Gloucester Bus Station new layout

In general OSM only allows one view of the data, which should be as close to what is currently on the ground as mapping contributions allow. Therefore the current active layout should be retained.

Many changes can be mapped using the construction tag in association with landuse and highway, e.g., construction=service and highway=construction. This allows the new configuration to be mapped quickly once it goes live.

If you want to map the new configuration for your own purposes than you could do that off-line using the JOSM desktop editor. Potentially such mapping could be merged with the main database when the new bus station opens.

In general there is considerable experience within OSM of tracking changes to public transport infrastructure so as to show the new facilities from day one (notably with new tram and metro lines). So there are people who can provide very specific advice.

I'm presuming this is Gloucester, England on the basis of this article, and your edits(!). I also presume that the shops at Grovsenor House have gone (at least in part), and that, because the new building overlaps, the building itself is (partially) demolished). So my minium recommendations would be:

• Delineate the current construction area with landuse=construction
• Remove or (better) change the tagging of any demolished buildings (e.g. change building to demolished:building). The latter is better because it shows to other mappers that the building is gone. It is not unknown for people to assume more up-to-date data is actually older than the aerial images.
• Mark any access footways which are currently obstructed as access=private.
• Some new information can be added, for instance location of new bus stops, but use the highway=construction, construction=bus_stop approach.

HTH