easy.
Interstates were built to not have intersections like Railroads.
What makes trains unsafe is that they have to cross roads. That is not an issue with the interstates.
Uh, no. What makes trains unsafe is that they are trains ... which means that -- like everything else in life -- they never have a 0% failure rate.
It's really that simple.
Here's a perfect case in point ...
Don't take the exact numbers here at face value, but I read somewhere that the average person in the U.S. who gets a driver's license at the age of 17 and drives for 60 years will depress a brake pedal three million times while driving forward, and will get in three motor vehicle crashes that would have been prevented if the brakes were applied correctly. That's a "failure rate" of one in a million, or 0.0001%. Can you think of any automated product that operates this efficiently?