Raised intersections make vehicles with priority slow down at the conflict point so that the chance of a crash is reduced. Also, if a crash does occur the severity of that crash will be lower as the speed of the impacting vehicle (the bullet vehicle) is lower.  

Here’s an example of the Safe System in action. The driver slows (even though they have priority) giving them enough time to react to the motorcyclist’s mistake.  

Mistakes happen on the roads. Death and serious injury doesn’t need to be the result.