I left that option open.

A mall parking lot in my area has a speed limit of 17mph. Why not 15? I think it is because it gets ones attention as it is unusual.
The YMCA parking lot has a posted speed limit of 5mph. Its hard to drive this slow, let alone cycle this slow thru it when I go for a swim workout.

I find it harder to keep to low speed limits (20, 15 and below) on my bike that when driving. But I am very careful to keep about ~16mph thru active 15mph school zones while riding in center of lane. I love how it pisses off drivers behind me, sometimes they still honk or agreesively swerve around me. I was almost run over going 7mph in the YMCA parking lot, which is not a short distance having to go all around to back of building.

Al