In a hurry much? (Part 1)

Let's put together a few facts here.  The majority of drivers drive over speed limit, why?  Because they can and consider their chances of being pulled over are next to nil if everyone else around them is driving the same speed.  I'm an engineer and numbers help explain things for me, so let's consider 4 common drivers, who drive at 65 mph, 70 mph, 75 mph, and 80 mph.

If you want to double check my calculations the equation to get time is just distance divided by velocity (Distance/Velocity).  If you want minutes instead of hours just multiply by 60 (min/hr).  I travel about a 30 mile commute to school so those time values would be cut in half.  

So if I were to travel 15 more mph then I would save about 5 minutes of time.  The question to ask, is 5 minutes worth it?  Could I leave 5 minutes earlier and make the time up that way?  The actual calculations show that I would save a few minutes, but here's what I'm thinking.  If I set apart time to leave earlier, say 5 minutes, I will be on time just the same.