While researching for those images I noticed that I had not read through the entire bicycle section, only pieces.
I am doing so and noticed the equation as well. You failed to take in to account one thing about my draft images: your photos have no scale.
I could not reasonably have made anything other than an approximation.
I was tempted to take my 100' tape measure out to get a propper engineering plot until I remembered that PortlandMaps.org will most likely have all the details plotted out in their maps database.
Also: with all this traffic sign wonkery shouldn't we relocate this line of conversation to an "All about West side" thread?