I'm aware that in the industrial era it has been fairly common to dig tunnels through mountains to allow roads and railways to pass through, which improves the efficiency of the infrastructure since you don't have to go around every mountain or piece of elevated terrain. But I'm wondering if this was ever done in the pre-industrial era, say before the advent of railways?
I know tunneling was done on occasion in mines, to build sewage systems, or during sieges, but I'm specifically looking for examples of tunnels that were dug out in order to build a road through a mountain or similar, to make trade, logistics and travel more efficient, similar to how road- and railway-tunnels are used today.
If there are no such examples, or if they are very rare, why is that? What changed to make infrastructure tunnels more viable in the industrial era?
Yes, during the Roman Empire, many tunnels were constructed whenever a road met a huge geographical obstacle.Some notable examples are the Coeccius tunnel (1 km long) and the Furlo pass tunnel. Progress through hard rock could be very slow and it was not uncommon for tunnels to take years if not decades to be built. Construction marks left on a Roman tunnel in Bologna shows us that the rate of advance through solid rock was 30 cm (12 inches) per day.
I am not sure how much this practice carried over into the middle ages though.