We pull a caravan and at present picking the fastest route can take us on unclassified roads. Is there anything that can be loaded which would ensure only main routes will be considered? This is in the UK only. I.m assuming a similar requirement would be made by HGV drivers!
I know Garmin do different products for truck drivers that take into account the size of the vehicle, not sure if TomTom do these as well, otherwise you will need to set the avoidances to make sure only major routes are used.