# Traffic

The following chapter describes how to visualize traffic information and real-time traffic flows on the map using layer states.

## Show Real-Time Traffic Flow and Incidents on the Map

You can easily visualize traffic incidents on the map by enabling the map layer state trafficIncidents. The HERE SDK also supports a separate layer to see the current traffic situation. See the example below for how to show or hide a layer on the map.

After a layer is set, the visible area of the map is automatically updated. So you can freely pan the map in all directions to see the latest traffic incidents.

In many situations, drivers are interested in finding the fastest route based on the current traffic jams in a city - or outside a city. The HERE SDK allows you to show a layer holding all the current traffic jams, visualized by lines in different colors to indicate the severity of the jam - always updated in real-time. This feature requires an online connection and consumes slightly more data. However, the traffic lines are shown as part of the map tiles and are therefore highly performant.

Together - or independently - you can visualize such traffic information on the map with just a few lines of code:

do {
try mapView.mapScene.setLayerState(layer: MapLayerLite.trafficFlow, newState: LayerStateLite.enabled)
try mapView.mapScene.setLayerState(layer: MapLayerLite.trafficIncidents, newState: LayerStateLite.enabled)
} catch let mapSceneError {
print("Failed to enable traffic visualization. Cause: \(mapSceneError)")
}


Setting a new layer state is performed synchronously, but it requires a valid map scene that must have been loaded before. Also, setting a new layer state while a new map scene is being loaded, may result in an error. For hiding a layer, you can call the above with LayerStateLite.disabled instead of LayerStateLite.enabled.

The traffic flow lines are color coded as follows:

• Green: Normal traffic.
• Amber: High traffic.
• Red: Very high traffic.
• Black: Blocking traffic.

## Use MapSceneConfig to Enable More than One Layer Together with a New Map Scene

Sometimes it is more convenient to load the map scene using a MapSceneConfigLite. For example, if you want to enable visualization for traffic incidents, traffic flows and a new map scene at the same time, call this:

var mapSceneConfig = MapSceneConfigLite()
mapSceneConfig.mapLayers[MapLayerLite.trafficFlow] = LayerStateLite.enabled
mapSceneConfig.mapLayers[MapLayerLite.trafficIncidents] = LayerStateLite.enabled


Then implement the optional callback to know if loading the scene has succeeded:

func onLoadScene(errorCode: MapSceneLite.ErrorCode?) {
if let error = errorCode {
print("Error: New map scene not loaded: \(error)")
}
}


Here, the mapSceneConfig holds the desired layers, trafficFlow and trafficIncidents, together with their new state. By default, the initial state for both layers is disabled. When loading a new map scene, mapSceneConfig can be passed together with the desired map style as parameters.

For hiding both layers at the same time while setting a new map scene, you can call the above with .disabled instead of .enabled. Alternatively, you can independently control the state of a map layer using a synchronous call to setLayerState(layer:newState:) as shown above.