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Accessibility and the RSA-911 Graphs

Several accessibility issues were encountered while developing these dynamic graphs for the RSA-911 data. Many of the issues were due to technical limitations of the ColdFusion web scripting system being used. Some of these problems do remain, but we have worked to make these graphs and the information they represent as accessible as possible, given the current technology.

Text Alternatives for Images

The ColdFusion code for generating the graphs does not allow the use of 'ALT text' for the images, so any description of the image must appear either before or after the graph. Thus, the data in the graph is also displayed at the bottom of the page in data tables. These data tables can also be used by visitors who would like to generate their own graphs of the data.

Titles and Axis Labels

Graph titles and axis labels, as well as the data table titles and column headings, were carefully chosen to provide the context of the data. Column headings in the data tables are denoted using table heading tags to allow screen reader users to understand the tables more easily.

Bar Values

When the charts are generated, an image map is automatically generated that shows the labels and value of each bar when the mouse is placed over the bar in the graph. While this feature has some benefits in terms of cognitive accessibility, low vision accessibility, and usability, it is not very accessible for screen reader users or others who may have difficulty using a mouse.

Excessive Widths of Some Graphs

It was necessary to make the graphs that display data for all states very wide so that the labels for all the states would appear. If the graphs are narrower, ColdFusion automatically drops labels for the data along the x-axis to prevent overlapping labels. The text size was reduced slightly so that the graph would not have to be as wide, but that the text would remain readable. Browsers, such as Firefox, that can automatically scale figures to fit a page can be helpful, and printing in landscape mode decreases the chance that a graph will be clipped.

Color Selection

The colors used for graphing were also carefully selected so that users with color blindness or other visual impairments could still distinguish the information being displayed. Colors that appear the same to people with red/green or blue/yellow color blindness were avoided. In addition, the colors selected vary in brightness, and can be distinguished even in grayscale. For the graph showing RT, RE, ATS, and ATD, labels were added above each bar to assist in identifying them. Additionally, the legend appears horizontally in the same order that the bars appear so that the bars can more easily and reliably be matched up

File Formats for Graphs

Three different graphics formats have been made available: PNG, Flash, and JPG. Each of these has advantages and disadvantages. While Flash can present accessibility problems for screen reader users and can be problematic to print, it is has the best visual accessibility because it is a vector format, which means that the user can zoom in or out to any size without losing its quality or increasing its file size. PNG and JPG are better options for users who want to print or do not have the Flash player.

Feedback

Please contact us if you have any questions or comments regarding the accessibility of these graphs.

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