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Latest UMTRI Eco-Driving Index shows 14% reduction of emissions per driver of newly purchased vehicles in US in April 2011 compared to October 2007

Eco-Driving Index (EDI) and the two sub-indices (EDId and EDIf) for October 2007 through April 2011. Source: UMTRI. Click to enlarge.

The most recent (April 2011) value of the University of Michigan Transportation Research Institute (UMTRI) Eco-Driving Index (EDI) stands at 0.86, indicating that in April 2011 there was a 14% reduction of emissions per driver of newly purchased vehicles in the US compared to the situation in October 2007.

The April 2011 index values for the two primary contributing variables—fuel economy (EDIf) and distance driven (EDId)—stand at 0.88 and 0.98, respectively. In other words, the decrease in emissions comes despite only a slight reduction in vehicle kilometers traveled.

The EDI is designed to estimates the average monthly impact on the environment by an individual US driver who has purchased a new vehicle that month. Environmental impact (emissions of CO2 and of other gasses and particulates) when using internal-combustion engines depends on the amount of fuel used. The EDI estimates this amount by taking into account two primary variables: the fuel economy of the vehicle and the distance driven. The EDI is developed and updated by Michael Sivak and Brandon Schoettle.

The index and the two sub-indices are computed monthly relative to their respective values in October 2007—the nominal start of the 2008 model year, the first model year for which the EPA started using the current fuel-economy rating system).

The EDI is computed by cross-multiplying EDIf and EDId. The lower the value of the EDI, the smaller the environmental impact.

EDIf is calculated as an inverse of the sales-weighted, average fuel economy of purchased new vehicles for each individual month. In turn, the average fuel economy (in mpg) is derived by Sivak and Schoettle from the monthly sales figures of individual models and the EPA fuel-economy ratings for the respective models.

EDId starts with the estimates of the total distance driven in the US for each month as issued by the Federal Highway Administration (FHWA). Sivak and Schoettle then adjust the raw distances to take into account (1) the seasonal variations in driving (in the US more driving is done in the summer than in the winter); (2) the varying number of days in a month; (3) the continuously increasing number of drivers,; and (4) the so-called rebound effect (increased amount of driving as a consequence of improved fuel economy of the new vehicle).

Future monthly values of the EDI will be issued with a lag of about 50 days (due to lags in the availability of the underlying data). The values for EDI, EDIf and EDId are available on the Eco-Driving Index (EDI) site.



We are slowly going in the right direction.

There are no secrets here:

Distance traveled (0.98) multiplied by consumption rate (0.88) equals total emissions (0.86).

Those are the two main factors affecting total emissions. They are still much too high.

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