Yesterday, I was heading from my office in Beverly, MA, to a meeting in Canton, MA. According to Google Maps, that’s a distance of 49.3 miles, almost all of which (43.0 miles, or 87%) is on Route 128 - a four to eight-lane highway. Google estimates that it will take me exactly one hour to make that drive, which, conveniently enough, indicates an average speed of 49.3 miles per hour.
So, to get to my meeting on time (8:30 am), what time should I leave? Given that the speed limit on Rt 128 is 55 mph, and I have to travel right in the middle of rush hour, that one hour estimate seems a bit optimistic, but I will certainly take it into account. The smart thing would be to assume that I won’t be able to average more than 25 mph, and allow two hours for the drive. If I get there an hour early, I’ll grab a cup of coffee and catch up on my RSS feeds. But here’s where things start to go wrong. There’s that little part of my brain, the “rational” part, that says “it couldn’t possibly take twice as long as the Google estimate, could it?” I mean, there’s realism, and then there’s going over the top.
So, I decide to leave a little before 7:00 am - giving myself plenty of time to get there - after all, I added 50% to the original estimate. I’m sure you can guess the end of the story, especially if you live in the Greater Boston area: I arrive about 20 minutes late.
Any of this sound familiar? We humans have a tendency to be over optimistic when it comes to time estimation. And time is such a scarce resource in our culture that we don’t want to give the impression that we have any of it to spare. And so, we submit our hopelessly optimistic software delivery estimates, and as the deadline approaches, we start to cut corners, and that is where quality suffers.
Fortunately, I have never been involved in a serious car accident. But it seems likely to me that, if it were ever to happen, it would be when I was running late to get somewhere.