text: I've edited this on OSM to show the entire "Sandpit" lane as unsurfaced.  I acknowledge this is not wholly accurate but is definitely valid for the  first 180 metres from Emmer Green Rd to where it bends more SE.  See aerial views, or street view. Some routing software currently treats this as suitable for traffic.  
  If you know how to indicate different sections as different surfaces, please do so, thanks.