A bubble chart visualizes the relationship between vehicle speed, capacity, and energy source for various transportation modes. Each circle’s position encodes speed on the x-axis and capacity on the y-axis, while its radius scales with capacity and its color distinguishes energy source categories like Electric, Diesel, or Gasoline. Hovering reveals a tooltip with the mode, speed, and capacity. The chart uses d3.csv to load data, d3.scaleLinear for axes and bubble size, d3.scaleOrdinal with d3.schemeCategory10 for colors, and d3.axisBottom/Left for ticks.