I am currently studying Basic Mandarin Chinese by Cornelius C. Kubler and encounered the following sentence in Unit 8 Part 4:
Without 开了 the first part of sentence makes sense to me - the person tells that he/she drove car for a long time. However, the function of 开了 is unclear. Does it describe the duration of driving 半天 or the action 开车 itself? Or maybe it is redundant but helps sentence sound more natural? Is there a kind of construction
verb+object+verb+了 and if so, what are the other use cases?