From OpenStreetMap Wiki
|route = tram|
|The route of a tram service|
|Used on these elements|
|Status: in use|
|Tools for this tag|
This tag can be used to mark the route of a tram service (eg the "Red line").
How to tag a tram route relation ?
Use one relation for each direction, so you need 2 relations for a tram line.
|ref||reference||The reference by which the route is known. e.g. 4, 4A, X13, etc. (recommended)|
|operator||operator||Name of the company that operates the route.|
|name||individual name||The name of the route or line.|
|network||local / regional network||Name (abbr.) of the network; e.g., BVG, RMV. (optional)|
|wheelchair||yes / no / limited||Indicates if the trams on the route are low-floor trams for wheelchairs. (optional)|
|colour||ex: red / #FFEEDD||The "official" color for the tram route. Identifiers in some cities. (optional)|