Update on progress: It's slow going as I'm working multiple aspects of the layout along the critical path to completing the roads (i.e. ballasting, backgrounds, finishing rear buildings). I'll constrain the updates here to those actions directly related to the roads themselves in case its useful to anyone seeking to do something similar.
(1) Ramp Issues Resolved: The Nova has no issues with the ramp, but the Mustang was not so inclined (pun intended). The rear tires couldn't get purchase on the smooth MDF, even with extra weight added over the rear axle (I used tungsten cylinders intended for pinewood derby cars - it was enough weight to slow the car down, but not enough to noticeably help traction). I finally had to admit defeat and add some fine grit sandpaper to the "up" ramp. I did a quick function test before committing:
Here's the traction-assist sandpaper on the up ramp. It'll be pretty well hidden once all is said and done:
(2) Tunnel Entrance Cover: Tunnel entrance has been Bondo-ed and sanded smooth for a rounded look. I plan to some some decorative detail on the sides, plus may have some freeway signs hanging from the top inside. Mark, I'm ~70% confident it will come out looking cool... but if it doesn't, I can always do something different:
(3) Roadway and adjoining sidewalks: So far, I have the roadway filled, sanded, and painted - plus I have all the sidewalks/foundations for the buildings cut, scored, and painted a base color. Some sidewalks have also been installed.
Here are some sidewalk/foundations in place with lines for scoring marked. For some I just used MDF. In some places, I used paint stir sticks to help "square off" the area (for laziness reasons):
The MDF piece covering the back half of the ramp will be removable for access & mx:
Once all the sidewalks were fit tested and marked for sidewalks I removed them for scoring/painting., then starting filling the roads. Here I used lightweight spackle to fill all the cracks in the roads. Orbital sander with find grit paper worked great for sanding this smooth once it dried:
While the spackle dried I scored all my sidewalks and added some cracks. For MDF, a good wood burner works great in quickly making these score lines nice and clean:
Here roads are sanded and painted. Paint applied to roads with a high density foam roller:
Concrete pad for gas station:
Starting to pretty-up the tunnel:
...and finally, I installed some of the completed sidewalk/foundation sections. I glued them in place using a little wood glue and caulked the gaps between them and the road for a nice smooth curb. This works best if the bead on the caulk is as small as possible. Buildings still present on the table in pics below will have the sidewalks built around them as they don't need a foundation:
