The topic of elastic collisions and inelastic collisions is covered in your typical physics textbook. To react or over-react is on a case by case basis. I was riding my bicycle home from school one day and was pushed off the road (hit) by a loaded concrete mixing truck who didn't even feel the nudge. I later smacked the side of a school bus pulling out from the loading area at my second high school, same bicycle. No damage to the heavier vehicle because of my relatively low mass and angle of impact. My bicycle and I suffered little, again because of angle and elastic collision. The mixer driver kept on going, the bus driver was horrified.

Metal and people both bend and distort during collisions. The unfortunate parts for the people are unfortunate. I've been lucky to have had well built vehicles in subsequent collisions. Have I been statistically safe? Probably not, just lucky. Remember, too, that I work around heavy equipment where speed and mass will kill me dead if I'm hit, and the cleanest flat blade shovel may not get all the pieces.

In this photo, the Caterpillar 657E scraper is traveling down a 15% grade at about 45 mph, loaded to approximately 150,000 pounds with rocky soil, and unable to stop for approximately 500 feet. When nearly stopped, the operator performed a u-turn before returning to the cut area. The contractor operated 22 of these machines without incident during the project. However, my geotech opposite accidentally ran over and crushed my Ohaus field scale (an approximate $700 loss for the company I worked for) on the same day as the photo. Note the flying sand off the tire as the scarper 'flew' by me.