There is an unpaved track which runs parallel to Ambillawatte Road for about 70-80 metres and then does a 90 degree turn to run parallel to 20th Lane, starting from the map marker.
This track is visible on satellite view, and has 10-15 vehicles traveling on a daily basis - from the residences at the end of the track, and also from a welding and grill work business.

This used to be on OSM at one point, but was removed. Access from the residences/businesses to the main road is via Pirivena Road