Brian Williammee writes:
Sure, we'd save some gas if everyone drove 55. But every 100 miles driven at 55 instead of 75 means another 29 minutes on the road. That time has a real cost- decreased productivity, leading to lower national income, and thus lower person income surplus and lower tax revenue, all resulting in less money available to work on things like renewable energy or to purchase marginally more expensive and more eco-friendly products.
If that extra time isn't spent on work, then it's taken out of leisure time, something many people are sorely lacking to begin with, which itself contributes to lost productivity based on mental health issues and general stress.
If you really want to prove that your thesis would improve the environment, you ought to conduct a complete cost-benefit analysis including these factors, rather than pointing to a single chart and referring ambiguously to lots of "studies."
Furthermore, fuel economy for a GTI is not at all representative of the broader spectrum of optimal speeds for gas mileage on different vehicles. A 2002 corvette with a manual transmission gets about 2 mpg *more* at 75 than 55, due to a low-geared 6th speed. This affect may be observed on any car, whether exotic or economy oriented, that has a low-ratio top gear and a low coefficient of aerodynamic drag. Nevermind that the chart is either misleading or incorrect- any chart that states a GTI can get 90 mpg at any speed (the blue line in the graph at 35 mph) needs a reality check.
I like that you want to save the earth. I'm all for it, especially given that I don't see overt calls on your site to re-legislate the national 55 mph speed limit. But please don't go about attempting a green existence with your eyes closed.
Our reply:
 The Missouri Department of Transportation is starting variable speed limits along I-270. When congestion starts building along stretches of I-270, MoDOT will use changeable speed limit signs to vary the speed limit on the road. Speed limits along I-270 could range from 60 mph during extremely light traffic, to as low as 40 mph during extreme congestion. This would also include congestion due to crashes along I-270.
Your interest in the overall pace of traffic is important. In fact, it turns out this is the best argument FOR speed limits that are even lower - to reduce congestion! This important point is counter intuitive so please consider this metaphor from the Missouri DOT website;
"If traffic slows down as they approach a congested area and all the
drivers stay at a constant speed, traffic will get through the
congested area faster. Imagine the highway as a funnel. Now, imagine
the traffic which has to travel along the highway during a certain time
as a container of rice. If you pour all the rice into the funnel at the
same time, it gets congested at the bottom of the funnel and takes some
time to work through the funnel. Now, if you slowly pour the rice into
the funnel – keeping it at a steady pace – the rice moves through the
funnel evenly and doesn’t cause congestion. In fact, even though the
rice is entering the funnel slower, all the rice gets through the
funnel (to its destination) faster.
Note: this metaphor is based on an
idea from Paul Haase of Sammamish, Washington, in response to a
challenge by Washington State Department of Transportation Secretary
Doug MacDonald."
Most drivers are not out on lonely desert highways where your analogy would apply - most drivers are on busy local roads and commute about 30 miles (48 km) to work each day. Please take a look at the chart below.
|
Miles (km) to travel >
|
10 (16km)
|
15 (24km)
|
20 (32km)
|
25 (40km)
|
30 (48km)
|
35 (56km)
|
40 (64km)
|
45 (72km)
|
50 (80km)
|
55 (88km)
|
60 (95km)
|
| Minutes @ 55 MPH (88km) |
11
|
16
|
22
|
27
|
33
|
38
|
44
|
49
|
55
|
60
|
65
|
|
Minutes @ 65 MPH (104km)
|
9
|
14
|
18
|
23
|
28
|
32
|
37
|
42
|
46
|
51
|
55
|
|
Savings (minutes)
|
1.68
|
2.52
|
3.36
|
4.20
|
5.03
|
5.87
|
6.71
|
7.55
|
8.39
|
9.23
|
10.0
|
For many drivers it will only take a few extra minutes and the reduction in stress, fewer colliosions and big energy savings are well worth it, so please, if you see one of us observing the speed limit, please don't ride our bumper and flick your high beams or get annoyed and have road rage. The purpose of the bumper stickers is to let you know we are taking it easy, enjoying the journey, OK? I hope you will respect our right to observe the posted speed LIMIT, and recognize that on most urban highways it is often 55 MPH already, though rarely regarded and almost never enforced.
As concerns your Corvette getting better MPG at 75 than 55 MPH, please, download this free form and document this miraculous violation of the laws of physics .
Please also review these related articles examining this in further detail:
Time Value vs. Speed
Independent truckers earn more @ 55 MPH
Are We Really Serious About Saving Money On Gas?
Take care,
Tim
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