How can you switch from a heightend Highway to a ground highway? I can't seem to connect them together.

Can monorail go over or under a highway?

1. special tile iirc (search the menus)
2. can't go under, only go over ground highways.

Thankx! I'll search those menus some more.

To go from elevaded highway to ground highway you simply create some ground highway and elevaded highway close to where you want them to connect. Then you take either of them and you drag it into the other one.

Note: Be sure that you are not near a freeway ramp, interchange, or where a road may pass under a freeway because that will make it not work.

As dutchmetal said, you can't put monorail or elevaded rail overelevaded highway.