Working on a construction company, you need to know how to operate the heavy equipment if you want to be a valuable part of the company. Otherwise, you would end up dispensable since they can easily find someone else to do the job. Of course, engineers are indispensable since they got the brains for the job and if you are don't have the proof to show that you have the brains then you are dispensable for the company and there won't be any guarantee that they would hire you again. Then again, if you can drive most of the big equipment of the company then they can't fire you easily.
In this game, there would be no job better than the driver since you are operating most of the machines. Don't look for something to do either if you are an engineer since you won't find something like that to do in this game. The idea here is to complete all the necessary task of the driver and operate most of the machines that you can find in a construction site. Don't worry about the timer too much since it won't affect the game much. But, you do need to complete the job in order.