Like 67% of the population, the pictures problably slowed you down a bit.  Have you ever tried "Where's Waldo?"

OK. Now suppose that your everyday a) driving speed and b) reaction time to trouble reflect your speed through the letters and numbers on the first test (without the pictures).
 
Then, when the pictures come along in the second test---simulating the distractions encountered in driving (like this neat construction site)---your ability to react, e.g. to a stopped car ahead, is far slower.
 
As you might expect, people differ greatly in how distraction  affects their reaction ability.  In validating WayPoint, we  measured that ability in 6000 drivers and compared it to their  frequency and severity of crashes.  That, in a nutshell, is how WayPoint assesses a person's crash proneness---and does it in just four (4) minutes.