We can see the huge yellow sign and flashing lights, and you can bet that there are several more long before it. There are a lot more stupid people out there than you'd think. Look at it this way, the alternative to the bridge would be a RR Xing, and even if you gated that there would a lot of fatalities.
consider this to be a way that only really penalizes the stupid or their insurance company, and only monetarily. Trains aren't delayed and other cars aren't caught up in their collisions.
There's a railroad trestle in Chattanooga on West 37th Street between Tennessee Ave and Alton Park Blvd. Marked clearance 6'6". They built an apartment complex right next to it. About a dozen U-Haul trucks hit that bridge in a week's time, so they put up signs that say "No U-Haul Trucks" and it still gets hit once or twice a month.
There are, however, a few truckers who list "Network Administrator" on their resumes. Some of us just don't like fluorescent lighting and cubicle farms. Go figure.