yes, at the time of mapping, they made a near vertical face of the  soil-fill foundation (all this soil was brought in). Perhaps "retaining wall" is not the best tag, but is the closest I can see for this odd situation. All the other edges of this engineered soil foundation for the tolllway are contained by bridge abutments and concrete retaining walls at the base of the soil embankments down from the road surface. But here, on either side of the bridge abutments , are bare compacted soil "walls".  I think this is a very bad idea in Japan, but that is what it is. If you have a suggestion for a better tag, please message me and I will change it.