar problem. See when I’m going northbound on the highway in the first Forza game,a piece of the highway will just be gone disappeared and there will be a gargantuan car pile-up and the moment my car enters the Zone it freezes. everything just freezes. The only thing I’m able to do is move the camera and open the main menu. But when I close the main menu or choose one of the options it immediately softlocks the game! and for the record, I could tell it’s a softlock because I could still open the Xbox guide. What in the hell is happening!?
I had the same problem and I managed to solve it. I went through a lot of testing but I can reliably say that my issue is solved now.
There are several things that can affect this, and they can cause the issue by themselves or in combination. You will have to do some work on your part to get rid of this issue if you want to play it on high(er) settings
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The CPU thermal throttling- make sure that your CPU is properly cooled. Make sure your coolers are clean or you won’t be able to avoid thermal throttling, especially during summer. If needed- upgrade your CPU cooler. Laptop owners- buy a cooling pad, it will help you achieve better thermals due to increased airflow and it will make your laptop run more quietly since the fans won’t spin as fast as they would with restricted airflow
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The CPU bottleneck - if your CPU is running too many processes, it will get bogged down running things you don’t use while gaming. Run CCleaner or similar registry cleanup tool and disable any apps that are not essential to be run at startup- it’s better to do it this way or you will have to do it each time you want to play FH4.
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The network bottleneck - If you are downloading something at full speed, it can cause issues with TCP. Torrents can especially knacker your network if you don’t restrict them accordingly. Make sure you limit your upload and download speeds to allow enough bandwidth for your MMOs, I would recommend at least 5Mbps up and down reserved for them
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Wifi bottleneck- self-explanatory, if you don’t have a stable connection with it, get a cable. If your modem/router is on the other side of your house, use power line ethernet adapters
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The disk management tool - This is an odd one, I know, and it took me a while before I noticed the effect it had on my gaming experience. I use Samsung Magician for my 500 Gig Samsung 970 Evo and as soon as I disabled this software, I no longer had the issue with disappearing roads. I’m not saying all disk management tools are to blame since I don’t have access to all of them and I only have one setup, but this is definitely something that is worth looking at
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Audio quality- Another odd one. Some people(like myself) wish to get the best possible audio quality out of their device, so they go to sound settings and select “studio quality” for their playback devices. In short- don’t do that, roll it back to DVD quality and you should be fine. Studio quality audio is very hardware intensive and could cause issues if your rig isn’t powerful enough to handle it(which in most cases- it isn’t)
Since I did this I have been able to play FH4 on (dynamic) Ultra @60FPS with no frame drops, no stutters, no network issues and most importantly- with no disappearing roads
My rig is Lenovo Legion y520
i5-7300hq
16GB DDR4 RAM
1060 MaxQ 6GB
Samsung 970Evo 500GB
Seagate Barracuda 2TB
I hope this solves the issue for you guys, I really do. I have been seeing this issue ever since I got my first car that can reach 400 kph(240mph), but finally- it is reliably gone
Ive got this same issue but on an XBOX One S. Its really annoying me as I cant drive as fast as I need to get anywhere near the top scores on the rivals leaderboards.