There will be encounter tables that are challenging for low level parties (or suicidal) but ho-hum for higher level parties or large convoys. No real insight there. It is often boring and time consuming to roll through those encounters once you are well beyond them having a threat. The time consuming part especially as life intrudes more and more on your time available for gaming with age.
A Hit Die number for each hex. Pass this HD number in your party and you "travel by map" right through the hex. Nothing in there will bother you and they will generally stay away from your party.
This could be small for roads that have only the odd highwayman (a Hit Die value of 5 or 6) or it could be huge if you are going near an enemy army (a Hit Die value of 10,000).
Events could also raise those numbers (secretly or openly). If a city is sacked and the countryside if full of extra bandits the number might go from 5 to 20. If a monster moves into a forest but hasn't yet been publicly exposed the number might go up by say double its HD (you'd need enough of an edge its no real worry).
For higher level hex crawls this has the effect of opening up more of the map without spending 2 hours of game time arriving, while also ensuring low level characters have to have serious worry about crossing the dark woods to make it to the city without the protection of a caravan or some such.