I heard about a concussion of two from impacts front and rear. Drivers are complaining. Changes for next year.
Kurt Busch was side lined with a concussion for the rest of the season after a rear 1st crash (backed into a wall) during qualifying at Pokono this year and recently announced he's likely finished with fulltime racing. He will continue on with 23XI team consulting for at least awhile next year. Possibly a few select drives.
In the meantime Bubba Wallace has taken over the #45 in an effort to try to win the "Owner's" championship. While Bubba's away from the 23XI car and in the #45, Ty Gibbs will drive it (23XI) for Bubba.
Alex Bowman was out for several events after backing into the wall at Texas and also sustaining a concussion. So far he's missed three events IIRC, and has now missed the season ending 'play-off' race. He will possibly be back in the seat for the championship final at Phoenix this coming Sunday.
This past Sunday at Martinsville, #8, Tyler Reddick had to pull out of the race due to some type of 'head' issue after a pretty hard 'head-on' into an inside wall after a spin which snapped his head forward then backward very rapidly. He was checked out at the infield care center and cleared. He opted to not get back in the car at that time. He said he still wasn't feeling "quite right".
All three drivers named here and several others through the year claimed they had taken hits in this new car totally unlike any hits they had ever felt before. Note: A good engineer/fabricator can build a car chassis that will take basically any hit you can drive it into with little to no damage ...... the problem is that no live human can tolerate those kinds of forces. Designs have to accomodate some of these forces being dissipated through crumpling of the chassis' before the driver's body has to absorb them.
These next gen cars were built for maximum performance and minimum destruction in a crash. Much like happened with the Whelen Modifieds several years ago when they continued to build the chassis'/cages stiffer and stiffer trying to reduce damage as much as possible in a crash, they finally reached a point where the cars were SO stiff they were resisting crumpling up in a crash and passed all the energy absorption forces to the driver.
Several named drivers were hurt and if memory serves a couple killed before they finally realized what was causing the issue. They've already determined the most serious of the rigid panels that were causing the hard hits with these new cars and have redesigned several support struts in both the front and rear of the new cars.