US Road Map (data from natural earth).
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<meta charset="utf-8">
<style>
.roads {
fill: none;
stroke-linejoin: round;
stroke-linecap: round;
}
.major-highway { stroke: #525252; stroke-width: 1.5px; }
.secondary-highway { stroke: #737373; }
.road { stroke: #bdbdbd; }
.beltway { stroke: #737373; }
.ferry-route { stroke: #4393c3; stroke-width: 1.5px; }
</style>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js"></script>
<script>
var width = 960,
height = 600;
var projection = d3.geo.albersUsa()
.scale(1100)
.translate([width / 2, height / 2]);
var path = d3.geo.path()
.projection(projection);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
d3.json("usroads.json", function(error, usroads) {
if (error) throw error;
svg.append("g")
.selectAll("path")
.data(topojson.feature(usroads, usroads.objects.usa).features)
.enter().append("path")
.attr("d", path)
.style("fill","none")
.style("stroke","#252525")
.style("stroke-width",1);
svg.append("g")
.selectAll("path")
.data(topojson.feature(usroads, usroads.objects.roads).features)
.enter().append("path")
.attr("d", path)
.attr("class",function(d) { return "roads " + d.properties.type.toLowerCase().split(' ').join('-'); });
});
d3.select(self.frameElement).style("height", height + "px");
</script>
https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js
https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js