To investigate the sensitivity of MOVES to various factors that are internally modeled as affecting energy and emission rates (such as vehicle source type, onroad vehicle activity, and ambient environment inputs), the research team developed the MOVES sensitivity Analysis Toolkit. The online toolkit is composed of the sensitivity analysis function (script in Python 2.7) and a web interface. The web interface helps user edit and submit input variables they want to include in their sensitivity analysis. For example, users can specify a city, year, season, temperature, humidity, fleet composition, or duty cycle inputs. Users can provide a single input value or a range of input values through the interface (Figure 4). The MOVES-Matrix system is queried for emission rates using the range of GUI input values provided. To generate 2-d sensitivity analysis plots for the user selected inputs, the result page deploys d3.js, a JavaScript library for manipulating documents based on data, often used for web visualization. Figure 5 illustrates an output for CO2 sensitivity to operating mode bin (for a submitted driving cycle) and vehicle age. Users also receive the hourly energy data use in kilojoule per hour and emission rate data (CO2, PM2.5, NOX, etc.) in grams per hour for all input scenarios. Users can then use the data in their own independent analyses.