Good old common sense. For the most part it works. It tells us that really hot things are best left untouched, that you shouldn’t jump in front of a fast car, or stepping off a cliff is a bad idea. However for more complicated things, you can’t always trust it.
The reason for the technology that we see around us today is that common sense was rejected centuries ago in favor of the scientific method. The scientific method essentially says that your assertions must be tested first and be repeatable before they’re accepted. It’s the testing that matters, not common sense. In that vein, here are two car misconceptions that seem sensible on the surface but are actually false:
Leaving Your Tailgate Open Improves Your Mileage
This seems to make sense when you imagine air flowing across the top of your pickup and then down into the bed where it meets the vertical surface of your closed tailgate. Surely this must cause more drag when the airflow is forced up and over the closed tailgate. If air actually behaved this way then yes, you’re better off leaving the tailgate down.
But nature behaves differently. The air flowing past the pickup bed splits into two parts: a bubble of slow-moving air that occupies the bed, and a faster moving layer that flows over the bubble and over the raised tailgate. The truck plus the bubble results in a more aerodynamic shape than a truck with its tail gate open.
A 5 Mph Speed Limit Increase Has a Minimal Effect on Road Fatalities
Driving 5 mph faster doesn’t seem like much and it may not increase your individual risk level by much. However, collectively it poses a larger risk. When lots of people are exposed to that risk, even when it’s relatively low, it means that more people will die on the road at the end of the year. When one person flips a coin, his odds of getting a tails up is 50%. But when one million people flip a coin, it’s a near certainty that lots of people will get a tails side up.
The faster you drive, the less reaction time you have because it takes more distance to slow down. That increases the likelihood of striking the bicyclist that pulls in front of you or the pedestrian that isn’t looking your way when he or she crosses the road. It increases the likelihood of your crashing into the driver’s door and into the driver of a car stalled in front of you.
