I assume routing software will prefer a trunk road over a primary road?
The way I've done it, primary roads are the main thoroughfare through an
area - the road most locals would choose when going *through*. I've
upgraded a few roads to primary due to their importance. You could
possible ask
it's possible that it can improve, or may in fact worsen the routing
computation (as far as time of estimated arrival of arrival is
concerned) , depending on the speed assignment of trunk (or primary).
if all trunk within the philippines have the same speed assignment,
then routing will
