If a kid jumps in front of your car from 20 feet away while you are going 40 miles per hour (56 feet per second) the 2 objects would collide in about 0.35 seconds.
For comparison a blink is 0.3 to 0.4 seconds.
An unlucky/inattentive human driver may not have time to react at all and collide at full speed.
A lucky/experienced human driver may break hard and swerve out of the way into a randomly chosen lane, left or right, without caring about any cars on either side of him knowing the cosmetic damage to a car can be repaired but a person is much harder to fix.
This driver may not hit the kid nor collide with any other vehicle meaning all obstacles are avoided and no damage was done to anything / person, of course most drivers would be visibly shaken by this event.
The issue is that not everyone has the experience, reaction time and reliability to do this every single time.
A computer driving a car would know the car's exact limits rain or shine along with the current traction on each wheel.
I remember the 2016 GMC Sierra Denali commercial "1000 times a second".
Thus allowing the car to either swerve around the kid completely or maneuver the car into a nearby open lane, being able to monitor each lane and even a complete 360° around the vehicle.
A group of AI powered vehicles could even communicate with each other to help one of them avoid an obstacle.
Say car A and car B are driving side by side on a 2 lane road, 2 one direction a medium and 2 in the opposite direction.
A kid jumps into the path of car A.
Car A asks car B if it is possible to slow down so I can immediately take your position to avoid this obstacle.
Car B says sure and instantly applies its brakes.
Car A then swerves into car B's lane avoiding the kid.
AI may would make for faster trips as well.
Think of a red light.
When the light turns green all the cars don't go at once, they go in sequence.
Car 1 releases his brake and accelerates, car 2 sees the brake lights on car 1 have disappeared and in 0.3 seconds car 2 releases his brakes and pushes the accelerator and this process goes on and on till it gets to your car.
With AI as soon as the light turns green all the AI vehicles could accelerate at a steady rate all at the same time.
Technically the acceleration rate does not have to be steady it just has to be the same for each car so none of them "move" in relation to each other, always 15 feet in front and 15 feet behind for all cars meaning you could have 10 Tesla Model S P100D accelerating a full speed in a line and as long as each one of them maintains the same acceleration everything is fine, although I'm sure some regulatory company will institute a framework, maximum acceleration, maximum speed, minimum space between vehicles and of course all different variables for when it's raining, we still have to obey the laws of physics.