Data Collection Methodologies

This page describes the data collection methodologies for the Alternative Fuels and Advanced Vehicles Data Center's (AFDC) database-driven Web tools. The following information outlines how the data is collected and shows the AFDC's maintenance schedules.

Alternative Fuel Station Data

Methodology: The data in the Alternative Fueling Station Locator and Route Mapper are gathered and verified through a variety of methods. The National Renewable Energy Laboratory (NREL) obtains information about new stations from trade media, Clean Cities coordinators, a submittal form on the Alternative Fuels and Advanced Vehicles Data Center (AFDC) website, and through collaborating with infrastructure equipment and fuel providers.

Existing stations in the database are contacted at least once a year on an established schedule to verify they are still operational and dispensing the fuel specified. Based on an established data collection schedule, the database is updated once a month. Currently, electric vehicle supply equipment (EVSE) is updated twice a month. Stations that are no longer operational or no longer provide alternative fuel are removed from the database on a monthly basis or as they are identified.

NREL regularly compares its station data with those of other relevant trade organizations and websites. Differences in methodologies and inclusion criteria may result in slight differences between NREL's database and those maintained by other organizations. NREL also collaborates with alternative fuel industry groups to maintain the data. NREL and its data collection subcontractor are currently collaborating with natural gas, electric drive, biodiesel, ethanol, and propane industry groups to establish best practices for identifying new stations in the most-timely manner possible and to develop a more rigorous network for the future.

Station addresses are geocoded and mapped using an automatic geocoding application. The geocoding application returns the most accurate location based on the provided address. Station locations may also be provided by external sources (e.g., station operators) and/or verified in a geographic information system (GIS) tool like Google Earth, Google Maps, or Google StreetView. This information is considered highly accurate and these coordinates override any information generated using the geocoding application.

A station appears as one point on the map, regardless of the number of fuel dispensers at that location. For electric charging stations, or EVSE, each location appears as a point on the map and additional details are provided to indicate the number and type of charging outlets at each location.

Caution: The AFDC recommends that users verify that stations are open, available to the public, and have the fuel prior to making a trip to that location.

Document Database

Methodology: NREL maintains a database comprised of thousands of documents related to alternative fuels, advanced vehicles, fuel economy, idle reduction, and more. As new publications are produced by the U.S. Department of Energy (DOE) Clean Cities inititative and other transportation-related DOE programs (including FreedomCAR, Biomass, and Hydrogen), they are added to the database. Documents developed by other government sources and industry are reviewed for their relevancy and added to the database if they fit criteria.

NREL obtains author approval before adding non-DOE documents to the database. When approval is not obtained but the document is deemed valuable, a citation and link to the document on another Web source is posted.

State and Federal Incentives and Laws

Methodology: NREL's database captures state and federal laws and incentives related to alternative fuels and vehicles, air quality, vehicle efficiency, and other transportation-related topics. State-level information is updated annually after each state's legislative session ends. Information for these updates is obtained from state legislative sites when the sites are deemed accurate and timely or by calling specific state offices directly. In addition, NREL maintains a resource list of the most useful websites and contacts for every state, as well as a list of search terms states routinely used in website searches.

Federal information is updated after enacted legislation is signed into law or when rules are issued by the responsible agencies. Existing information is reviewed at the same time new information is added to ensure it is still accurate and in effect.

Caution: The AFDC recommends that users verify with the appropriate state or federal authority that the specific law or incentive is still applicable before making a purchase or tax-related decision.

Truck Stop Electrification Site Locator

Methodology: The Truck Stop Electrification (TSE) Site Locator was developed as a collaborative effort between the Federal Highway Administration and the U.S. Department of Energy. It displays public truck stop locations that have idle reduction facilities for heavy-duty trucks. There are two types of truck stop electrification facilities in our database, and some require special equipment to be installed on the truck. To learn more about the types of systems and connections, visit the Shorepower, CabAire, EnviroDock, AireDock, and IdleAir websites.

NREL collects the data in the Truck Stop Electrification (TSE) Site Locator from Shorepower, CabAire, IdleAir, AireDock and EnviroDock websites. NREL, in turn, verifies the information (including station name, address, phone number, hours of operation, directions, etc.) by calling the fueling sites directly.

The verification process for all records occurs approximately every six months. In addition, NREL continually checks Web sources to determine if new sites have been added. If a new TSE site is found, NREL adds it as soon as possible.

The addresses for the sites are geocoded and mapped using a mapping application. If an exact address is not found, the TSE site is mapped in the center of the zip code, which may appear on the map at a considerable distance from the station's actual location.

Caution: The AFDC is aware that slight differences may be noted when comparing its data to that on the IdleAir and Shorepower sites. As previously mentioned, NREL verifies all TSE site data by calling the TSE sites directly. However, the AFDC recommends users additionally verify TSE site locations to ensure they are operational prior to making a trip.

Vehicle Search - Light Duty

Methodology: Vehicle specifications, photos, and pricing used in this tool are gathered from Kelley Blue Book data, information posted on websites of original equipment manufacturers (OEMs), and information provided by representatives of OEMs. Fuel economy figures come from the U.S Environmental Protection Agency (EPA). The vehicles and their specifications are updated as new models are released and/or changed. NREL conducts a comprehensive update of this database each fall based on new model year vehicles.

Caution: The AFDC recommends users check with their local dealers for more specific vehicle information before making purchasing decisions.

Vehicle Search - Heavy Duty

Methodology: Information about alternative fueled medium- and heavy-duty vehicles, engines, and hybrid propulsion systems is gathered from specifications posted on websites of original equipment manufacturers as well as information provided by vendor representatives. Vehicle specifications are updated as new models are released and/or updated. NREL conducts a comprehensive update of this database annually.