TFA addresses this.

> The issue isn’t mass alone, but also height. Yes, spreading impact over a greater area reduces the force experienced by any given part of your body, but when that surface area rises further and further from the ground, the impact point on your body rises with it. If you’re hit below your center of mass, you’re likely to fall toward the vehicle. If you’re hit at or above that point, you’re likely to be knocked down in front of of the vehicle instead. The latter becomes less survivable due to the poor visibility offered by taller trucks and SUVs.

> “We see a lot of devastating collisions even at lower speeds because the pedestrian gets punted forward,” said Shawn Harrington, whose company, Forensic Rock, conducted crash testing for the report. “Before the driver knows what’s happened, the pedestrian’s head is under the wheel.”