When you enable traffic-optimized routing in your requests, the Routing API uses up-to-date traffic information to calculate the route. For example, a route calculation for the current time uses live traffic information.
When considering travel times in the future, this live traffic information is augmented with historical traffic speeds. In case of longer routes, the API combines live traffic information with historical traffic information for the later portions of the route. Routes calculated for trips in the future use historical traffic information to determine traffic speeds, and considers any long-term road closures on the route.
If the request does not include a departure time, the API assumes all current live traffic events (at the time of calculation) are valid for the entire length of the route and does not use any time-dependent information.
You can only enable traffic information for some types and transport modes. For more information, see Routing Mode Parameter Combinations.