Maybe I didn't make it clear. Prior to the upgrade it would calculate the arrival time for a 60 mile journey with 55 miles motorway as around 60 minutes, which is pretty much on the money. It would then update the arrival time based on how close you are to the pre-determined parameters e.g. motorway 70mph, A road 45 mph, etc. The faster you go the shorter the arrival time and vice-versa.

Now the same 60 mile route is calculated as 145 minutes. Way off the actual travelling time. Once I reach the motorway it adjusts the time to a more realistic value but only based upon my current speed. The dynamic route planner takes TMC traffic incidents into consideration and works out all alternate routes based upon road type (motorway, A & B roads, etc.) and actual traffic delays, and then selects the best route based upon time. It can't do that accurately with my present issue.

Lets say you have 2 routes each 50 miles in length: Route 1 is 50 miles of B road (max speed 30mph) and route 2 is 1 mile of B road and 49 miles of motorway (max speed 70mph). Assuming all traffic is clear Route 2 should be far quicker, and prior to the upgrade it would work out that way. Now it generates the same arrival time for both routes until I get onto the motorway.