When I reached the next pedestrian accessible bridge to get off of Herr’s Island/Washington’s Landing (after having got on it by the converted railroad bridge), the question of what is a bridge stared me in the face. I’ve skirted that question since starting this blog, sometimes alluding to it in passing, but never really dealing with it head on. It came up first with Heth’s Run Bridge. While in the posts on this bridge (see Part I and Part II) I mention that the deep ravine that the bridge once spanned has been filled in, I don’t discuss what this means for the structure’s status as a bridge. The question there is: Is a bridge still a bridge if what it bridged has been filled in and the bridge isn’t actually bridging anything anymore?
Then, when I wrote about the Bridge Under a Bridge, I couldn’t help wondering if it was cheating to include this bridge as it was purely an aesthetic bridge built so that a man-made pond could go underneath. A different aesthetic choice could have led instead to a path bordered by two man-made ponds. Yet I still refused to address the question of what is a bridge?
At this point, I feel it is necessary to face the question, this point being where the 30th Street Bridge connects to the River Avenue ramp which connects to the 31st Street Bridge. From the view pictured above of the 30th Street Bridge, it looks like a bridge. However, from where I got on it (the lower end on the left side in the image above) it looked to me like a ramp taking traffic from a low point to merge onto another road at a higher elevation. Besides, it connects to the River Avenue ramp and in the junction of these two structures (pictured below), it felt like one continuous ramp system. Yet, a portion of this system is called a bridge. So I ask myself, “what is a bridge?”
First, I thought, “a bridge is a structure that connects two points which would otherwise not be accessible to each other.” Then I realized this definition includes ramps. In my current example, there is no other way that River Avenue, which for most of its course runs at the same level as the bike path in the picture above, would be able to access the 31st Street Bridge without a ramp. Therefore, according to my definition above the ramp is a bridge.
Another thought I had was “a bridge is a structure that spans a geological obstacle.” Well then, that means that the bridges that only exist to cross over a road or railroad aren’t really bridges. I discuss these types of bridges some in my post on Cleveland Bridges. In that post, I don’t question whether or not they are bridges, but whether they are significant enough to be counted in comparing the number of bridges cities have. Though I didn’t state it, I also wondered if they were significant enough for me to include these types of bridges in my bridge walking. Regardless of their significance, I consider them bridges.
Merriam-Webster defines a bridge as “a structure carrying a pathway or roadway over a depression or obstacle.” This definition seems pretty good as it excludes ramps but includes the bridges over man-made obstacles. I’d say this definition also would include the Bridge Under a Bridge. However, it doesn’t address the situation of Heth’s Run Bridge prior to its renovation. What if the structure “carrying a pathway or roadway” at one time crossed over “a depression or obstacle,” but does so no longer though the structure is still there? Is it still a bridge?
There is one other dilemma suggested by the 30th Street Bridge/River Avenue Ramp/31st Street Bridge structures, the Fort Duquesne Bridge, the Veterans Bridge, and London’s Jubilee Bridge. This dilemma is perhaps best expressed by “what makes one bridge?”
In the Veterans Bridge example, three separate structures cross over the obstacle of the lower elevation of the parking lots in the Strip before joining to become one structure across the obstacle of the Allegheny River. So, is this one bridge or three?
When I walked the Fort Duquesne Bridge, I was walking a pedestrian bridge built approximately 40 years after the Fort Duquesne Bridge. The pedestrian bridge is attached to the Fort Duquesne Bridge over the Allegheny River, but on either end it is separate with its own supports. Is this one bridge or two?
London’s Jubilee Bridge has two separate pathways, but one name and dedication date. They are separated by a bridge for the underground, which, as far as I can tell, they are attached to for structural support. So is this one, two or three bridges?
The 30th Street Bridge/River Avenue Ramp/31st Street Bridge structures appear to me to be one conglomeration, similar to the three structures that merge in the Veterans Bridge. Yet while the elements in the Veterans Bridge appear to be considered one structure, the 30th Street Bridge is considered a separate structure from the 31st Street Bridge, at least in so far as it has its own name and its own page on PGHbridges.com. What makes the 30th Street and 31st Street bridges different from the other examples I’ve listed above?
For a continuation of this discussion see What is a Bridge? Pittsburgh Edition II
Other posts in this series:
What is a Bridge? Pittsburgh Edition II (July 27, 2012)
What is a Bridge? Chicago Edition I (April 18, 2013)
What is a Bridge? Chicago Edition II (February 1, 2020)
What is a Bridge? Bethlehem Edition I (July 1, 2020)
What is a Bridge? Bethlehem Edition II (July 15, 2020)