Canh chỉnh theo đường

Roads API thu thập tới 100 điểm GPS dọc theo một tuyến đường và trả về một tập dữ liệu tương tự, với các điểm được gắn với rất có thể là những con đường mà xe đang đi. Nếu muốn, bạn có thể yêu cầu nội suy các điểm, dẫn đến một đường dẫn tuân theo hình học của đường một cách trơn tru.

Yêu cầu

Yêu cầu chụp nhanh đường phải được gửi qua HTTPS và có dạng như sau:

https://roads.googleapis.com/v1/snapToRoads?parameters&key=YOUR_API_KEY

Required parameters

  • path

    The path to be snapped. The path parameter accepts a list of latitude/longitude pairs. Latitude and longitude values should be separated by commas. Coordinates should be separated by the pipe character: "|". For example: path=60.170880,24.942795|60.170879,24.942796|60.170877,24.942796.

    Note: The snapping algorithm works best for points that are not too far apart. If you observe odd snapping behavior, try creating paths that have points closer together. To ensure the best snap-to-road quality, you should aim to provide paths on which consecutive pairs of points are within 300m of each other. This will also help in handling any isolated, long jumps between consecutive points caused by GPS signal loss, or noise.

Optional parameters

  • interpolate

    Whether to interpolate a path to include all points forming the full road-geometry. When true, additional interpolated points will also be returned, resulting in a path that smoothly follows the geometry of the road, even around corners and through tunnels. Interpolated paths will most likely contain more points than the original path. Defaults to false.

Ví dụ

Yêu cầu sau sẽ gắn các điểm được chỉ định vào hình học đường. Tập dữ liệu cụ thể này đi theo một con đường hình tròn; việc đặt interpolate=true đảm bảo rằng hình học được trả về sẽ khớp với độ cong của đường. Với interpolate=false, đường dẫn được chụp nhanh vẫn sẽ đi theo đường, nhưng đường đa tuyến tính thu được sẽ không được mượt mà.

URL

https://roads.googleapis.com/v1/snapToRoads
  ?interpolate=true
  &path=-35.27801%2C149.12958%7C-35.28032%2C149.12907%7C-35.28099%2C149.12929%7C-35.28144%2C149.12984%7C-35.28194%2C149.13003%7C-35.28282%2C149.12956%7C-35.28302%2C149.12881%7C-35.28473%2C149.12836
  &key=YOUR_API_KEY

cURL

curl -L -X GET 'https://roads.googleapis.com/v1/snapToRoads?path=-35.27801%2C149.12958%7C-35.28032%2C149.12907%7C-35.28099%2C149.12929%7C-35.28144%2C149.12984%7C-35.28194%2C149.13003%7C-35.28282%2C149.12956%7C-35.28302%2C149.12881%7C-35.28473%2C149.12836&interpolate=true&key=YOUR_API_KEY'

Phản hồi

Đối với mỗi yêu cầu hợp lệ, Roads API sẽ trả về một phản hồi trong định dạng được biểu thị trong URL yêu cầu, chẳng hạn như phản hồi JSON sau đây.

{
  "snappedPoints":
    [
      {
        "location":
          { "latitude": -35.27800489993019, "longitude": 149.129531998742 },
        "originalIndex": 0,
        "placeId": "ChIJr_xl0GdNFmsRsUtUbW7qABM",
      },
      {
        "location":
          { "latitude": -35.2784195, "longitude": 149.12946589999999 },
        "placeId": "ChIJr_xl0GdNFmsRsUtUbW7qABM",
      },
      {
        "location":
          { "latitude": -35.2784195, "longitude": 149.12946589999999 },
        "placeId": "ChIJ6aXGemhNFmsRZE_zHqhmrG4",
      },
      {
        "location":
          { "latitude": -35.2792731, "longitude": 149.12933809999998 },
        "placeId": "ChIJ6aXGemhNFmsRZE_zHqhmrG4",
      },
      {
        "location":
          { "latitude": -35.2792731, "longitude": 149.12933809999998 },
        "placeId": "ChIJTcTdZ2hNFmsRXokM4mWCWfk",
      },
      {
        "location": { "latitude": -35.279557, "longitude": 149.1292973 },
        "placeId": "ChIJTcTdZ2hNFmsRXokM4mWCWfk",
      },
      {
        "location": { "latitude": -35.279557, "longitude": 149.1292973 },
        "placeId": "ChIJiUfNQmhNFmsRSsAI-1m6y1g",
      },
      {
        "location":
          { "latitude": -35.279610999999996, "longitude": 149.1292889 },
        "placeId": "ChIJiUfNQmhNFmsRSsAI-1m6y1g",
      },
      {
        "location": { "latitude": -35.2796484, "longitude": 149.1292791 },
        "placeId": "ChIJiUfNQmhNFmsRSsAI-1m6y1g",
      },
      {
        "location": { "latitude": -35.2796484, "longitude": 149.1292791 },
        "placeId": "ChIJ_RyFQ2hNFmsRoHJAbW7qABM",
      },
      {
        "location":
          { "latitude": -35.279947299999996, "longitude": 149.1291894 },
        "placeId": "ChIJ_RyFQ2hNFmsRoHJAbW7qABM",
      },
      {
        "location":
          { "latitude": -35.279947299999996, "longitude": 149.1291894 },
        "placeId": "ChIJOyypT2hNFmsRZBtscGL0htw",
      },
      {
        "location":
          { "latitude": -35.280323564795005, "longitude": 149.1290903128365 },
        "originalIndex": 1,
        "placeId": "ChIJOyypT2hNFmsRZBtscGL0htw",
      },
      {
        "location":
          { "latitude": -35.2803426, "longitude": 149.12908529999999 },
        "placeId": "ChIJOyypT2hNFmsRZBtscGL0htw",
      },
      {
        "location":
          { "latitude": -35.2803426, "longitude": 149.12908529999999 },
        "placeId": "ChIJr8xRTGhNFmsRzMb-rxgjspc",
      },
      {
        "location":
          { "latitude": -35.280409899999995, "longitude": 149.1290699 },
        "placeId": "ChIJr8xRTGhNFmsRzMb-rxgjspc",
      },
      {
        "location": { "latitude": -35.28048179999999, "longitude": 149.129062 },
        "placeId": "ChIJr8xRTGhNFmsRzMb-rxgjspc",
      },
      {
        "location": { "latitude": -35.2805541, "longitude": 149.1290623 },
        "placeId": "ChIJr8xRTGhNFmsRzMb-rxgjspc",
      },
      {
        "location": { "latitude": -35.280626, "longitude": 149.1290712 },
        "placeId": "ChIJr8xRTGhNFmsRzMb-rxgjspc",
      },
      {
        "location": { "latitude": -35.280626, "longitude": 149.1290712 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location":
          { "latitude": -35.280695099999996, "longitude": 149.12908489999998 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location": { "latitude": -35.2807629, "longitude": 149.1291046 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location": { "latitude": -35.2808294, "longitude": 149.1291306 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location": { "latitude": -35.2809064, "longitude": 149.1291693 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location":
          { "latitude": -35.280968200000004, "longitude": 149.129208 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location":
          { "latitude": -35.28101395754623, "longitude": 149.1292430025548 },
        "originalIndex": 2,
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location":
          { "latitude": -35.28103840000001, "longitude": 149.1292617 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location": { "latitude": -35.2810936, "longitude": 149.1293121 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location": { "latitude": -35.2810979, "longitude": 149.1293176 },
        "placeId": "ChIJv5r0smlNFmsR5nunau79Fv4",
      },
      {
        "location": { "latitude": -35.2810979, "longitude": 149.1293176 },
        "placeId": "ChIJpYMSrmlNFmsRXkCoIkZxgBg",
      },
      {
        "location":
          { "latitude": -35.281152399999996, "longitude": 149.1294256 },
        "placeId": "ChIJpYMSrmlNFmsRXkCoIkZxgBg",
      },
      {
        "location":
          { "latitude": -35.281152399999996, "longitude": 149.1294256 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2811784, "longitude": 149.1294706 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2812258, "longitude": 149.1295413 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.2812771, "longitude": 149.12960759999999 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.281332, "longitude": 149.1296695 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.2813904, "longitude": 149.12972670000002 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.281451700000005, "longitude": 149.1297788 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.28146506991143, "longitude": 149.12978858234607 },
        "originalIndex": 3,
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.28151580000001, "longitude": 149.1298257 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.28158259999999, "longitude": 149.129867 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.281666099999995, "longitude": 149.1299091 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2817377, "longitude": 149.1299379 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.281810899999996, "longitude": 149.1299602 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.281884999999996, "longitude": 149.1299765 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.28194399606459, "longitude": 149.1299842294294 },
        "originalIndex": 4,
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.281959799999996, "longitude": 149.12998629999998 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.282035199999996, "longitude": 149.1299895 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2821254, "longitude": 149.1299851 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location":
          { "latitude": -35.282199999999996, "longitude": 149.1299743 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2822739, "longitude": 149.1299573 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2823468, "longitude": 149.129934 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2824178, "longitude": 149.1299043 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2824379, "longitude": 149.1298945 },
        "placeId": "ChIJ601MoWlNFmsR5mvkfPp2ovA",
      },
      {
        "location": { "latitude": -35.2824379, "longitude": 149.1298945 },
        "placeId": "ChIJe9LPnWlNFmsR7mJw8mYHwG0",
      },
      {
        "location":
          { "latitude": -35.282472999999996, "longitude": 149.1298835 },
        "placeId": "ChIJe9LPnWlNFmsR7mJw8mYHwG0",
      },
      {
        "location": { "latitude": -35.2825375, "longitude": 149.1298525 },
        "placeId": "ChIJe9LPnWlNFmsR7mJw8mYHwG0",
      },
      {
        "location":
          { "latitude": -35.28257309999999, "longitude": 149.1298319 },
        "placeId": "ChIJe9LPnWlNFmsR7mJw8mYHwG0",
      },
      {
        "location":
          { "latitude": -35.28257309999999, "longitude": 149.1298319 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location":
          { "latitude": -35.282665400000006, "longitude": 149.12974459999998 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location":
          { "latitude": -35.28274030000001, "longitude": 149.1296645 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location":
          { "latitude": -35.282809799999995, "longitude": 149.12957799999998 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location":
          { "latitude": -35.28282136229385, "longitude": 149.12956142620385 },
        "originalIndex": 5,
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location": { "latitude": -35.2828744, "longitude": 149.1294854 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location":
          { "latitude": -35.282922299999996, "longitude": 149.1294044 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location":
          { "latitude": -35.282931500000004, "longitude": 149.1293876 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location": { "latitude": -35.2830263, "longitude": 149.1291788 },
        "placeId": "ChIJaUpThGlNFmsRMHWxoH7EOsc",
      },
      {
        "location": { "latitude": -35.2830263, "longitude": 149.1291788 },
        "placeId": "ChIJyd3JiWlNFmsR9RUq2ySTTZQ",
      },
      {
        "location": { "latitude": -35.283054, "longitude": 149.1290996 },
        "placeId": "ChIJyd3JiWlNFmsR9RUq2ySTTZQ",
      },
      {
        "location": { "latitude": -35.2830794, "longitude": 149.1290094 },
        "placeId": "ChIJyd3JiWlNFmsR9RUq2ySTTZQ",
      },
      {
        "location": { "latitude": -35.2830794, "longitude": 149.1290094 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.28313383700836, "longitude": 149.12893500604946 },
        "originalIndex": 6,
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.283134499999996, "longitude": 149.12893409999998 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.283190399999995, "longitude": 149.1288668 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location": { "latitude": -35.2832503, "longitude": 149.1288041 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location": { "latitude": -35.2833133, "longitude": 149.1287463 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location": { "latitude": -35.2833794, "longitude": 149.128694 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.283448299999996, "longitude": 149.128647 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location": { "latitude": -35.2835199, "longitude": 149.1286054 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location": { "latitude": -35.2835934, "longitude": 149.1285699 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.283668899999995, "longitude": 149.12854059999998 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.28372649999999, "longitude": 149.1285237 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.28386179999999, "longitude": 149.12849319999998 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location": { "latitude": -35.2839978, "longitude": 149.1284682 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.2840205, "longitude": 149.12846779999998 },
        "placeId": "ChIJWSb8ImpNFmsRp_4JAxJFE1A",
      },
      {
        "location":
          { "latitude": -35.2840205, "longitude": 149.12846779999998 },
        "placeId": "ChIJZe8tFWpNFmsR4brZ1vldk2E",
      },
      {
        "location":
          { "latitude": -35.2840524, "longitude": 149.12845969999998 },
        "placeId": "ChIJZe8tFWpNFmsR4brZ1vldk2E",
      },
      {
        "location":
          { "latitude": -35.284341500000004, "longitude": 149.1284124 },
        "placeId": "ChIJZe8tFWpNFmsR4brZ1vldk2E",
      },
      {
        "location": { "latitude": -35.2843875, "longitude": 149.1284034 },
        "placeId": "ChIJZe8tFWpNFmsR4brZ1vldk2E",
      },
      {
        "location": { "latitude": -35.2843875, "longitude": 149.1284034 },
        "placeId": "ChIJVx7Ta2pNFmsRx9OI9CnN5tI",
      },
      {
        "location": { "latitude": -35.2845916, "longitude": 149.1283726 },
        "placeId": "ChIJVx7Ta2pNFmsRx9OI9CnN5tI",
      },
      {
        "location": { "latitude": -35.2845916, "longitude": 149.1283726 },
        "placeId": "ChIJtWxAZmpNFmsRlbUCkc6VtnA",
      },
      {
        "location":
          { "latitude": -35.28459730000001, "longitude": 149.1283703 },
        "placeId": "ChIJtWxAZmpNFmsRlbUCkc6VtnA",
      },
      {
        "location":
          { "latitude": -35.284728747199374, "longitude": 149.12834860726772 },
        "originalIndex": 7,
        "placeId": "ChIJtWxAZmpNFmsRlbUCkc6VtnA",
      },
    ],
}

Phản hồi sử dụng lược đồ sau.

SnapToRoadsResponse

FieldRequiredTypeDescription
optional Array<SnappedPoint>

An array of snapped points.

See SnappedPoint for more information.

optionalstring

A string containing a user-visible warning.

SnappedPoint

FieldRequiredTypeDescription
requiredLatitudeLongitudeLiteral See LatitudeLongitudeLiteral for more information.
requiredstring

A unique identifier for a place. All place IDs returned by the Roads API correspond to road segments.

optionalnumber

An integer that indicates the corresponding value in the original request. Each value in the request should map to a snapped value in the response. However, if you've set interpolate=true or if you're using nearest roads, then it's possible that the response will contain more coordinates than the request. Interpolated values will not have an originalIndex. These values are indexed from 0, so a point with an originalIndex of 4 will be the snapped value of the 5th latitude/longitude passed to the path parameter. Nearest Roads points may contain several points for single coordinates with differing location or placeId.

LatitudeLongitudeLiteral

An object describing a specific location with Latitude and Longitude in decimal degrees.

FieldRequiredTypeDescription
requirednumber

Latitude in decimal degrees

requirednumber

Longitude in decimal degrees

Bản minh hoạ

  1. Nhấp xung quanh trên bản đồ để tạo một tuyến đường của xe. Xin lưu ý rằng nếu các điểm cách nhau quá xa, chúng có thể không chụp đúng cách.
  2. Nhấp đúp để gắn đường đi của bạn với đường.

Xem ví dụ này ở chế độ toàn màn hình.

JavaScript

var apiKey = 'YOUR_API_KEY_HERE';

var map;
var drawingManager;
var placeIdArray = [];
var polylines = [];
var snappedCoordinates = [];

function initialize() {
  var mapOptions = {
    zoom: 17,
    center: {lat: -33.8667, lng: 151.1955,}
  };
  map = new google.maps.Map(document.getElementById('map'), mapOptions);

  // Adds a Places search box. Searching for a place will center the map on that
  // location.
  map.controls[google.maps.ControlPosition.RIGHT_TOP].push(
      document.getElementById('bar'));
  var autocomplete = new google.maps.places.Autocomplete(
      document.getElementById('autoc'));
  autocomplete.bindTo('bounds', map);
  autocomplete.addListener('place_changed', function() {
    var place = autocomplete.getPlace();
    if (place.geometry.viewport) {
      map.fitBounds(place.geometry.viewport);
    } else {
      map.setCenter(place.geometry.location);
      map.setZoom(17);
    }
  });

  // Enables the polyline drawing control. Click on the map to start drawing a
  // polyline. Each click will add a new vertice. Double-click to stop drawing.
  drawingManager = new google.maps.drawing.DrawingManager({
    drawingMode: google.maps.drawing.OverlayType.POLYLINE,
    drawingControl: true,
    drawingControlOptions: {
      position: google.maps.ControlPosition.TOP_CENTER,
      drawingModes: [
        google.maps.drawing.OverlayType.POLYLINE
      ]
    },
    polylineOptions: {
      strokeColor: '#696969',
      strokeWeight: 2,
      strokeOpacity: 0.3,
    }
  });
  drawingManager.setMap(map);

  // Snap-to-road when the polyline is completed.
  drawingManager.addListener('polylinecomplete', function(poly) {
    var path = poly.getPath();
    polylines.push(poly);
    placeIdArray = [];
    runSnapToRoad(path);
  });


  // Clear button. Click to remove all polylines.
  document.getElementById('clear').addEventListener('click', function(event) {
    event.preventDefault();
    for (var i = 0; i < polylines.length; ++i) {
      polylines[i].setMap(null);
    }
    polylines = [];
    return false;
  });
}

// Snap a user-created polyline to roads and draw the snapped path
function runSnapToRoad(path) {
  var pathValues = [];
  for (var i = 0; i < path.getLength(); i++) {
    pathValues.push(path.getAt(i).toUrlValue());
  }

  $.get('https://roads.googleapis.com/v1/snapToRoads', {
    interpolate: true,
    key: apiKey,
    path: pathValues.join('|')
  }, function(data) {
    processSnapToRoadResponse(data);
    drawSnappedPolyline();
  });
}

// Store snapped polyline returned by the snap-to-road service.
function processSnapToRoadResponse(data) {
  snappedCoordinates = [];
  placeIdArray = [];
  for (var i = 0; i < data.snappedPoints.length; i++) {
    var latlng = new google.maps.LatLng(
        data.snappedPoints[i].location.latitude,
        data.snappedPoints[i].location.longitude);
    snappedCoordinates.push(latlng);
    placeIdArray.push(data.snappedPoints[i].placeId);
  }
}

// Draws the snapped polyline (after processing snap-to-road response).
function drawSnappedPolyline() {
  var snappedPolyline = new google.maps.Polyline({
    path: snappedCoordinates,
    strokeColor: '#add8e6',
    strokeWeight: 4,
    strokeOpacity: 0.9,
  });

  snappedPolyline.setMap(map);
  polylines.push(snappedPolyline);
}

$(window).load(initialize);

JavaScript + HTML

<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <title>Roads API Demo</title>
    <style>
      html, body, #map {
        height: 100%;
        margin: 0px;
        padding: 0px
      }

      #panel {
        position: absolute;
        top: 5px;
        left: 50%;
        margin-left: -180px;
        z-index: 5;
        background-color: #fff;
        padding: 5px;
        border: 1px solid #999;
      }

      #bar {
        width: 240px;
        background-color: rgba(255, 255, 255, 0.75);
        margin: 8px;
        padding: 4px;
        border-radius: 4px;
      }

      #autoc {
        width: 100%;
        box-sizing: border-box;
      }
    </style>

    <script src="https://www.gstatic.com/external_hosted/jquery2.min.js"></script>
    <script
      src="https://maps.googleapis.com/maps/api/js?libraries=drawing,places&key=YOUR_API_KEY"></script>
    <script>
var apiKey = 'YOUR_API_KEY_HERE';

var map;
var drawingManager;
var placeIdArray = [];
var polylines = [];
var snappedCoordinates = [];

function initialize() {
  var mapOptions = {
    zoom: 17,
    center: {lat: -33.8667, lng: 151.1955,}
  };
  map = new google.maps.Map(document.getElementById('map'), mapOptions);

  // Adds a Places search box. Searching for a place will center the map on that
  // location.
  map.controls[google.maps.ControlPosition.RIGHT_TOP].push(
      document.getElementById('bar'));
  var autocomplete = new google.maps.places.Autocomplete(
      document.getElementById('autoc'));
  autocomplete.bindTo('bounds', map);
  autocomplete.addListener('place_changed', function() {
    var place = autocomplete.getPlace();
    if (place.geometry.viewport) {
      map.fitBounds(place.geometry.viewport);
    } else {
      map.setCenter(place.geometry.location);
      map.setZoom(17);
    }
  });

  // Enables the polyline drawing control. Click on the map to start drawing a
  // polyline. Each click will add a new vertice. Double-click to stop drawing.
  drawingManager = new google.maps.drawing.DrawingManager({
    drawingMode: google.maps.drawing.OverlayType.POLYLINE,
    drawingControl: true,
    drawingControlOptions: {
      position: google.maps.ControlPosition.TOP_CENTER,
      drawingModes: [
        google.maps.drawing.OverlayType.POLYLINE
      ]
    },
    polylineOptions: {
      strokeColor: '#696969',
      strokeWeight: 2,
      strokeOpacity: 0.3,
    }
  });
  drawingManager.setMap(map);

  // Snap-to-road when the polyline is completed.
  drawingManager.addListener('polylinecomplete', function(poly) {
    var path = poly.getPath();
    polylines.push(poly);
    placeIdArray = [];
    runSnapToRoad(path);
  });


  // Clear button. Click to remove all polylines.
  document.getElementById('clear').addEventListener('click', function(event) {
    event.preventDefault();
    for (var i = 0; i < polylines.length; ++i) {
      polylines[i].setMap(null);
    }
    polylines = [];
    return false;
  });
}

// Snap a user-created polyline to roads and draw the snapped path
function runSnapToRoad(path) {
  var pathValues = [];
  for (var i = 0; i < path.getLength(); i++) {
    pathValues.push(path.getAt(i).toUrlValue());
  }

  $.get('https://roads.googleapis.com/v1/snapToRoads', {
    interpolate: true,
    key: apiKey,
    path: pathValues.join('|')
  }, function(data) {
    processSnapToRoadResponse(data);
    drawSnappedPolyline();
  });
}

// Store snapped polyline returned by the snap-to-road service.
function processSnapToRoadResponse(data) {
  snappedCoordinates = [];
  placeIdArray = [];
  for (var i = 0; i < data.snappedPoints.length; i++) {
    var latlng = new google.maps.LatLng(
        data.snappedPoints[i].location.latitude,
        data.snappedPoints[i].location.longitude);
    snappedCoordinates.push(latlng);
    placeIdArray.push(data.snappedPoints[i].placeId);
  }
}

// Draws the snapped polyline (after processing snap-to-road response).
function drawSnappedPolyline() {
  var snappedPolyline = new google.maps.Polyline({
    path: snappedCoordinates,
    strokeColor: '#add8e6',
    strokeWeight: 4,
    strokeOpacity: 0.9,
  });

  snappedPolyline.setMap(map);
  polylines.push(snappedPolyline);
}

$(window).load(initialize);
    </script>
  </head>

  <body>
    <div id="map"></div>
    <div id="bar">
      <p class="auto"><input type="text" id="autoc"/></p>
      <p><a id="clear" href="#">Click here</a> to clear map.</p>
    </div>
  </body>
</html>