I have a fear of bridges. Not going over them, not looking at them, just going under them. There's that point where I've read the chart 18 times and it says clearly 74' of clearance. I've looked at my boat's 25' mast and calculated 4' of freeboard up to the step. Yes, I should clear. But, when I'm directly under the bridge, looking up, it looks like I'm clearing by 4 inches. I hate that.
This guy (thanks sfsailing list on yahoo) has no fear of bridges.