From OpenStreetMap Wiki
|Cycle lanes or tracks provided within the carriageway or next to it, the same in both directions.|
|Used on these elements|
|Status: in use|
|Tools for this tag|
This tag is using the same values as cycleway=*, cycleway:left=*, cycleway:right=*. It explicitly documents that value applies to both directions and is used instead of tagging cycleway:left=* and cycleway:right=* with the same value.