Surely it would be cheaper, as it would require no infrastructure, to restrict HGVs to motorways unless they have good reason to be on the trunk roads.  It is easily policed, forces the trucks onto the toll roads and keeps towns that have no bypass quieter thus not needing the expense of the bypass without 'killing off' such towns that would still be used by lighter traffic.

eg  If any truck that did not reasonably have l"Aldea on its itinerary (just passing through) it would have been on the AP7 paying toll and thus the cost of building the recently opened bypass could have been avoided or at very least postponed.

Just a thought!