The Outer Wall, without a doubt, was the largest ring with the highest population. This meant that the streets and roads were often very crowded with people flooding through from all directions. It was a hassle to get around, similar to navigating some of the largest urban cities of the former Earth. One often had to leave very early to get a head start to reach their destination. The funny thing was, everyone thought this way.
As a result, the streets and roads were always congested with traffic. This was especially true in the downtown districts, but even the uptown districts weren't much less crowded. Because of this, various new forms of transportation were also designed. However, they hadn't yet reached the advancement level of teleportation.
To quickly avoid getting mixed up in whatever mess Huey had caused before it escalated, Lyra quickly bought a train ticket for the next ride, even though their destination was more or less within walking distance.