Roman legions marched around 30 km/day [0], carrying their own supplies, food, weapons and armour, needing to spend time making and breaking camp each day.

Modern European pilgrims on the Camino de Santiago seem to do about 20 km/day [1] and it's considered tiring but accessible by average people, not serious hikers. They carry less of their supplies and do not need to fortify their camp against barbarians.

Roman soldiers were presumably fitter and better trained than the average Roman (though maybe not by much, since everyone worked manual jobs). Maybe that's enough to account for the difference.

[0] https://www.quora.com/Did-Roman-legions-actually-march-20-mi...

[1] https://caminoways.com/how-many-days-does-it-take-to-walk-th...

> A random Western today or a random Roman then?

Probably better to compare "A random Italian" rather than "A random Westerner", the Americans and other car-focused cultures kind of drag down the average a bit too much otherwise.

Probably a random Roman. People used to walk a lot, often barefoot. The random modern Westerner would get blisters within the first week.

Probably the Westerner with better shoes, clothes, energy bars, hydration drinks, sunscreen etc.

The only caveat since you said "random" is obesity.

When I was in my late teens, I used to hike with a 15 kg backpack (with the technology of the late 80s). I could walk about 15 km in average hills over 8-10 hours.

I was average, physical capacities wise.

Eh, I'd say it's equal.

I've walked for 8 hrs before, wearing modern sneakers on roads with vehicular traffic, and travelled about the same distance estimated by Google Maps. I'd estimate the Roman would like be able to travel in the same duration, barring other extenuating factors (like Caesar staging a revolt against the Senate and crossing with his legion right in front of your planned route), with worse shoes but more walk-friendly roads.