On the average
For any average, the “average” may not be the most-occurring data, as averages include extremes. For example, an average temperature for a given date may be 70 degrees. But historically, that average could be derived from 40% of 65 degree days, 40% of 75 degree days and only 20% of previous days recording 70 degrees.
Such was the theory at play during my drive to Seattle and back this week. Attempting to maintain a steady speed of 72 miles per hour (according to my speedometer — a topic addressed in a bit), I found most vehicles to be travelling at speeds either greater or lower than mine.
So the average speed for that day may have been around 72 mph, but seemingly half of the prevailing traffic was either going faster or slower—like 60 or 80 mph. This was evident, since I could never “rest” in the right hand lane at my steady speed for more than a moment without coming upon a slower vehicle. And as I made my moves to the left lane to accomplish the subsequent passes, I was regularly thwarted or delayed by an approaching vehicle going much faster than I was — or was dictated by the 70 mph posted limit.
I know that differential of speed on the highway leads to conflict and contact. One of the many examples of how accidents result is when the speeder is travelling faster than the majority of traffic (like 90 mph). Such drivers require all lanes to weave their paths through traffic. As a consequence, the speeder might occupy right hand lane at the same moment another driver is returning to that lane from the left, not expecting the speeder to suddenly appear there.
No matter how I timed it that day, I generally had to cut my cruise control off momentarily as I approached slower traffic to accommodate the speeders without detaining or riling them. Often, even when I did move to an open left lane to pass, I eventually experienced a tailgating speeder before I finished the pass.
What’s the reason for this drastic speed variance? I think it’s simply drivers’ whims to speed or not — that is if they are aware of their speed — and I believe many are not. For both fast and slow drivers, I think many are oblivious of their given speed. This is evidenced by the varying speeds I witnessed by the same vehicle during my trip. One moment I would pass a white pickup while I traveled at 72 mph, then it would go by me at 80-85 mph and shortly thereafter I’d be passing the same truck again, all while holding my same speed.
Now, as foreshadowed, something about speedometer error. As stated, I drove at 72 mph — that’s because I determined my speedometer reads about 2 mph high at 60 mph. Virtually every vehicle has a degree of error, usually on the conservative side in a new vehicle, but variance happens due to tire wear, custom tire/wheels, gearing changes or faulty sensors.
I check my timing (with stopwatch or passenger’s watch with secondhand) past several mileposts at a steady indicated 60 mph to determine speedo accuracy. It pays to know exactly how fast you are going in spite of what may be indicated.
If everyone were driving at a speed near the 70 mph posted limit, traffic would flow more smoothly.
Readers may contact Bill Love via e-mail at precisiondriving@spokesman.com.
