# "Roads" vs. bridges - the philosophical perspective



## wdw35 (Dec 12, 2008)

I started this thread after seeing a few phrases in the Albanian motorway forum:

http://www.skyscrapercity.com/showthread.php?t=494988&page=70

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"27 works of art"
I suppose they mean 27 complicated bridges which are going to be state-of-the-art.

No, there is a similar wording in French about bridges and things like that. They say "ouvrage d'art", which basically means structure.

The same term is used in Romanian: "lucrare de arta" (work of art) in reference to structures.
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Engineeringly (is there such a word in English?) speaking, there are two approaches towards the road / bridge dichotomy.

The first approach is that of "road" engineers. They see the natural state of the road as being "on the ground" (i.e. road placed on a roadbed placed on the ground), while bridges are regarded as "accidents" / "mistakes" within the roadbed continuum. Also, they argue that maintaing a structure is a much more difficult thing to do, as it implies entirely closing down the road on this segment and conducting consolidation works for weeks (if not months) to bring it back into shape.

The second approach is that of "bridge" engineers. They see the "normal" roadbed as trite, boring and simple, and believe that the natural condition of the Road is for it to be on a structure. Simple and pure, and independent of the capricious conditions of the ground.
As such, they call structures "works of art": "ouvrage d'art" in French, "lucrari de arta" (works of art) in Romanian and so on.
Indeed, they say, there is a much more artistic touch involved in conceiving, designing and building a structure as compared to the boring cut and fill approach suited for the "non-structure" condition of the road.

This may have something to do with the naming of specific higher education programs in various countries. Here in Romania we say "Facultatea de Drumuri si Poduri" (the University of Roads and Bridges) or "Directia Regionala de Drumuri si Poduri" (the Regional Directorate of Roads and Bridges). Others choose to say, e.g., only "Road Engineering" (as opposed to "Roads and Bridges Engineering").

So what is your take on this dialectic?

Edit: here in Romania we seem to be leaning towards the latter approach in motorway construction:

http://www.autostradatransilvania.r...de Barcau viaduct (km 7+570)-general view.jpg

http://www.autostradatransilvania.r...load=1&Name=5b_km 13+222 U-beam launching.jpg


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## J N Winkler (May 14, 2007)

wdw35 said:


> "27 works of art"
> 
> I suppose they mean 27 complicated bridges which are going to be state-of-the-art.
> 
> ...


The phrase "27 works of art" is really an example of a false friend in operation, because a native speaker of English would say "structures," which is indeed a general term encompassing bridges, viaducts, tunnels, retaining walls, gabions, dams, barrages, jetties, etc.

French and Romanian are far from alone in having a phrase for _structure_ which is some variant on a literal translation of "work of art." Dutch (_kunstwerk_), Portuguese (_obra de arte_), and Italian (_opera dell'arte_?--my memory is uncertain) have such expressions too. But I personally prefer the German term, _Ingenieurbauwerk_, which literally translates "engineered building work," because it gives a better idea of the nature and purpose of a structure--i.e., an object with vertical extent which is designed to take certain defined loads. The art being talked about in "work of art" phrases for structures is engineering statics, not the kind of art that is interpreted in museums or galleries.



> The first approach is that of "road" engineers. They see the natural state of the road as being "on the ground" (i.e. road placed on a roadbed placed on the ground), while bridges are regarded as "accidents" / "mistakes" within the roadbed continuum. Also, they argue that maintaing a structure is a much more difficult thing to do, as it implies entirely closing down the road on this segment and conducting consolidation works for weeks (if not months) to bring it back into shape.


Not really. What engineers of any description, whether road or bridge, are after is fitness for purpose. There are many ways to rehabilitate, improve, and even widen a modern bridge without closing the road altogether, so for first construction in rural areas the choice between a structure and road pavement ultimately comes down to hydrology and economics. At the mundane level, such as minor stream crossings and the like, the choice is often between a bridge, which requires careful levelling during construction and frequent maintenance thereafter, and a culvert, which is almost maintenance-free but has less capacity to handle floods.

At a more advanced level, such as choosing a suitable alignment for a motorway in the mountains, there is often a tradeoff between building to a high design speed with frequent tunnels or building to a lower design speed with cuts and sharp curves instead of tunnels. The factors that are considered include the extremely high costs of building a tunnel and maintaining it thereafter, set against the higher benefits to traffic of being able to cross a difficult mountain range at 120 km/h (or thereabouts) rather than the design speeds of 70 km/h or even slower which are sometimes adopted for motorway-type roads in mountainous terrain.

Decisions of this type are generally made at the planning level, when the function and characteristics of the projected road are identified, so roadway and bridge engineers are really not in the position of representing contending philosophies of design. The focus of the engineers is generally on developing consensus in favor of solutions which are both economic and effective.



> The second approach is that of "bridge" engineers. They see the "normal" roadbed as trite, boring and simple, and believe that the natural condition of the Road is for it to be on a structure. Simple and pure, and independent of the capricious conditions of the ground.


Not really. Bridge engineers are very aware of the costs of the structures they build. On a square-foot basis, bridges are far more expensive than roads, and tunnels are even more expensive than bridges. Structures in general require more effort in design and construction supervision, and are more susceptible to catastrophic failure when loaded beyond their design limits. Any structural engineer worth his salt will have plenty of respect for roadway engineers because he knows that, with appropriate drainage and compaction of the subgrade, what they are designing is extremely robust compared to a bridge.



> As such, they call structures "works of art": "ouvrage d'art" in French, "lucrari de arta" (works of art) in Romanian and so on.
> 
> Indeed, they say, there is a much more artistic touch involved in conceiving, designing and building a structure as compared to the boring cut and fill approach suited for the "non-structure" condition of the road.


No, no, no, not true. What roadway engineers do is alignment design. That is very easy to do badly and very difficult to do well. If you are interested in good alignment design, you have to coordinate horizontal and vertical curves carefully and you have to do perspective checking in critical areas to be sure that what the driver sees is always a smooth paved ribbon in harmony with the landscape (i.e., no curves which conform with the standards but look like kinks or bends when viewed from far away).

Because of alignment design, the tasks roadway and bridge engineers face are approximately equal in difficulty. In order to develop a reasonably well-optimized alignment, location studies have to be done, data regarding elevations and soil types has to be gathered, and tentative alignments need to be checked using a DTM and visualization software (models and perspective drawings were often used before highway design was computerized). It is true that the choice of pavement type is comparatively easy for roadway engineers--it is mostly a matter of referring to a standard pavement design catalogue--but by that point more than 90% of the hard work has already been done. In comparison, bridge engineers have to do a lot of mathematically intensive work comparatively late in the design process, but when the project is in final design, they are already able to work with the agreed alignment. Some aspects of bridge design, particularly minor road crossings in unmined terrain, are straightforward enough to be routinized.



> This may have something to do with the naming of specific higher education programs in various countries. Here in Romania we say "Facultatea de Drumuri si Poduri" (the University of Roads and Bridges) or "Directia Regionala de Drumuri si Poduri" (the Regional Directorate of Roads and Bridges). Others choose to say, e.g., only "Road Engineering" (as opposed to "Roads and Bridges Engineering").


I don't think it means much one way or the other. Roadway and bridge design are separated in design offices everywhere, but this is mainly because the task mixes are so different that they have to be considered subspecialties. They, however, are both aspects of civil engineering, and in the US you need to have a bachelor's degree in civil engineering in order to work for a state DOT in an engineering capacity, whether as a road or bridge engineer.

In France, if you are interested in highway design, the school for you is the École National des Ponts et Chaussées (ENPC) but, if you graduate and go to work with the centrally maintained road system, you will probably be assigned to one of the eleven Directions interdépartementales des Routes.

Keep in mind also that as a road network matures, the activity mix changes, since the focus shifts to upkeep rather than primary construction. In primary construction (generally on new location), the roadway and bridge engineers are in the driver's seat, because they define over 90% of the construction activity. When an already-existing road is being rehabilitated, the most important person in the design process is the person who devises the traffic management plans.

So, traffic engineers rule.


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## ChrisZwolle (May 7, 2006)

> So, traffic engineers rule.


Isn't this more part of the civil engineering? I mean the design of the bridges themselves. I know the field of traffic engineering is pretty wide (I never work in the technical design for instance), and also coincides with civil engineering.


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## J N Winkler (May 14, 2007)

Traffic engineering is on the edge. The core of civil engineering is loads and stresses on physical objects, while the focus of traffic engineering is adaptation of infrastructure to accommodate certain empirical regularities derived from large-scale observation of human behavior. It can be argued that traffic engineering does not mobilize the same skill sets as road and bridge engineering, which fall more clearly within the traditional domain of civil engineering.

AIUI, in most American university degree programs in civil engineering, traffic engineering (or, as it is often called, transportation engineering) does not appear until comparatively late, as a bolt-on elective. In some countries, e.g. the UK, you can get a job doing traffic design (including drawings and schedule sheets for signing and marking) without any training in civil engineering or, for that matter, formal education beyond age 18. (I am not sure if school-leavers can be accepted as trainee traffic designers though--in the UK school-leaving age is 16.) Some US states, including Oregon, have independent traffic engineer qualifications which are designed to allow traffic engineers to seal construction plans for certain types of signing work without needing to have a full-blown civil PE license. Meanwhile, some state DOTs like Caltrans won't accept traffic work on the primary state highway system unless it has been sealed by a civil PE.

Traffic engineering attracts a lot of people who have started out doing something other than civil engineering and thus have no BSCE or civil PE license. As a result, there is a lot of confusion (especially in the US) about whether traffic engineers should be trained, licensed, and held professionally responsible in the same way as traditional civil engineers. What this means is that, in order to be considered a high-flyer in the traffic engineering profession, you need a BSCE, a civil PE license, and a PTOE qualification.

In the UK the (loose) equivalent of a US/Canadian PE is a chartered engineer. I have heard stories of chartered engineers with extensive civil design experience running into trouble in traffic design contexts because they simply couldn't get accustomed to things like sign design standards.


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