Head-on Collision Survival Chances in Furious 7

At the speeds with which they were travelling, and no restraints, they both would have been ejected through the front windshield, or at least been slammed into the wheel/dashboard.

Imagine getting hit in the chest with a bowling ball fired at a speed of 25MPH. If you didn't break a rib, you would certainly have the wind knocked out of you or sustained some sort of bruise to your torso. Now imagine that bowling ball hitting your head.

There are always cases of "freak" accidents or survival incidents, but those are far from the norm and likely represent miniscule fractions of a single percent occurrence rate.

While I can't find solid data on head-on collisions and speeds which are fatal, I did find this blurb about rear-end accidents and potential for whiplash:

The acceleration-deceleration forces which cause whiplash injury are sufficient to permanently disable you. Even in a low speed rear impact collision of 8 mph, your head moves roughly 18 inches, at a force as great as 7 G’s in less than a quarter of a second.­¹

So, even at the very least, it's unlikely that an unsecured driver could walk away from a deceleration of 7 G's with no damage whatsoever.

¹ NeoruSurgeon.com

Yes, it's likely for someone to walk away from a low speed crash. Assuming 25~35 MPH total, even a pedestrian to car hit, there's a significant possibility of walking away unharmed.

State of Florida. In Florida in 1993 - 1996, 32,651 of the pedestrians in crashes were in single-vehicle crashes (91 percent). For 23,831 of those pedestrians (74 percent), estimated travel speeds were provided for the striking vehicles. For those pedestrians, there were 1,550 (6 percent) fatalities, 6,414 (27 percent) with A (incapacitating) injuries, 9,206 (39 percent) with B (non-incapacitating) injuries, and 6,583 (28 percent) with C (possible) or no injuries. The proportion of serious injuries and fatalities increased steadily with increasing vehicle speeds (as estimated by the investigating police officer). The distribution is shown in Table 2 (Table 5 from the main report).

The above stats show a 23% chance of a pedestrian surviving a 25 MPH hit with minor scrapes or less. At 35 MPH it drops to 16.6%.

But they are clearly going much faster.

Looks like they shift into 3rd Gear. That's roughly 40 to 60 MPH range. And the distance is quite short. They gun it. Those cars can do 0-60 in how many seconds? So we can assume each is going 45 MPH. Because speed is relative, hitting a wall when you are going at 45 MPH is the same as a wall going 45 MPH hitting you standing still. If you are both moving towards each other, it's cumulative.

So both of them are experiencing a 90 MPH crash, with no seat belt, no air bags, nothing but the crumple zone of their car. The chance they BOTH walk away from that is so remote that it can be considered 0%.

This report on Wrong-Way crashes on divided highways (82% are considered head-on, with at least one car at highway speeds) reports that 22% are fatal. That's with airbags and seat belts and other mitigating circumstances.

So, in short, enjoy your popcorn.