I came across a car reviewing website the other day, they include the standard auto test consumer stuff, how the car drives, practicality etc but they also include real world figures for both economy and emission data.
It came to my attention that in recent months, helped by the VW emissions scandal, people have started caring more about more than just economy, and that emissions can be just as important depending on your geographical location. Currently Fuelly only tracks fuel economy, but it would be pretty sweet if other factors like N0x, C02, and other tailpipe elements were to be tracked too, giving people a better understanding of the true environmental impact of thier car, and not the biased dramatised junk the media reports. See the screen shots below, you set the parameters for annual mileage, average fuel economy and driving style, and it calculates your emissions data based on those figures. I don't want to have too much confusing data compiled on fuelly, but I like this idea.
And it's also interesting to compare, as it takes into account the energy and emissions used to produce the vehicle and the fuel itself, a Nissan Leaf is actually responsible for the same carbon dioxide, nitrous oxide and particulate matter as a 5.0 litre Mustang. The eco heads won't be happy...
Plug in emissions comes down to their efficiency and what they are charging off of. Lots of coal burned for their power, and yes they can be dirty. Renewable and nuclear thrown into the mix and they'll clean up really quick.
There two big advantages to plug ins over the ICE. One is that the owner has an option in most regions in buying cleaner electricity, or making it themselves. While biofuels could possibly be made or bought by a person for the ICE, virtually all cars on the road can't use 100% biofuels. Some can't go higher than 5 or 10 percent. Then the fuels may only reduce the amount of NOx and particulates, if at all.
The other advantage is that the EV emissions are at the power plant, and not in the middle of town as with an ICE.
The EPA has more limited info in the side by side comparisons under the environment tab. The site doesn't include the car's manufacturer emission, and only goes beyond the tailpipe for CO2.
CO2 emissions are directly related to fuel economy. The amount of carbon per unit of fuel type is a known. So it just some basic math getting an users CO2 emissions from their fuel efficiency.
The other emissions reported are estimated from the amounts measured from the official tests, which are measured in g/mile or kilometer. Digging the actual values of a model from the EPA will be a pain, but a high estimate can be reported based on the car's emission bin. The only hiccup there is that manufacturers tend to certify their cars for a worse emission bin in federal states vs. CARB ones, even if the car has all the same equipment. It saves them some on warranty costs.
I also notice they issue a "rating" between 0 and 100 (0 being the greenest) for every vehicle based on all these factors, vehicle production, fuel production, tailpipe emissions etc. Some of it is subjective of course, every vehicle owners circumstances are different, but overall, it helps consumers understand the cars you might think are very "green" might not be as green as you initially think.
Thier lifetime "pence per mile" estimates are also very helpful for potential long term owners, and those sceptical about the maintenance/running costs of alternative fuel/hybrid vehicles.