I just finished reading an article in today’s paper that discussed a proposal before the Texas Transportation Commission whereby two interstate highways in West Texas would have their speed limits boosted to 80 mph. Wow. For most of my driving life, that is, since the time I was sixteen, I would have thought that was awesome. But I can tell I am getting old when I start thinking thoughts like, “That’s just too darn fast.”
Reading through the article I could only find two real reasons why this was considered a good idea. Unfortunately, both reasons are flawed:
- “Carlos Lopez, director of traffic operations for the department, said a survey of both interstates found that 85 percent of motorists were driving up to 79 mph.”
- I will definitely be passing that along to our resident statistician as a perfect example of an abuse of statistical data. This statistic really tells you nothing. It looks like an argument that a vast majority are already driving over the current speed limit of 70 so it makes sense to move the speed limit up. Unfortunately, this statistic doesn’t tell you how many people are breaking the current speed limit. Notice how the statistic includes all speeds from 0 up to 79 mph. What if we were to learn that 84.9% of all people were driving up to 70 mph? That is certainly possible under the provided statement. If nothing else, the statement needs to be clarified so as to indicate what percentage of drivers are breaking the current speed limit.
- It also surprises me that 15% of drivers were found to be driving 80 or more. This brings up another good point: Are drivers “consistently” driving that fast or did the survey simply ask if a driver “ever” drove that fast? For example, we might conclude that those 85% of drivers set their cruise control on 79 everytime they hit the interstate, but just as likely, they may “occasionally” drive over the speed limit, and even less frequently, up to 79 mph. In the end, the argument that “Everybody’s doing it” is not only a bad argument but it is not supported by the information provided.
- “It’s generally considered a safer condition when motorists are traveling at a uniform speed,” [Randall] Dillard said.
- Let’s take that what he says is true. Is that independent of the speed at which we travel. For example, it seems that his argument makes perfect sense if the flow of traffic is 60mph and someone comes along and drives 20 mph. There is a lack of safety at that point. It’s simply the principle of relative motion, if two objects are moving in the same direction at different but constant velocities then the difference in their velocities represents their motion relative to each other. On the other hand consider the case where we might raise the speed limit to 150 mph. One car is traveling 150 mph and the other is 140 mph. That would be exactly the same relative velocity as if one were traveling 80 mph and the other 70 mph. And yet there is an obvious difference between the two scenarios. I think the second is much safer than the first simply due to the magnitude of the velocities and not their difference. Thus, Dillard’s idea must have some upper bound. That is, to a certain point it is safer when motorists are traveling at a uniform speed. So the question is whether 80mph is beyond that point. Again maybe I’m getting old, but it seems like it just may be.
The article makes a pretty good set of points in opposition to the proposal citing things like safety and gas mileage as clear drawbacks to the proposal. In fact, I was already planning on posting something with respect to this before I read the article.
I discovered this past week as I was commuting back and forth to Lubbock (a roughly 50 mile one way trip) that if I average 60 mph instead of my usually 73 mph that my gas mileage shot up from 29 mpg to 37.5 mpg. Wow, I say, Wow! 37.5 mpg is wonderful, especially if you consider that I will be making that trip 4 times a week. That is roughly 400 miles per week.
At 29 mpg that would run me about 13.8 gallons per week. At $2.749 a gallon, I’m paying $37.92 in gas a week.
At 37.5 mpg that would run me about 10.67 gallons per week, which comes to $29.32 in gas a week. I’m saving $8.60 a week for 12 weeks. A grand total of $103.20. Not bad. Now the final question is whether Lori thinks that the extra 18 minutes a day (or 14 hours and 24 minutes total for the summer) is worth $103.20.