All Roads Lead To Rome: Ancient Roman
David Geoffrey Smith, P.E., P.L.S.
While the Scanner typically features articles about modern
breakthroughs and futuristic marvels of highway engineering
and technology, it is also always interesting to look toward
the past for inspiration and to recognize the vision and ingenuity
of our forebears.
According to family history, one of my ancestors living over
1,600 years ago was a fellow named Flavius Afranius Sygarius,
The Wild Boar. At the culmination of a lengthy political
career he was appointed to serve as Consul to Lyons in Roman
Gaul by Emperor Gratian in 382 AD. It is amazing to consider
the state of highway engineering during the days when he looked
upon the landscape. It has been said that one key to the success
of the ancient Roman Empire was its efficient highways. The
Roman highway system allowed speedy movement of troops, trade
caravans, diplomats, and couriers; enabled rapid expansion of
the Roman sphere of influence; offered military protection from
barbarians and other invaders to local governors; allowed farflung
outposts to stay in close contact and communication with the
centers of government; allowed citizens to prosper through trade;
and a host of other benefits.
Ancient Romans had highway administration systems similar to
our Federal Highway Administration and state Departments of
Transportation. Like our modern highways, Roman roads likewise
had different levels of classification in terms of usage, maintenance
and funding. These classifications in order of priority from
highest to lowest were:
- viae publicae (major public roads, funded by the Empire),
- viae militarus (military roads, with the army as responsible
- actus (local/regional roads, primarily funded and administered
by the local Governor), and
- privatae (privately funded roads).
earliest and most well known of these Roman highways is the
Via Appia, or Appian Way, running from Rome to the Bay of Naples,
constructed around 300 BC. Like modern highways, ancient Roman
roads like Via Appia, Strata Montana, Via Aurelia and others
made up a vast network of highways and local roads. The network
was extremely well coordinated and extensive. At the height
of the Roman Empire, with use of sea ferries, Sygarius could
have traveled continuously on Roman highways from the northwestern
limit of the Empire at the Antonine Wall in northern Britain,
across the Channel to France, through his city of Lyons, and
then onward to Rome, Byzantium, Antioch, eventually ended his
journey in Jerusalem at the southeastern extent for a distance
of over 4,070 Roman miles, or approximately 3,740 U.S. miles
(see table 1). Naturally, as the center of power, Rome was the
hub of it all. As they say, All Roads Lead To Rome.
Roman surveyors were extremely skilled and could lay out accurate
curves, Roman roadways typically are linear. This was due to
the use of sighting techniques, which naturally resulted in
very long tangents. This is most noticeable in the fact that
Roman roads make most of their key turns and deflections on
high ground where sighting was most easily facilitated. Road
segments would often be laid out with series of hundreds of
sighting points and beacons.
Before electronic traffic counters and modern concepts of axle
loadings, the Roman highway engineer would use his years of
e m p i r i c a l observations of local custom and traffic,
as well as knowledge of local soils and geology to determine
the ideal roadway section.
There was no mandated typical section in Roman highways, however
the majority were constructed on an earthen embankment, called
an agger, which would provide a welldrained base. On important
routes, this agger could be constructed as high as 6 feet above
the surrounding terrain, and 40 to 50 feet in width. This agger
would typically be constructed of locally excavated earth and
stony rubble, called statumen, and placed directly on level
ground or within an excavated trench or then built up.
Material for the agger would often come from scoop ditches,
excavated to either side of the proposed embankment, which would
also aid in intercepting stormwater and for providing drainage.
Scoop ditches were on occasion so extensive that they were in
fact quarry pits providing roadway stone.
Upon this embankment, the agger, would be constructed a middle
layer of finer material, called the rudus, which would be rammed
down and compacted. Upper layers would be laid very carefully
to maximize compaction. The middle layer would often contain
sand and similar fines. The uppermost layer would be the metalling,
a wearing surface, typically paving stones, as locally available
within a few miles. At a bare minimum this would consist of
gravel, however often cobblestone pavers or stone slabs would
be used. This finished grade would also typically feature stone
curbs, to contain the paving stones and delineate the edges
of the road. If interesting local materials were available,
for example burnt lime or volcanic tufa, they would also be
used to provide concrete-like wearing surfaces. In areas where
there was an iron working facility, iron slag left over from
manufacture would be incorporated into the upper course to provide
an incredibly hard wearing surface.
Roman highways would typically be cambered for drainage, and
would sometimes have intentional wheel ruts gouged into them
to aid carts and wagons on potentially difficult stretches of
road given rain-slick or icy conditions. Similarly, there were
occasional grooves perpendicular to the roadway scored into
the road to prevent horses from slipping.
Decrees by Augustus and others provided for roads varying in
width dependent upon importance and function. The widest, most
important roads, decumanus maximus, were approximately 40 feet
wide, whereas country roads were often 20 feet wide, to allow
passing or two lanes of travel in opposing directions. Minor
roads were typically around 8 feet wide.
Roman highways also had a right-of-way or easement
of sorts, which were strips of land to either side of the agger
embankment and main drainage ditches, typically kept clear,
where cultivation and building were forbidden. These clear zones
may have served multiple functions, such as to prevent assault
by unfriendly forces or highwaymen, or to provide an area for
roadside grazing. Small, shallow ditches called boundary ditches
served no apparent drainage function, instead typically delineated
these clear zones. In Roman Britain, many of the major roads
had a clear zone 84 feet wide, whereas smaller country roads
had a clear zone of 62 feet.
Roadways were well signed and marked at every mile with a stone
monument, of tremendous accuracy. Ancient Romans utilized a
form of odometer, essentially a calibrated, geared mechanism
attached to the wheel of a cart for measuring distances and
setting mile markers. Mile markers were often monumental in
themselves, many standing 6 feet tall, and bearing mileages
to the next town and intermediate points, as well as dates and
names of the builders.
Amazingly, many sections of the ancient Roman roads, like Via
Appia and die Bergstraße are still to this day intact
in one form or another, even after 2000 years of use, weather,
neglect, political upheaval and other circumstances that often
ruin a nations infrastructure. These ancient Roman highways
were unparalleled in their design and construction until the
19th century. To place it all in a proper context and perspective,
perhaps the lesson to learn is that even with 2000 years of
technological advances such as aerial photography, GPS and laser-guided
graders, there is still no substitute for vision, experience,
and ingenuity in highway design.
Dave Smith is a Professional Engineer and Professional Land
Surveyor specializing in highway design, GIS, surveying and
mapping, and custom engineering and CADD software development.
Over the past 18 years, Mr. Smith has been involved in a wide
variety of surveying and engineering projects up and down the
East Coast, from Delaware to Vermont. In addition to surveying
and engineering, he has a wide variety of eclectic outside interests,
such as history and archaeology. He is Past President of the
North-East Penn Section of ASHE, and recently developed a website
for the North-East Penn Section (http://www.ashenepenn.org/).
For further information, his email is email@example.com.
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