Here's an excerpt from another wiki page: "Ways that are not marked as cycleway by traffic signs (and are therefore open to non-bicycle traffic (e.g., moped or horse) should typically be tagged as highway=path instead of highway=cycleway, but see duck tagging as well. However, highway=path without any additional information about surface quality, etc... can be hard to interpret for bicycle routers and other data consumers due to the wide variety of path types ranging from perfectly flat and paved ways that simply lack explicit cycleway signs to mountain hiking routes that are completely impassable for bicycles[1]. Adding additional tags such as surface=* makes it easier for data consumers to properly categorize and make use of ways tagged as highway=path." Link: https://wiki.openstreetmap.org/wiki/Tag:highway%3Dcycleway