Hey,

I've reverted this edit.

If there is a single-carriageway in reality, then we map it as such in OSM. 
https://wiki.osm.org/wiki/Dual_carriageway

If access varies by direction, then we use directional keys (like motor_vehicle:forward).
https://wiki.osm.org/wiki/Forward_%26_backward,_left_%26_right

A lot of public transport routes go along here. When we make changes to the map, we need to be sure not to break these routes. To this end, we use appropriate access keys like psv=yes.
https://wiki.osm.org/wiki/Public_service_vehicles

OSM is made for everybody and people use it in many many different ways. When we make edits to the map, we can't tune/hack it to our personal specific needs in a way that renders it unusable to others.