Blotz have got some fairly impressive new highway pieces available.  These roadways are suitable for any 10mm modern or sci-fi game system such as Dropzone Commander or similar.  The ramps have a 2 inch raise over about 8 inches which looks right on the table and gives a a gentle enough slope for vehicles to stay on.  As with the rest of Blotz stuff these are laser cut MDF

https://www.facebook.com/BlotzTerrain/photos/pcb.423595121129789/423594914463143/?type=1&theater

They are available from their website;

http://blotz.co.uk/index.php?main_page=index&cPath=23_57_111

Taken from their Facebook update;

“New pieces are 1-lane on/off ramps, 30 degree curves and broken sections along with an entry/exit section for the 2-lane flyover (depending on which side of the road you drive on). Can be used to add a ramp to a different level (see pic) or simply to whizz off using the 1-lane flyover sections to elsewhere on the board.
All are now available via the website.”