Complex sentence: Other units were introduced to service as they arrived and completed testing and services checks and were cleared to begin revenue service by the New Zealand Transport Agency; and introduction to the Kapiti Line was achieved in August 2011 when sufficient units became available.
Split into simpler sentences: Other units were introduced to service as they arrived and completed testing and services checks and were cleared by the New Zealand Transport Agency. Introduction to the Kapiti Line was achieved in August 2011 when sufficient units became available.