Plot.plot({
marginLeft: 120,
padding: 0,
y: {label: null},
color: {legend: true, zero: true},
marks: [
Plot.cell(
traffic,
Plot.group(
{fill: "median"},
{x: (d) => d.date.getUTCHours(), y: "location", fill: "vehicles", inset: 0.5, sort: {y: "fill"}}
)
)
]
})