Two concentric rings of stacked bar segments show accident counts on a road, with the inner ring representing one day type and the outer ring another. Each segment’s arc length encodes a kilometer marker, while the radial extent shows the count for either the left or right lane, with the two lanes stacked in opposite directions from a central baseline. Built with D3 v4, the chart uses `d3.scaleBand` for angular positions, `d3.stack` with a custom opposing offset, and `d3.arc` for the ring geometry, rendering all elements as SVG. Data comes from a CSV file with columns for kilometer, holiday flag, and lane counts.