A trend I’m seeing more often is agencies whose high-speed arterial roadway design standard calls for the construction of a sidewalk on one side of the road and a path on the other side. The photo below is one such roadway, with a concrete sidewalk on the west side of the road (probably 5′-6′ wide) and an asphalt path on the east side of the road (probably 8′ wide). For the purposes of this discussion, we can assume that the only difference between sidewalks and paths is the width (6′ vs. 8′), and the materials they’re made out of (concrete vs. asphalt). The path is intended primarily for bikes (although it’s a shared-use path), and the sidewalk is intended primarily for pedestrians.
In most situations, this situation is not optimal because it requires cyclists and pedestrians to sort themselves onto opposite sides of the roadway. In practice, this doesn’t really happen. Cyclists and pedestrians tend to just use whichever facility happens to be more convenient. For example, in the photo above, if your trip origin and destination are both on the west side of the corridor, you’d have to cross the busy roadway twice to bike on the path rather than the sidewalk. Most people would just bike on the sidewalk, especially in cases where they are unlikely to encounter a pedestrian.
Paths work just as well as sidewalks for pedestrians in this context, but sidewalks don’t always do a great job for bikes. The extra 2′ of width and smoother ride of asphalt goes a long way to making cyclists feel more comfortable. The biggest benefit of an 8′ path over a 6′ sidewalk is that it allows users (bikes or peds) going in opposite directions to safely pass each other.
In these situations, I usually recommend that the client construct shared-use paths on both sides of the roadway. From a cost standpoint, it’s usually about a wash (if anything, the path tends to be a bit cheaper than the sidewalk). The path requires 2′ of additional width than the sidewalk, but (as in the photo shown above) space is often not a large constraint.