3097: Bridge Types

2025-07-03T16:18:47Z

2A02:AB88:7815:7E80:2AC:AB46:70B2:F9A8: /* Explanation */ Einstein–Rosen bridge

{{comic
| number = 3097
| date = June 2, 2025
| title = Bridge Types
| image = bridge_types_2x.png
| imagesize = 740x581px
| noexpand = true
| titletext = Pontoon bridges are just linear open-sided waterbeds.
}}

==Explanation==
{{incomplete|This page was recently created by a TESSERACT BRIDGE ABUTMENT. Don't remove this notice too soon.}}
This comic shows, in a four-by-four grid of images, a series of bridge types. As with [[1714: Volcano Types]] and [[1874: Geologic Faults]], the comic starts off with real bridge types, and then swiftly proceeds to make things up for absurdity. That said, real-life examples of some of the joke bridges exist, as shown in the table below. The joke lies in the progression of bridge types from the simple and straightforward to the complex and ridiculous.

{| class="wikitable sortable"
! Name given
! style="width:7em;"| Status
! Type
! Explanation
|-
! Plank
| {{Yes|Real}}
|{{w|Beam bridge}}
|A straightforward piece of solid material (in this case, made of solid wood, but there are {{w|Clapper bridge|other materials}}) is the most basic form of bridge, and generally the easiest to construct, but also the weakest. Consequently, such bridges are only suitable for small spans and light weights (such as a footbridge over a stream).
|-
! Rope
| {{Yes|Real}}
|{{w|Simple suspension bridge}}
|Rope bridges consist of several lengths of rope anchored on both sides of the span. Typically, one or more ropes will be intended to support the crossing load (possibly with boards or some other walkway between them), and additional ropes will act as handrails, reducing the risk of falling. These are typically only intended for foot traffic, due to their light construction and lack of rigidity. Because of the simple materials and relative ease of construction, they're often used as improvised bridges. However, a ridiculous design for this bridge type was explored in [[3048: Suspension Bridge]], in which the rope functions as a road.
|-
! Truss
| {{Yes|Real}}
|{{w|Truss bridge}}
|A truss is a common type of framework consisting of supports connected in a series of triangles which provide support for a load. This design provides significant strength and rigidity with minimal material and weight. A truss bridge can either have the truss above the bridge platform (as in the drawing) or underneath it (also known as a deck truss). This is the first bridge type on this list which is commonly used for vehicle traffic.
|-
! Trestle
| {{Yes|Real}}
|{{w|Trestle bridge}}
|A trestle bridge is held up by supports reaching all the way to the ground beneath. Typically at least some of the supports will slope outward to give a larger base of support. Once common for railroads, these are less popular nowadays, but are still seen in certain areas and applications.
|-
! Arch
| {{Yes|Real}}
|{{w|Arch bridge}}
|Arches are one of the oldest kinds of bridges for carrying significant loads. They can be made out of rock or metal. Each span consists of an arch resting on supports. Simple arch bridges rest on both sides of a river or other gap, but longer bridges (as in the drawing) will have intermediate pillars to support multiple arches. The arches distribute the load, allowing a relatively small number of pillar to support weight across the entire deck of the bridge.
|-
! Suspended Arch
| {{Yes|Real}}
|{{w|Through-arch bridge}}, possibly {{w|Tied-arch bridge}}
|A through arch bridge uses a similar concept as an arch bridge, but the deck is entirely or partially suspended below the top of the arch (in this case fully suspended, at the bottom of the arch). The tie of a tied arch bridge refers to using the deck as a tension member to restrain the horizontal spreading of the arch; without a tie, the arch's foundation must resist that horizontal loading. From the picture, it is not clear whether the deck is acting as a tie. Such bridges may use a single arch (as in the drawing) or multiple arches in succession.
|-
! Draw
| {{Yes|Real}}
|Drawbridge (more precisely a fixed-trunnion {{w|Bascule_bridge|bascule bridge}})
|Drawbridges are used to allow ships to pass through obstacles like bridges. They use various methods to raise one or multiple sections of the bridge to create enough height clearance for vessels to pass through, in this case using a cable to rotate the bridge about a pivot point (trunnion).
|-
! Suspension
| {{Yes|Real}}
|{{w|Suspension bridge}}
|A suspension bridge suspends its deck with cables or rods from a cable linked to a pillar and a point a certain distance from each pillar
|-
! Filler
|{{Maybe|Real}} method of maintaining {{w|Grade (slope)|grade}}, not really a 'bridge'
|{{w|Embankment (earthworks)|Embankment}}, {{w|Causeway}} or even a {{w|Dam}}
|Serves the purpose of allowing travel across the gap, but by removing (or {{w|Culvert|mostly removing}}) passage through the gap itself. By filling the gap with hard, irregular material (most commonly rocks), support can be provided, while still allowing water to flow through the gaps. Due to the generally small size of the gaps, generally only slow-flowing water can reliably get through.
|-
! Budget Overrun
| {{Yes|Real}} (with an absurd name)
|{{w|Cable-stayed bridge}}
|Specifically, the pictured bridge is a {{w|cantilever spar cable-stayed bridge}}, similar in appearance to the {{w|Samuel Beckett Bridge}} in Dublin or the {{w|Erasmusbrug}} in Rotterdam. Many bridges in this category suffer severe cost overruns. Randall may be drawing upon his local knowledge of the {{w|Leonard P. Zakim Bunker Hill Memorial Bridge|Zakim Bridge}} in downtown Boston's {{w|Big Dig}}, also strongly associated with cost overruns. Also, while not a bridge, the budget overrun and diagonally inclined tower supporting cables may be a reference to {{w|Montreal Tower}} and {{w|Olympic Stadium (Montreal)|Olympic Stadium}}, which has suffered infamous budget overruns, costing over 6.7 times the initially planned amount.
|-
! Jump
| {{No|Not real}}
|Similar to a pair of small {{w|cantilever bridge}}s, constructed at an incline.
|A "bridge" that appears to be being used by a skateboarder, though in a manner far more dangerous than any jump in a typical skatepark. While not {{w|London Buses route 78#History|normally}} a feature of the highway, jump ramps can be used for gap-crossing stunts by almost any vehicle with sufficient speed. Partial bridges, which allow ''some'' vehicles using them to safely cross the gap, iconically featured in {{w|The Dukes of Hazzard}} TV show, as well as common in various {{w|The Man with the Golden Gun (film)#Car stunts|action}} {{w|Speed (1994 film)#Filming|films}}, though typically less easy to use correctly than the setting implies.
|-
! Halfhearted
|{{Maybe|Not}} real under this name, but with real analogs
|[https://www.archdaily.com/184921/moses-bridge-road-architecten Moses bridge]
|The diagram shows that there was barely any attempt to bridge the gap in the landscape at all, just take the 'deck' down into it and back up out again. The concept may have been inspired, in part, by [https://www.fastcompany.com/90186315/the-strange-art-of-the-melting-bridges-of-google-earth an artifact in Google Earth software].
Structures exist, at the {{w|Fort de Roovere}} in Halsteren, Netherlands and elsewhere, that resemble this 'solution', though these would have involved much thought and commitment in their building, possibly more 'hearted', even, than any more conventional bridge design, especially in the provision of stairs to allow easier ingress/egress (at least for foot traffic) than in the comic's version.
|-
! Waterbed
| {{No|Not a bridge}}
|{{w|Waterbed}}
|Rather than a bridge, it is more like another version of a causeway (see 'Filler') using trapped water to maintain the upper surface.
Named for a 'mattress' type, which is usually a raised surface ''on top of'' a piece of bedframe, with an unusual approach to padding and comfort.
|-
! L'Engle
| {{No|Not real}}
|[https://www.refinery29.com/en-us/2018/03/192728/tesseract-definition-wrinkle-in-time-space-dimension Tesseract AWIT] not {{w|Tesseract|Tesseract (geometry)}} cf. {{w|Einstein–Rosen bridge}}
|References {{w|A Wrinkle In Time}} by Madeleine L'Engle. Characters cross great distances by "tessering", moving via a tesseract through a higher dimension which essentially brings the two ends of the journey together from the perspective of the traveler. The image shows the two ends of the gap being brought together, with the gap apparently crumpled in between them.
|-
! Fun
| {{No|Not real}}
|{{w|Vertical loop}}
|It is a loop-de-loop, not normally a practical or necessary way of bridging a gap. Something previously seen, in an arguably even more impractical manner, in [[2935: Ocean Loop]].
|-
! Repurposed Elevator
|{{Maybe|Real}}, but not as displayed
|Horizontal elevator / {{w|People mover|People mover}}
|There are various implementations of such designs, the best-known one is probably the {{w|Schmid Peoplemover|Schmid Peoplemover}}.
However, unlike a regular people mover, where the door stays upright, the image shows a regular elevator that has been rotated 90 degrees. This not actually its own type of bridge, but just a type of plank bridge where the elevator shaft (or one side of the elevator shaft) is used as a plank - closing the circle to the first image.
|-
! (Title text)
| {{Yes|Real}}
|{{w|Pontoon bridge}}
|Pontoon bridges are described as a series of fictitious "waterbed bridges", as shown above, but constructed without sides. This would mean that that the 'bed'-supporting water flows in one side and out the other, if there is any passage or tidal flow of water. It may technically mean that you cannot cross {{w|The Same River Twice|the same bridge twice}}.
Pontoons rely upon buoyancy, either of the whole deck or distinct floating elements, whereas an enclosed "waterbed" bridge would rely upon the strength of the membrane to keep the mass of water within it, and thus the deck above that mass.
|}

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:Bridge Types

:[A 4x4 matrix of 16 ways to cross the same rectangular hole in the ground]

:Plank [shows a plank laid over the hole]

:Rope [shows a rope bridge with rope guardrail]

:Truss [shows a truss bridge with a triangular truss above the bridge deck]

:Trestle [shows a trestle bridge]

:Arch [shows stone arches supporting a straight deck]

:Suspended Arch [shows a single arch, with the bridge deck suspended from it]

:Draw [shows a truss bridge, with one half opened like an unrealistic draw bridge]

:Suspension [shows the bridge deck suspended from a cable strung between two pillars and the shores]

:Filler [shows the hole filled with dirt and stones]

:Budget Overrun [shows a bridge deck suspended by cables from an artistically shaped pillar]

:Jump [shows two ramps at the edges of the hole, and a skateboarder jumping across the hole]

:Halfhearted [shows a ramp at each side of the hole that leads down to the bottom]

:Waterbed [shows the hole filled with water, two fish and an octopus, a wobbly covering, and two stick figures crossing]

:L'Engle [shows the hole warped such that the opposite shores meet]

:Fun [shows a loop-de-loop rollercoaster bridging the hole, and a skateboarder using it to get across]

:Repurposed Elevator [shows an elevator tower, rotated sideways as a whole, laid across the hole. 2 stick figures using the elevator are also rotated.]

{{comic discussion}}<noinclude>

[[Category:Engineering]]
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Animals]]

explain xkcd - User contributions [en]

3097: Bridge Types