It looks like you made the curved road edges using the arch tool - if you did, then that makes things a little easier.
Start by creating another 90* arch that fits snugly into the curve of the road (and of course, using the wall width of the sidewalk pieces).
Then go into vertex edit mode and select the first piece. Use Ctrl to select two edge midpoints on the top face, shown below:
And hit Ctrl+F to split the face.
Now select the two inner vertices on the top face and bring them down to match the sidewalk piece next to it. You will need to use the 1u grid to keep the vertices on their vertical axes. If you do this correctly, you won't get any invalid solids.
Repeat for the rest of the pieces in the curve.
Next, open the face edit tool. Select the vertical face of the first piece, and alt+right click on the sloped face above it. Do the same for the sloped face: select it, then alt+right click the horizontal face on top. This will align all three faces' textures.
Once you finish out the rest of the arch, you should end up with this:
Then you can do the other side of the curve the same way. Hope this helps!