Accessibility

This site aims to meet WCAG 2.1 Level AA. Some of it exceeds that; some of it is still being improved.

Contrast. Every text and background pair on this page has been measured. The lowest ratio anywhere is 5.8 to 1 against a 4.5 to 1 requirement, and most text sits above 9 to 1. Colour is never the only way information is conveyed — directions carry arrows and labels as well as colour, and chart series are distinguished by line style as well as hue.

Text size. No text on this page renders below 13 pixels in the layout or 12 pixels inside charts. Uppercase labels use reduced letter-spacing at small sizes, which measurably improves word recognition.

Structure and keyboard use. Interactive controls are real buttons and inputs rather than styled divs, so they can be reached and operated by keyboard. Charts carry text alternatives describing what they show. Images have descriptive alt text.

Known gaps. The scrubbing sliders on the history charts convey their meaning through a moving visual, and while the underlying figures are also given as text, the experience is not equivalent for a screen reader user. Some dense data tables are difficult to navigate without sight. These are known and not yet solved.

If something here is not usable for you, write to the contact address at the foot of this page and describe what happened. Reports of specific problems are more useful than general ones and are acted on.