I’m finally getting somewhere! [:)] on layout design.
At one end the lines will vanish under some sort of (probably) concrete bridge structure carrying at least four lanes of traffic (maybe 6).
I have some pictures showing what these might look like from the track but I’m wondering whether structures like this were standardised by the 80s? I’m also wondering what road markings there would have been? The colour would seem to have been yellow for lane markings?
All and any information will lighten my almost complete darkness on this.
It would be the same as roads now, I think it’s been standard for many years. Solid yellow divides lanes going in opposite directions, so most roads would have two parallel yellow lines down the middle. One line or the other could change to stripes if passing was allowed in only one direction. If both can pass it would normally be one set of stripes. Solid white would indicate the outside of the lane.
Most Interstate Highways in Chicago would be Concrete with white dashed lines dividing the lanes and solid white lines defining the edges of the roadway (I guess that is what you want info on- those would be the majority of the 6-lane bridges) with the Concrete roadway supported by green steel beams on Concrete pillars. Plenty of weathering should be applied all around. Highway information signs (exit info, etc) are white letters on green background.
Would they have used this type of construction? I know that sort of bridge with those same blue-green beams is everywhere and were in widespread use by the late 80s. But in my head I’m thinking a lot of Chicago’s bridges would have predated the 1980s. Did they employ that ubiquitous color back in, say, the late 70s?
Never-ending Highway re-construction projects were in high gear during the late 70’s-thru the mid 80’s which brought about many hours of traffic frustration on my commutes to work.
Chicago’s south side Highways were mostly converted to the “new” green color scheme by the time I was transferred away from there in '87. Older bridges were riveted girders painted black with concrete roadways… Don’t forget the Chain link fencing (to prevent people from jumping off the bridge I presume.)
If you can find one, there was an Illinois DMV Handbook (Rules of the Road) from the mid-1970’s that had a photo on the cover of the Dan Ryan expressway, looking north. Immediately to the right (east) is the Penn Central/Rock Island lines complete with strings of jade green boxcars. On the left (west) was the CTA Howard-Dan Ryan (now Red Line) EL. It also had a pretty good view of several of the overpasses that you might be thinking of.
I know you asked about Illinois, but I worked for the Ohio Department of Transportation back in the 60’s and 70’s. When I first started all bridges maintained or built by ODOT were painted with Aluminum Paint and had Aluminum Handrails installed on the top of the Parapet Wall. As time went on the Aluminum Paint fell out of favor as it tended to streak and gray paint was used as the finish coat. Later they went to various pastel colors (as did Michigan) of light green, light blue but tended to stay with the light gray. And as pedestrian traffic left the bridges the Aluminum Handrails went away, which were a maintenance nightmare anyway with the corrosion problem caused by the galanized bolts used with the handrails. It was replaced by fencing due to the throwing rocks problem.