Which itself is a problem of global illumination. It's quite easy to mostly mask the lack of absolutely perfect ray tracing illumination by adding a basic ambie

Which itself is a problem of global illumination. It's quite easy to mostly mask the lack of absolutely perfect ray tracing illumination by adding a basic ambient illumination, but it has this sort of odd effect. The other problem is that the scene is too clean - there's no haze, or smoke which you'd expect from a highway shot.