My Honda gets about 20mpg. My BMW about 25mpg. Maybe I'm the exception that proves the rule, but I seriously doubt 30mpg is remotely close to average (for office workers) in the US.

Edit - The Ford F-150 is the best selling "car" in the US by a long shot. That isn't all fleet sales - a significant number of normal people own trucks for one reason or another (myself included - Honda Ridgeline).

Practically every ~10yo or newer sedan, wagon and "wagon pretending to be a crossover" you see is going to get nearly 30mpg (or more).

You need a heck of a lot of 10-15mpg vehicles to drag the fleet average down to 22. Most white collar employees who own trucks aren't commuting in them and even then there's more people commuting in 40+mpg subcompacts and hybrids so it should more than balance out.

Look at a high class parking garage, 22mpg just doesn't pencil out. 28-30mpg sounds believable.

You're vastly underestimating just how many people own massive inefficient pickup trucks and SUVs that they use for every trip. Maybe you happen to live in a part of the country where this problem isn't particularly bad, but the other parts of the country are driving that average down.

You're not understanding. The commuting miles saved by working from home is not going to be a cross section of the commuting population and the bits that are over-represented are going to be the white collar employees who skew toward more efficient vehicles so you have to pad the fuel economy or carbon estimates to reflect that.

I look in high class parking garages around me, and easily 1/3 of the cars are giant pickup trucks. Around here, tons of people will regularly buy a giant cab truck with a 6ft bed they'll mostly use to commute to an office job.

Welcome to Texas.

In a different thread, I found https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=40076 as a useful way of looking at CO2. That's got the Honda Fit as that's the one that was in discussion previously. Its a 33mpg car and the 'energy and environment' tab puts it at 4.4 tons/year. I've got a 2009 Honda Insight.

> Fuel cost estimates assume national average fuel prices and assume you drive 15,000 miles each year, 45% under highway driving conditions (steady speeds with little or no stopping) and 55% in city driving (low speeds with lots of stopping).

Noting that I'm not the typical home worker, but I went from an average of 600 miles/month (7200 miles/year) to 30 miles/month over the past year and a half. This took my carbon footprint for driving from 1.7 T/y to 0.1 T/y.

The flip side of this number is (for me) that I went from heating the house only a few hours a day in the winter to heating or cooling one room to comfortable. I don't have good numbers on my electrical footprint change. This would again be different with different life circumstances (number of other people in the house, size of house / apartment, etc...)