There is now a shift from announcing the good news to expecting God's arrival. The good news (Isaiah 40:1–2) is based on God himself.
Isaiah described the Lord as coming on a highway through the desert (see Isaiah 35). However, the imagery is reversed here: In Isaiah 35, the people traveled to Zion, toward the Lord. Here, the Lord is coming toward his people (see also Isaiah 52:8, where both images are combined).