[deadbabe]

Even if you find a pheromone trail, it doesn’t tell you what direction is home, or what path to take at branching paths. You need dead reckoning. The trail just helps you reduce the complexity of what you have to remember.

[viraptor]

The lack of information in ant trails (beyond "it exists here") leads to death spirals https://en.m.wikipedia.org/wiki/Ant_mill

[fmbb]

The very first sentence of the article you linked says this happens because they lose the pheromone track.

[viraptor]

It does, but the original paper is not as certain. (https://digitallibrary.amnh.org/server/api/core/bitstreams/8...) It suggests that the following is done "both chemically and tactually" in case of a circular path, although with just a minimal test.

[deadbabe]

How could they encode some kind of directional information into a trail?

[sdenton4]

You take the branch with the stronger smell to get home. The branching point is where the trail divides, as different groups branch out, and thus the way home has more pheromones. Follow the trail and you don't need to remember the direction...

Many animals detect and interpret smells as chemical gradients. We don't have the hardware for it, but plenty of others do.

[cma]

The trail also leads the other ants to food, hard for them to use your own dead reckoning.