“Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has.” ~ Margaret Mead

Friday, March 18, 2011

Brad's Thoughts on Driving to Save Energy

Driving to work tonight, I thought about the difference between driving for myself, versus driving for the community.  I mean, I have a few thing to fix on the '95 Toyota pickup I bought last month, but on a business trip last week I got 29.9 mpg, the tank full before that was 23 or a little better.  I know from experience that with this vehicle, my best mileage is at 65-70, where the Lincoln Town Car I drove before (until it fell apart on the road) topped out at 45 mph - at 22 mpg.

I don't accelerate harshly, unless there is actual hazard or danger (much like my approach to yelling at livestock or kids).

1) I lived a couple winters in Minneapolis.  They advised there not to let the engine idle to warm up - after a few seconds, put it in gear, and drive, being very gentle on the accelerator until the engine warms, and let the engine work at above-idle speeds to warm up.  They contended it was less stressful on the engine and transmission (since you are being gentle on the transmission as well).

2) An uncle told me most accidents in intersections happen the first three seconds after the light changes.  So I don't enter then - and I don't try to 'beat' the yellow light.

- this has a community effect. People entering late in the yellow cycle may not be through the intersection when others get the green light - so 1, or 2 - or 40 cars wait an extra 3 to 5 seconds, because of one driver out to 'beat' the lights.

3) Another uncle was in the Army, and while showing my Father and me around Fort Hood, TX, someone came up behind - closely.  Uncle Robert claimed that if a tailgater is going to hit you, you are safer going at a slower speed - so gently slowing down does a couple of things.  First, it makes any ensuing accident lower energy, and hopefully more survivable.  Second, it makes it easier for the tailgater to pass.  I know the last thing I want behind me is someone anxiously breaking the law (tailgating), and getting angrier and more frustrated - and more daring - all the time.  Let the wiseacre behind go look for the speed trap.

- I am not sure there is an energy component to this one.  I do know that speeding up is usually the wrong thing to do - it encourages the odd wiseacre to 'push' you harder, to see how much you can be pushed.  On a family vacation one such driver passed and harassed Dad several times over several miles. 

- I am *not* advocating a sudden slow down - nothing abrupt, merely an easing back one mph every minute or so.

- I have had people pull too close - and when I stayed at my speed or started slowing, gradually - back off.  If they back off to a safe distance I speed back up to my chosen speed or the speed limit, whatever.  But some people maintain that longer distance back.  And that does save energy.  There is a *lot* of acceleration in following a vehicle at a close distance, a *lot* of small accelerations.  And that means their mileage improved by leaving that larger distance.

4) While commuting to work in St. Louis some years back, on four-lanes-each-way Interstate, I chose to not be an aggressive driver.  I decided to always leave enough room in front of me for two cars to pull in.  There were a couple of reasons - it gave me more time to react to the drivers ahead of and beside me, and reduced the risk that someone wanting to change lanes might attempt something desperate.

- Leaving more room in front of me doesn't do me a lot of good - or harm - time wise, but it does reduce some of my need for reactive acceleration - thus is a slight benefit, mileage wise.

- But that slight benefit, mileage wise, gets passed back to the cars behind me.  I am reasonably convinced that if everyone maintained the legal safe following distance ahead of them, both while driving in their lane and also when changing lanes - there could be no stop-and-go traffic jams.  If I recall correctly, safe distance, legally, is 200 ft between vehicles when the posted limit is 45 mph or higher, 100 ft for lower posted speed - regardless of the speed being traveled at the moment.

- Recall the comment about about the acceleration needed for following closely.  Not every vehicle, nor driver, will accelerate identically to the driver ahead.  So everyone behind a driver that falls behind the driver ahead falls behind a bit further; none of them can make up more speed or time than the vehicle ahead of them.  The 'flinch' - any time a driver slows - gets passed back to every successive close-following vehicle.  Vehicles with longer following distances - can ignore lots of small changes without affecting the cars behind him.

- So I contend that leaving that larger gap in front of me - not slowing down, just leaving that gap - benefits time wise and fuel wise, the cars behind me.

- My own experience, and observation of tailgaters, is that that longer following distance? It decreases the stress on the driver.

That is my suggestion for a 'small change' that might benefit the community.  And maybe decrease by one the number of energy and time wasteful accidents.


You can read more on Brad's thoughts at his blog Brad's Take where he writes about ideas on draft horses, Peak Oil, conservation, and low tech living. 

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