Interestingly, Light Rail isn't really light. Light refers to its capacity. The train cars are actually heavier than heavy rail. Take a good look at this picture. Then tell us what the probability of a monorail ever colliding with an automobile, truck or school bus is.
Monorails run on an exclusive grade-separated guideway.
The way monorails are designed also make derailments virtually impossible. This is why Monorails have an excellent safety record.