Yes, I meant to add it.

@@ -8,0 +9 @@
+<ke_inf>&sK;</ke_inf>

こ線橋 could be [sK].

gg5
https://www.joetsu.ne.jp/12797
http://www.thr.mlit.go.jp/aomori/syutu/aokoku/gizyutu/080702furukawakosenkyouhosou/furukawakosennkyouhosou.html
https://dailyportalz.jp/b/2006/11/17/b/
跨線橋	85256	97.0%
こ線橋	2664	3.0%

Web results are dominated by footbridges but I found some examples of vehicle bridges.
I think this works.

@@ -5,0 +6,3 @@
+</k_ele>
+<k_ele>
+<keb>こ線橋</keb>
@@ -12 +15,2 @@
-<gloss>overpass(crossing a rail line)</gloss>
+<gloss>bridge over a railroad (esp. a footbridge)</gloss>
+<gloss>overpass</gloss>

Google N-gram Corpus Counts
跨線橋	85256
オーバーパス	4554

Overpass
https://en.wikipedia.org/wiki/Overpass
跨線橋
https://ja.wikipedia.org/wiki/跨線橋

Any dictionary should verify this. 
出典：デジタル大辞泉（小学館）
https://dictionary.goo.ne.jp/word/跨線橋/
鉄道線路の上をまたぐような形で架けた橋。渡線橋。

Looking at the n-grams (85,000 hits), this isn't a niche term and I think it's hopefully worth giving a bit more detail.

I don't know how jisho.org works precisely, but I think that the simple gloss of "overpass" has perhaps caused jisho.org to cross-reference the English-language wikipedia "Overpass" with the Japanese 跨線橋.  This is misleading, and the English "Overpass" wikipedia entry, while it has links to 40 other languages, specifically has no link to the Japanese site. There does not appear to be a comprehensive Japanese wikipedia entry for what westerners think an "overpass" would be.

The wikipedia entry for 跨線橋 contains only pictures of commonplace(in Japan), everyday pedestrian rail crossings.

I know jisho.org's behavior is not specifically jmdictdb's problem, but usually when jisho.org provides Wikipedia links for a term, it is a good sign that the term is the "canonical" term for whatever is linked.  That definitely is not the case here. (オーバーパス might be better, but it doesn't appear super-common in Japanese, and it has no wikipedia entry in any case).

If I had my druthers, I would also include "usually pedestrian". Both the dictionary definitions and wikipedia reference specify that vehicle bridges would be included, but it's exceedingly hard to find such examples.

@@ -12 +12 @@
-<gloss>overpass</gloss>
+<gloss>overpass(crossing a rail line)</gloss>