This D3.js example visualizes traffic accident distribution by weather condition as an interactive pie chart. It loads CSV data from a GitHub gist, aggregates accident counts per weather category using `d3.rollups`, and renders SVG pie slices with labels and a legend. The chart uses `d3.pie`, `d3.arc`, `d3.scaleOrdinal` with `schemeCategory10`, and a reusable `pieChart` function pattern with configurable width, height, and data properties. The visualization displays weather types directly on slices and provides a side legend with count values.