{
  "version": 8,
  "name": "cyan line",
  "layers": [
    {
      "id": "road",
      "type": "line",
      "source-layer":"road",
      "paint": {
      "line-color": "#0099cc",
     "line-width": [
         "interpolate",
         ['exponential', 2],
         ['zoom'],
         5,1,
         20,8
     ]
    }
    }
  ]
}