Tuesday, January 31, 2017

Live Work Commute 3

Get to Work!

(Disclaimer: I am presenting data here to provide a common framework of discussion about commuting without expressing any opinion of my own.)

Summary:  With the most optimistic assumptions, we can eliminate at most 1.3% of GHG emissions by getting 10% of the US population to abandon cars completely.  More likely is about 0.5% reduction in GHGs by getting 10% to go to car-less commutes.  The reason is that of GHGs, only 26% is due to transportation.  Of that, only half is due to personal vehicles (the rest is trucks, planes, etc.).  Of those personal vehicles, only one quarter to one third of use is for commuting.  So 10% of 33% of 50% of 26% is 0.5% of GHG emissions reduced by biking to work.

That is for the wildly optimistic assumption of 10% bike commuting.  Actually, it is about 1% for the SF Bay Area and less than 1% for the country as a whole.  That means between 0.05% to 0.15% of GHG reduction by biking to work.

There are many excellent reasons to bike, or walk to work (health, mental reflection, appreciation of the environment) as described very well here:
However, as a way to save on GHG emissions, walking/biking to work is not significant.


Data:  In the SF Bay Area only a little over 1% bike to work   That number has gone up and down but stayed around 1% over the last few decades.  Sunnyvale is not significantly different.  Here is the census data (click on image to enlarge):
Other states and cities in the US aren't much different (click on image to enlarge):
Major urban areas max out at 6% biking to work and 15% walk to work.  Most are far below that (click on table to enlarge).


For all the fans of Portland (which includes me) I have to add that the 6.1% biking to work (above) is only within Portland City boundaries (pop. 630,000).  The entire Portland metro area of 2.4M has 2.6% biking to work.  C.f.,

Nationwide, we use cars.  (click on image to enlarge)
Vehicle ownership seems to have peaked in the last 15 years:

Commuting is between a quarter and a third of all personal car use.  Getting people out of their cars for commuting is not even close to adequate for serious GHG reduction.  We also need them biking to the store, when visiting friends, and for recreation.  This is possible in that it doesn't violate any laws of physics so let's assume that everyone who bikes to work also bikes to everything else, too. (click on image to enlarge)
Of commute distances, about 50% are within 10 miles of home which is probably the outer limit for most people to commute by bicycle. (click on image to enlarge)
So what about Green House Gas emissions?  Transport (including ships, planes, freight trucks) is about 26% of the total. (click on image to enlarge)


Of the 26% of GHGs originating from transportation, light-duty vehicles (cars, SUVs, pickup trucks) are 63%.   (click on image to enlarge)
We have to allow that some of the light duty trucks are actually used for work so Joe the Plumber has to "commute" to work in his truck.  At most, maybe 50% of Transport GHGs are from people commuting by car but who might be able to bike or take buses.  If we got 10% of those people currently commuting by car to bike, we'd be doing very well indeed.

Now the final calculation.  
  • Max bikers = 10% of personal vehicle GHGs
  • Personal vehicles cause 50% of transport GHGs
  • 10% of 50% = 5% of transport GHG emissions (= 10% abandon cars completely)
  • But, transport GHG emissions are only 26% of total US GHG emissions.  
  • So from bikes/walking replacing cars we have at most 5% of 26% = 1.3% of total GHG emissions.
1.3%  = the upper limit of how much GHGs would be eliminated by getting 10% of all commuters to abandon their cars completely for not only commuting, but also shopping, and recreation.  If abandoning cars applies only to commuting and they still use cars for other things, then it is at most a third of that 1.3% (about 0.5%) of GHGs would be eliminated by getting people to bike to work.

The final word:
Chevy Bolt - 100% electric - 238 Miles on a Charge - $25K after govt. incentives
Tesla Model 3 - 100% electric - 200+ Miles on a Charge - $25K after govt. incentives