Originally Posted by
FBinNY
I agree that the design speed is very low, but it might be appropriate, depending on the intended purpose of the path. While most experienced riders ride faster than that, I believe that the realistic average is nearer 12-13 mph than some of the figures you stated.
Safety standards aren't usually designed around the average speed, but the 85th percentile -- designing a facility for the average makes it unsuitable for half the intended users. Designing for the 85th percentile leaves it unsafe for only 15% of users.
Where you need to encourage slower speeds because of other constraints, you should do that with safe traffic calming designs, not simply making it dangerous for users to go their usual speed.
That's especially true when you're dealing with vulnerable user groups like children or the elderly. You want fast riders to slow down, but you also want them to have excellent sight lines to see children ahead of them on the path. King County, which surrounds Seattle, insists on maintaining 20 mph sight lines and stopping distances even when the posted speed limit is 10 mph, because they recognize those faster riders won't all slow down, and shortening sight lines just increases risk for vulnerable users.