Use a getroute request to retrieve more information about a previously calculated route by specifying the routeId from a previously calculated route response. Make sure to use the same mode parameter (mode=fastest;car;). The traffic mode can be added arbitrarily.
Note: Since routeId is not a permanent identifier it can change with the map version. If the example getroute request is failing, then the below exampled calculate route request needs to be recalculated to acquire a fresh and valid routeId. The routeId parameter should be then replaced by the new one in the example getroute request.

Recalculation

https://route.ls.hereapi.com/routing/7.2/getroute.xml
?apiKey={YOUR_API_KEY}
&routeId=<YOUR_ROUTE_ID>
&mode=fastest;car
&maneuverattributes=position,link
&linkattributes=shape,DynamicSpeedInfo
&requestid=<YOUR_TRACKING_ID>
Note: This example uses a HERE API Key to authenticate your request. For the available authentication options, see the Identity & Access Management Developer Guide.