Less safe than what the test should have been with one simple change.
The IIHS 40% 40 MPH moderate overlap crash test in to a fixed barrier uses a deformable barrier in front of the fixed barrier. This barrier absorbs some energy, so the test is actually less severe than 40MPH in to a fixed barrier. I don’t know how much less. But I do know that the amount of energy absorbed by that deformable barrier is more in relation to the test vehicle for small vehicles than large ones, giving small vehicles an advantage. This means that heavy vehicles such as trucks and SUVs actually have to be built stronger in front in proportion to the vehicle weight, or be longer in front to lengthen the crash pulse, compared to smaller vehicles to achieve the same result. Light weight vehicles can rely on the barrier absorbing more energy. So the result is the opposite of what the desired result should be. The size mismatch of vehicles on the road is bad enough without compounding the problem by having the heavier vehicles proportionally stronger for frontal crashes.
How it should have been is heavy vehicles should be weaker in front since they will more likely crash in to lighter vehicle, and small vehicles need to be stronger or longer in front since they will likely hit a heavier vehicle. This could have easily been done by using a heavy movable barrier, such as a 10,000 pound block on wheels with no deformable barrier in front. Heavier vehicles would cause the movable barrier to roll back faster, allowing them to get by with a front end that’s a bit weaker.
It’s entirely reasonable for lighter vehicles to get lower crash test scores, and pressure from the industry should be ignored. This is an honest rear world representation.