As fleet efforts to reduce emissions grow more sophisticated and comprehensive, corresponding metrics to track progress must similarly evolve. Simply comparing a fleet's total of hybrid or alternatively fueled vehicles to benchmark success is no longer sufficient. A new generation of metrics must be developed around the ultimate goal of modern "greening" efforts: reducing greenhouse gas (GHG) emissions.

A free, online calculator created by Environmental Defense Fund (EDF) and NAFA Fleet Management Association enables any fleet with fuel consumption data to quickly find their emissions levels. With emissions data in hand, fleets can compare performance between internal units and external peers by indexing emissions along multiple characteristics, such as fleet size and mileage.

Use Comparable Units

As with all types of benchmarking, companies must use consistent and comparable units in tracking environmental performance. The most common unit used to measure GHG emissions is metric tons. For fleets seeking to compare environmental performance with peers, metric ton should be the base measure.

Clearly identifying the specific emissions tracked is also important; are fleets tracking only carbon dioxide or all vehicle greenhouse gases? While carbon dioxide is the easiest greenhouse gas to quantify, full GHG accounting from vehicles requires tracking emissions of methane, nitrous oxide, and refrigerants.

Fleets can utilize the environmental metrics outlined in this article to benchmark efforts internally and with peers. Given their multifaceted nature, fleets best pinpoint progress by tracking a series of metrics. For example, a fleet's total GHG emissions might be increasing because its vehicles are driving more miles, even if the vehicles themselves are more efficient. Each data point is critical to effectively managing fleet GHG emissions.

Metrics Just the Start

The metrics described are not comprehensive. Rather, they can help jumpstart a conversation within the fleet community about the best environmental metrics currently available to track progress. EDF encourages readers to share with us other metrics they have found useful, especially concerning how best to benchmark items such as idle time and routing efficiency.   


Fleet Greenhouse Gas Metrics

Total Greenhouse Gas Emissions
The total amount of emissions is the best measurement to assess overall environmental impact. Minimum data requirement: volume of fuel (by type) consumed.

The Environmental Defense Fund-NAFA online calculator estimates non-carbon dioxide greenhouse gas (GHG) emissions from this data. Unit: metric tons.

Greenhouse Gases per Miles Traveled
Miles traveled is a leading factor in determining vehicle emissions. It’s tough to compare the performance of units or peer entities that have different mileage patterns. This metric allows fleets to make a consideration for mileage, thus enabling comparisons between these groups.

Derivatives of this metric include greenhouse gases per a specific mileage quantity (i.e. 100 or 10,000 miles) and emissions per kilometer. Minimum data requirement: total emissions and total miles. Unit: kilograms.

Greenhouse Gases per Vehicle
This metric represents the average performance of the unit or company-wide aggregate of vehicles. It is influenced by factors including fuel source, miles traveled, and fuel economy. Fleets willing to “deep dive” into their data can produce a similar, unit-level metric that will help track the performance of individual operators of same models and identify which units contribute most to their overall footprint.

Minimum data requirement: total emissions and number of vehicles for total fleet average. For a vehicle-specific number, unit-specific fuel consumption data is required. Unit: metric tons.

Greenhouse Gases per Ton of Freight Moved
This cargo-based metric quantifies the efficiency of moving goods. By using tons instead of pallets or cases, fleets ensure their metric is consistent internally and comparable externally. Minimum data requirement: total emissions and tons of freight moved. Unit: kilograms.

Cost per Metric Ton of Greenhouse Gases Reduced
Different emission reduction strategies imply different costs. Some advanced-technology vehicles require more capital up-front. Driver training courses, routing software, and telematics all typically have costs. Fleets can compare their progress in seeking the most cost-effective strategies to reduce emissions by collecting emissions and cost data.

Minimum data requirement: Expenditure difference between the emission reduction effort and baseline case. This should include both capital expenses (and savings) and operating savings. Total greenhouse gases reduced from baseline. Unit: U.S. dollars spent per metric ton of greenhouse gases reduced.

Percentage of Fleet Vehicles Emitting Less Than 15, 10, and 5 Tons per Year
The GHG per-vehicle metric is important to assess the average performance of fleets. However, for diverse fleets, it can fail to tell the full story. This metric aims to examine changes in the population of different fleet segments.

In 2008, the average fleet vehicle emitted 15.1 metric tons of greenhouse gases, according to a 2009 State of Green Business report from Greener World Media ( Using this metric, fleets can see what percentage of their fleet performs better than the average fleet vehicle. Using further benchmarks, such as 5 and 10 tons, fleets can track the evolution of their fleets toward lower-emission vehicles. Minimum data requirement: Vehicle specific fuel consumption. Unit: metric tons.

Percentage of Drivers Matching or Exceeding EPA MPG Combined Rating
The Environmental Protection Agency (EPA) tests passenger vehicles for fuel economy using three numbers: city and highway mileage, and a combined average that assumes a 60/40 split of city and highway driving. Fleets can monitor success of their driver training programs by tracking progress in maximizing vehicle fuel economy. Minimum data requirement: Model-specific numbers on EPA combined fuel economy rating, vehicle-specific data on mileage, and fuel consumption. Unit: miles per gallon.