 | Parkways and park roads |  |
LECTURE 1: PREFACE
The geometry of road design begins with an origin and a destination;
this we translate into a direction. It is then through
a series of judgments employing our skills in fitting the ribbon
to lay lightly on the Land that we design the roadway. The simplest
design, of course, is a straight line connecting the origin and the
destination without regard for the topography or for those features
outside of the corridor within which the road is to be constructed.
Instead, we landscape architects strive to describe a line of ever-changing
curvature in locating the road that will preserve the
natural and historic landscape, that will least intrude on animal
habitat, that will lay like a feather on the ground surface, that
opens views to scienic features on the skyline, and that insures
safety for motorists who will use the roadway.
We begin the design with a 314 pencil on study paper over a
topo map. The first line we draw will set the quality for what
follows! It is the reverence we have for the Land and the exaltation
that comes when a beautiful line flows through the pencil that
designs a road! If our hearts don't beat with trepidation at that
moment, we'd do well to put the pencil down. Walk away! The intrusion
onto the Landscape and the consequences of construction are too
devastating to begin poorly.
Once we are inspired by images of that graceful movement over
the Landscape, we are compelled to draw the ribbon. The side of
the pencil leaves broad strokes of graceful curves that fairly
skate along the contours in a joyful melody in the out-of-doors.
That's road design, That's Landscape Architecture!
GLOSSARY:
Park Road - A scenic travel way of everchanging curvature within a
park, designed to lay lightly on land, for the purpose of
visitors' enjoyment of the scenic, natural and cultural features
being preserved and interpreted within or beyond the park
boundaries.
Parkway - An elongated park containing a scenic road connecting two
separated parks, distinguished by the following features:
- The roadway is of everchanging curvature with cuts and fills
kept to a minimum and side slopes are shaped to resemble the
adjacent natural topography.- The roadway lays lightly on the land to impart a sense of
effortless flight through the countryside.- The scenery is enjoyable and unsightly views and noise are
screened by vegetation or topography.- Grade separation structures insure limited access from
adjacent roads.- Indigenous plant species are used to blend the right-of-way
with the native landscape.- Safety is a primary design consideration to reduce accidents
to an absolute minimum.- Medians of varying width may separate roadways having independent
plans-and-profiles.- Vistas and views are directed toward features of interest
beyond the right-of-way.- Billboards are eliminated.
- Design speed increases gradually from the beginning to fit the
topography and decreases toward the end of the roadway.
Tangent - A straight segment of road; the straight line between
P.I.s; the distance between the end of one curve and the beginning
of the next curve (between P.C. and P.C.).
Circular Curve - An arc of constant radius common to two tangents.
Spiral - A curve of gradually decreasing radius beginning at a point
on the tangent and ending at a circular curve (an exception is
P.S.S.).
Transition Curve - A change in direction composed of a spiral, a
circular curve, and another spiral; terms "transition: and
"spiral" are often synonomous.
"P" Line - The line composed of tangents connecting Points of Intersection;
sometimes a Preliminary Location.
Chord - A line connecting the ends of a circular curve, or a vertical
curve, or a tenth-part of a spiral.
Superelevation - The rate of rise of the outside edge of pavement
to compensate for centrifugal force of a moving vehicle.
Assumed Design Speed (from Barnett) - "The maximum approximately
uniform speed that probably will be adopted by the faster group
of drivers but not, necessarily, by the small percentage of
reckless ones." (NOTE! The principal factor affecting the
choice of a design speed is the character of the terrain.)
Compound Curve - A change in direction composed of two or more
differing radii; a feature to be avoided in alignment.
Broken Back - Two circular curves in the same direction connected
by a short tangent.
Vertical Curve - A parabolic curve connecting two vertical tangents;
usually a curve on a profile.
Degree of Curve - The angle subtended by 100 feet of arc.
Radius - The distance from an arc to a common perpendicular point;
the ground distance from a compass point to the curve.
Location - That place on the ground where a road is built.
Alignment - The projected line along which a road is designed or
is built.
Subgrade - The surface on which imported material is to be placed;
the interface between residual soil and the subbase of the road.
Grade - Gradient along the profile; to move soil or material; an
elevation; to manipulate contours on paper; to sculpture the
ground surface.
P.I. - Point of intersection of the main tangents.
P.C. - Point of curvature at the beginning of a circular curve.
P.T. - Point of tangency at the end of a circular curve.
Excavation - The volume of material removed below the original
ground surface.
Embankment - The volume of material deposited on the original ground
surface or above the subgrade.
Borrow - The volume of material imported to account for shrinkage
of excavation.
Profile - The graphic vertical alignment; the line delineating the
existing ground surface.
Plan - The proposed horizontal alignment.
Grade Separation - A bridge separating roadways.
Interchange - A system of roads and ramps connected to a grade
separation structure.
Intersection - An at-grade junction of two or more roads.
AASHO (now AASHTO) - American Association of State Highway (and
Transportation) Officials.
THOUGHTS ON THE HISTORY OF ROADS
The anthropologists tell us that the human species originated
in the savannahs of Africa, a landscape netted with animal trails
connecting watering places to grazing places to nesting places. As
the lower waterholes dried up each year, the herds moved to higher
ground—and the early people followed as nomads on the migration trails.
When the early people invented The Wheel—and when they domesticated
The Horse—I do not know. But when they placed their burdens
on an axle between two wheels to be drawn by a horse, the trails
became two parallel tracks across The Land. We do know that the
people of the Middle East built a system of roads over the trade
routes and that the Greeks extended their military power over much
of that known world. It was the system of chariot roads that bound
together the Empire under Rome from the British Isles to the Holy Land.
The Horse, remember, had occupied much of North America before
the Ice Age—and disappeared before the first humans crossed the
narrow bridge of ice from Asia. The American Indian waited for the
Spanish Horse for over thirty thousand years if our interpretation
is reasonable. The Spanish carved a net of roads from Central
America to Florida and California and north to the Rockies and Plains.
What early Indian became the first Horseman able at last to pursue
the buffalo? and to fashion a teepee and travois to mark the American
Landscape along the buffalo trail?
The French, in their quest for furs, pushed upstream from the
St. Lawrence to Great Lakes to the Upper Mississippi and Missouri
and then downstream to the Gulf. They were voyageurs rather than
builders of roads. An American historian compared the early Europeans:
"The Spanish came for gold; the French came for furs; the
English came to stay." And so it was left to the English to build
the Kings Highway and Post Roads and to settle the Tidewater of the
Eastern Seaboard. The science of canal building was borrowed from
Europe to extend commerce and settlement above The Fall Line to
cross the Piedmont and thereby secure the British settlement against
the French who extended their influence into the Ohio.
It was the system of land grants and patterns of settlement that
followed the great rivers that caused roads in the East to become
of surveys that caused roads west of the Appalachians to follow
straight lines rather than meandering routes.
Westward Expansion into the Northwest Territory required roads
and canals to cross the mountains. The National Road was started
from Baltimore and the Erie and C & O Canals were started from
Albany and Washington to reach the newly acquired lands. And in an
accident of time, the steam locomotive arrived to challenge the
freight wagon and canal barge.
The Horse pulled the wagons across the Western Plains and The
Rockies before the railroads met at Golden Spike in Utah. A system
of roads had been built westward to supply the Army forts along the
Oregon and the Mormon and Sante Fe Trails. Railroads were extended
to parallel the early roads and in some places were built over the
towpaths of the early canals.
The Civil Engineer had made the canals and railroads his realm
while he computed the excavation for waterways and tunnels, the gradient
for lift locks, and the curvature for steel tracks. He developed
tables for faster calculations and for uniformity of standards for
construction. He refined transition curves and superelevation of
tracks to provide a smoother ride and reduce maintenance of rolling
stock hauling the coal from the Appalachians to the cities and
factories of the East in a change from water-driven machines to steam
power.
Meanwhile, The Horse did what he'd done for decades: he worked
the farm, trotted the family to town, and was the pride of the avenue
and racetrack. Several of the Eastern States, in an effort "to get
the farmer out of the mud", built a system of farm-to-market roads.
Until 1918, remember, most Americans lived on farms, dependent on
The Horse for their livelihood whether they sold or consumed the
product of their labors. The hard-surfaced roads enabled The Horse
to draw heavier loads than he could drag through the mud—and he
could pull a car over steel rails even easier.
The bicycle flourished on the new hard surfaced roads, especially
after Mr. Firestone and other inventors discovered a way to make a
rubber tire to soften the ride and reduce the noise on the streets.
Henry Ford didn't invent the motor car—but he did introduce
methods which led to mass production of the machine at a cost many
Americans could afford. The farm-to-market roads were overtaken by
the motor car; then a box was placed over the rear axle and the
American farmer acquired a Truck! I don't know when the Ford Tractor
appeared on the family farm—but it was the farm-to-market road, the
motor car, and the tractor that caused the decline of Americans' love
affair with The Horse. In 1916 the first Federal Aid for Highways
Act was passed by the Congress to provide a nationwide system of
roadways for motor cars. The Horse has served Americans from the
1500s—over four hundred years!
Frederick Law Olmsted had designed the carriage roads of our
Country's great city parks before America was off and running into
the Age of the Automobile. He had designed bridges to separate
carriage traffic, and roads of ever-changing curvature for pleasure
in a rural landscape before the Civil Engineers switched their attention
from railroads to roadways. The partnership of Gilmore Clark,
Landscape Architect, and Jay Downer, Civil Engineer, led to the
interdisciplinary design of the Bronx River Parkway in 1922 and
the system of parkways in Westchester County.
Tommy Vint authored the interbureau agreement in 1926 which
provided for the design of park roads within the National Park
System to be done by Landscape Architects of the National Park
Service working with Civil Engineers of the Bureau of Public Roads.
Out of that agreement came the Blue Ridge Parkway, and then Skyline
Drive and Colonial Parkway; Stan Abbott and Ed Abbuel, Landscape
Architects of the Park Service worked with Engineers of the Bureau
of Public Roads during those years of the early 1930s.
The high-speed Autobahns built as defense highways in Germany
during the 30s so impressed General Eisenhower that he urged Congress
to authorize the 46,000 mile Interstate System in 1956. Until the
1950s when Detroit reached record auto production, the railroads
had been the primary carriers of freight and passengers. Long distance
bus travel and rapid truck deliveries over Interstate Highways
caused the railroads to decline; the failure of the railroads to
restore pre-World WarII passenger service and the abundance of low-cost
private automobile.
The Interstate Highway System was indeed influenced by the
successful features of the Parkways designed by Landscape Architects
and Highway Engineers. The Palisades, Taconic and Merritt Parkways
were limited-access roadways. The Parkways built in the Washington
area (Suitland to Andrews AFB, Baltimore-Washington to Fort Meade,
and George Washington Memorial Parkway to CIA Langley) were designed
by NPS Landscape Architects working with Highway Engineers of The
Bureau under the 1926 agreement authored by Tommy Vint. The American
Society of Landscape Architects elected Jay Downer and Frederick
Cron, two top-notch Highway Engineers, to Honorary Membership in the
Society. (Joseph Barnett, I have read, was also an honorary member.)
The State Highway Officials organized to lay out a national code
of uniform traffic controls and safety practices which proved to be
effective during the construction of the Interstate System. Funds
amounting to 90% of construction costs were allocated to the States
to design and build those segments of the System within their jurisdictions.
The Bureau of Public Roads was reorganized to become the
Federal Highway Administration in the Department of Commerce to
administer the funds allocated to the States and to insure compliance
with the guidelines laid down by AASHO.
The displacement and relocation of neighborhoods and families,
the accelerated rates of run-off, and the increased hazards of
water and air pollution due to highway construction became public
concerns. The Highway Beautification Act of 1965, the National
Highway Safety Act of 1966, and the National Environmental Policy
Act of 1969 were expressions of public opposition to the effects
brought about by the Interstate System. Signboards and visual
encroachments were regulated, roadside hazards were reduced, the
National Highway Safety Council was established, and environmental
impact statements were required. The luxury automobile, mile-a-minute
travel time, and the monotony of constant high speeds over
extended distances had arrived.
In 1972 the whole scheme suddenly stopped by what we now call
"The Fuel Crisis." The earlier prophesies by the scientists were
The economic power of the world shifted to the oil producing
countries—and the results were restrictions in the gasoline
supply, reduction of travel speeds at 55 MPH, and the redesign of
the automobile to increase fuel economy.
THE FUTURE:
Is the high speed freeway obsolete? What effects will rapid
transit have on our urban centers? How will space technology change
our concepts of travel? What are the alternatives in terms of fuels?
Will the helicopter become a common family vehicle? What is the
potential of the air-cushion vehicle? What are the substitutes for
the automobile? Can we produce alcohol from wood or corn in quantities
to replace oil?
COMPARISON OF PRIORITIES:
In 1972, the Year of the Fuel Crisis, 56,600 Americans were
killed on the highways. Today the rate is about 46,000, a reduction
brought about by the 55 MPH enforced speed limit, and other safety
improvements. The combat deaths during the War in VietNam were
about 46,600; training accidents, sickness and other causes boosted
that total to 56,600—ironically the same as our 1972 highway
fatalities.
Can we Landscape Architects help in saving American lives?
I believe we can.
| Parkways and park roads | |