Freeway rain shields (idea)

[hotdogPi]

I was thinking that some freeways could have a "shield" above them to protect from rain and snow. In addition, pedestrians could walk on it. It would not be strong enough for cars or houses, though; it would just be a way to connect the two sides of the freeway. Whether bicycles are allowed or not depends on the material being used for the shield; some materials would not provide enough traction. (It should be built to withstand a single car in case some car accidentally goes that way.)

This works best for freeways below ground level by at least 13½ feet. If the freeway is below ground level, but not by 13½ feet, there would be stairs so that there is a clearance of 13½ feet above the roadway. If the freeway is at ground level, the shield would have vertical walls at the edges, and if pedestrian access is desired, stairs would be put where needed instead of on the entire structure.

I am not sure what material would be best for this. It should be mostly transparent, but complete transparency is not required; e.g. there could be an opaque high-traction strip for bicycles, or there could be solar panels on the top.

I can see a few problems with this, but they can probably be fixed in one way or another:
* The grass inside the shield would die due to lack of water.
* Overhead signs would be harder to read in rain or snow, as the rain or snow on top of the shield is blocking sight.
* No ventilation.

[Max Rockatansky]

Not to mention it would only make Freeways even more of a bore to look at by taking away what little scenery is left.  I would imagine cost would likely be the biggest turn off more than anything.  What happens when a section of covering gets too much snow and falls onto a roadway?

[cbeach40]

There are a number of technical issues with this, all of which could be worked around for a price, but the necessity of doing this is questionable at best to me. Using Ontario as an example as a) we run the gamut of clear, rain, and snowy conditions, and probably more importantly b) I had the data on hand, crashes during rain/snow/freezing rain conditions made up 19.17% of the total number of collisions. However, for injury collisions those that occurred during rain/snow/freezing rain only made up 18.1% of total, while fatal collisions only 13.6% occurred during rain/snow/freezing rain conditions.

If one were to make improvements to deal with environmental factors, illumination would be more beneficial as darkness accounts for a greater proportion of fatal collisions (38% of all fatal collisions vs. 23% of all collisions).

[Edit/Addendum]

As far as capping depressed freeways, the chief advantage to that is improved connectivity for the surrounding neighbourhood. A bit of a simplified version of the Big Dig, where you have parkland above the freeway. Ontario's Highway 401 in Windsor did something like this, though that was new build. Hopping across the river, I-94 east of the GM Hamtramck plant would be a good contender to be capped in places. Can get around the ventilation and mitigate the cost issues by only doing it in short segments (max out at <240 m), and at strategic locations.

So really it's a great idea, but for the benefit of those around the freeway.