Passenger trains can either be light on safety or heavy on safety.
A passenger train heavy on safety would put the rails away from pedestrian and vehicular traffic, either elevated or below ground as a subway. A passenger train light on safety would interact as much as possible with traffic. We'll call that type of train, "light rail."
The implementation of light rail can either:
♦ minimize traffic interaction by sometimes elevating, sometimes tunneling, and otherwise walling off and fencing off the train (example: Minneapolis's Hiawatha Line), in an effort to increase safety or
♦ maximize traffic interaction by putting the train on a commercial road like University Avenue (example: St. Paul's Central Corridor project) or the more irrational concept of putting the train on a residential street (example: St. Paul's Gateway Corridor fiasco).
Look over the sample list of light rail accidents (I'll wait.) There are several common themes. The most obvious theme is that light rail trains can't stop. They can't. (If you think they can, reading the previous link will explain why they can't stop.)
The next most important theme is people (pedestrians and drivers) do stupid things. Accident studies have shown the closer people are to their homes, the stupider they get. (Somewhat.) Watch this Houston video compilation.
Imagine a busy intersection with 64,000 cars passing through it daily. Then plop a train running through it. That's what Central Corridor is doing to University Avenue's intersection with Snelling Avenue, Minnesota's busiest intersection.
If light rail existed alone, without traffic or people or transit planners, it would be safe. In a city with urban or suburban traffic, light rail is not safe.
Light Rail Myth #3.5 - "It's a Streetcar"
Light rail is not a streetcar.
It's not a trolley. It's a train.
It has multiple cars. Light rail is longer than a bus. (Like an articulated bus... an accordion bus?)
Is light rail a Streetcar Named Disaster? No, it's not a streetcar.