How to make graph when you have time as a variable

I am trying to make a graph to see where employees time over lap. This data and example show enter and exit time and the duration the truck was at the job. if you could please help me figure this out that would be awesome. I attached the excel file.

sample.xls

Thank you protonLeah. That was really helpful. I have two more questions.

First if I wanted to add more employees time data say for the whole day how do I get the cells to highlight in the right side of the worksheet.( I have reattached the worksheet so you can see what I am talking about )

Second is there anyway just to condense the data down into one bar/ highlighted cell that shows how much time wasn't overlapped. the data represents trucks entering and exiting a job site and I want to see or be able to look at a graph/worksheet and see how many gaps or time there was not any trucks at the job site.

Thank you for all of your help.

overlaps(question).xlsx

Thank you for the help. What formula do you use to have the cells highlight different colors?

Could you take it look at this spreadsheet. I would like to break it down to view the data every minute. I tried to make changes on it but am having a couple difficulties. I mainly want to see total gap time down to the minute. attached is the spreadsheet

see attached