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The Transitway / mall : a transportation project in the Central Business District of metropolitan Denver

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Title:
The Transitway / mall : a transportation project in the Central Business District of metropolitan Denver
Creator:
I.M. Pei and Partners, Architects and Planners
Place of Publication:
Denver, CO
Publisher:
Regional Transportation District
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
16th Street Mall
Public transit
City planning
Spatial Coverage:
Denver -- 16th Street Mall

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Auraria Library
Holding Location:
Auraria Library
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Copyright [name of copyright holder or Creator or Publisher as appropriate]. Permission granted to University of Colorado Denver to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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Full Text
THE TRANSITWAY/MALL
A Transportation Project
in the Central Business District
of Metropolitan Denver
f
Prepared for the Regional Transportation District
Denver, Colorado
I. M. Pei & Partners, Architects and Planners
November 1977


CONTENTS
Summary
Design Concept
Objectives and Constraints
Transitway / Mall Plan
Pian Elements
Paving
Planting
lighting
Street Furniture
Transit Vehicle
Functional Requirements
Traffic Circulation
Service and Emergency Access
Utilities and Vaults
Transfer Facilities
Civic Center
Skyline


SUMMARY
The Transitway/Mall is a major transportation project in the central
business district of metropolitan Denver. Its goals are threefold:
1. To lessen traffic congestion in the downtown;
2. To provide more efficient bus service to city and suburban
neighborhoods; and,
3. To create a new pedestrian environment in the downtown
a place for people.
The project will transform 16th Street between Broadway and Larimer
into a tree-lined pedestrian precinct. Electric shuttle cars the only
vehicles allowed on the mall will carry passengers to and from trans-
portation transfer facilities located at each end. Express commuter
buses will enter the transfer facilities at below-street concourses where
riders will transfer to transitway vehicles waiting at ground level.
Shuttles will leave the terminals every 70 seconds stopping at each block
along 16th Street.
i
By intercepting express buses at the edges of the retail-office core,
there will be fewer buses on downtown streets and therefore sub-
stantially less traffic congestion. Also commuter buses will be able to
get in and out of downtown much faster enabling them to make additional
productive trips during rush hour.
Basic elements of the 16th Street urban design concept include:
. A double row of mature Honey Locust trees flanking a 22-foot wide
promenade in the center of the street.
. Two 10-foot wide transitway paths on either side of the central zone.
. Widened sidewalks along the storefronts.
. Patterned paving over the entire street surface in varying tones
of muted grays and red.
. A combination light fixture creating a variety of lighting levels at
dusk, during the evening, and for late-night security.
. Shelters, benches, fountains as well as places for displays,
sidewalk cafe's, and special events.
This basic arrangement is modified on the end blocks of the mall. Here,
the transitway paths come together and are flanked by a single row of
trees offset to open the street to views of the mountains and the D & F
Tower at one end, and the Capitol dome at the other.


/



DESIGN CONCEPT
Great cities of the world, large and small, are known and remembered
for the quality of their urban spaces. The Transitway/Mall affords the
opportunity to create a memorable urban space in the City of Denver
while, concurrently, making the downtown more accessible to the entire
region. The means a concept of two transportation nodes linked by a
transit mall is a significant urban planning innovation.
Objectives and Constraints
The street design involves three disparate aspects: functional, environ-
mental and formal. It must solve functional problems such as utility
access, sidewalk vaults, traffic circulation, building service, emer-
gency access, pedestrian movement, and public transportation. It
must respond to environmental concerns including sun, wind, rain,
noise and air quality. It must also make.formal, qualitative judge-
ments about scale and imageability, and deal with relationships to the
existing urban fabric the buildings that line the street and the views
and vistas at either end.

Sixteenth Street is narrow (exactly 80 feet). Moreover, it is embel-
lished by rather assertive projections from building faces such as
awnings, canopies, marquees, signs and graphics. The result is
a street of almost intimate scale with a great deal of extant interest
and variety along it.
Kecent American malls have tended to be highly episodic and decora-
tive, almost like amusement parks. In our judgement, 16th Street
does not need a series of new episodes but rather, a complement to the
diversity that now exists. In short, the challenge of the design concept
is to create a unifying theme and common identity for the street while
protecting its distinctive personality.
Typical Existing Block
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Transitway/Mall Plan
The design process started with the issue of landscape. One can argue
against trees on a mall. After all, some of Europe's most handsome
and successful urban plazas and pedestrian streets consist only of
paving, bollards and benches. In Denver and on 16th Street, however,
we must emphatically argue for the tree. Environmentally, it will
provide protection from wind, sun and rain. Formally, it is the best
means to create the unifying theme for which the street cries out.
The location of trees is crucial. Placed too close to the structures,
they will block visibility and accessibility to shops, and obscure the
image of the street wall. The place for trees is at the center. The
plan proposes an offset double row spaced diagonally 32 feet apart,
flanking a pedestrian promenade 22 feet wide.
On either side of this central zone are two 10-foot wide transit pathways.
These vehicle lanes are slightly depressed and are paved with the same
material as the remainder of the mall. The objective is to define the
vehicle paths for safety in the least obtrusive way. At the edges, the
existing sidewalk spaces are widened from 15 to 19 feet.
The resulting cross-section yields several functional benefits. Existing
utility lines generally stay clear of the center of the street (where trol-
ley tracks once ran) so the tree roots will avoid utilities. A crumbling
collection of vaults that exists under about half the present sidewalks
can be rebuilt or phased out incrementally since the two major mall
elements transit paths and trees can be installed independently.
The center of the mall can be thought of as a dilation zone of new public
open space as opposed to sidewalk areas which are more quasi-private
spaces adjuncts to the shop themselves. The plan provides a full
complement of new lighting, benches, fountains, shelters and other
amenities. But here we have stopped, for the plan by choice is a simple
one. It is a framework and setting for both the present and future. Fill-
ing it initially with an array of podia, playgrounds or other fixed objects
would preempt opportunities for creating new things later on. Ample
space is provided for sidewalk cafds, kiosks, vending carts and dis-
plays which can evolve into permanent elements or change as different
needs emerge.
Typical Proposed Block


End Blocks
Looking at the 11-blocks between Broadway and Larimer Street, one
senses three distinctive zones. The middle is a dense strictured. canyon
of urban buildings. The western end opens to the grandeur, of the Rockies
punctuated by the D & F Tower. The opposing end offers a tantalizing
glimpse of the Capitol dome and rotunda.
The design is organized to reinforce the separate identities of these
three zones. At Curtis Street, the transit paths come together on the
mall's north side and are bordered by a single row of trees for the three
blocks to the Skyline transfer facility. At Tremont Place, the paths re-
join on the south side and, similarly, are bordered by a single tree line
for the two remaining blocks to the Civic Center transfer facility.
The result is a feeling of openness at the ends of the street and an
enhancement of their views. The end block plans do not mean a sacri-
fice of greenery, however. It happens on those blocks where many
existing buildings are set back from the right-of-way or where there is
vacant land. These "side spaces" can be landscaped to augment the mall
greenery without diminishing street vistas.




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PLUM ELEMENTS
The essential elements of the mall are paving, planting and lighting.
Done well, these alone will transform 16th Street into a handsome,
memorable pedestrian environment. The following pages illustrate
these elements in detail together with the ancillary street-furniture
components of the plan.
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overleaf: A composite of mall elements on a typical block. The pattern
and color of paving defines and organizes the functions along
the street.




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Paving
As in a room with Persian carpets or intricate parquetry, the qualify of
the floor can set the tone for the whole interior space. The same holds
true for outdoor spaces. More than any single element, the paving
material will establish the character of the mall. For this reason we
have selected a varied and intricate pattern. Its most basic geometry
is a 45-degree diagonal grid responding to 16th Street's 45-degree
juncture with Broadway and the surrounding city street system. Its
design will also encourage diagonal movement within the mall.
But the visually dominant pattern emerges more through a progression
of color, shape and size. We have used three tones: two of gray and a
muted red. It begins along the street wall as a field of gray paving block
which gradually builds in scale as it reaches the center of the mall. The
pattern at the edges is deliberately neutral to avoid competition with the
varied dimensions of storefronts and doorways. In the center zone, the
pattern becomes more colorful and dominant. The adjacent transit paths,
depressed three inches, are clearly delineated by tone and pattern.
Planting
The selection of the honey locust as the appropriate tree for 16th Street
emerged through an analysis of some 72 species evaluated in terms of
several dozen criteria. These included height and diameter, trunk,
branch, leaf and root form, shade characteristics, sun, water and
maintenance needs, disease and insect susceptibility, wind and pollution
tolerance, availability and cost. The list was narrowed to six contend-
ers and several specimens of each already in place in the Denver area
were examined and evaluated more closely.
The honey locust is already familiar bn the streets of downtown Denver.
Its characteristics make it a desirable urban street or mall tree. The
branch and leaf structure is light and lacy. The tree provides shade but
will also create dappled, flickering light on paving surfaces. Its life-
span is long and it is resistant to drought, wind exposure and air
pollution. It thrives in partial shade. It can safely be transplanted in
6-to-7-inch caliper sizes (the trunk diameter measured 12 inches above
the ground) and 20-foot heights. In 5 years it will mature to 10-inch
caliper and 35-foot heights. It requires a moderate amount of water and
minimum maintenance.


Lighting
The lighting concept for the transitway/mall employes a variety of tech-
niques and fixtures for illuminating sidewalks, transit paths, center
zone and intersections.
Foremost is a double row of specially designed 11-foot high pole
luminaires placed along the center zone. These will provide glare con-
trol and correct lighting angles to flatteringly illuminate trees, pedes-
trians and pavement. The fixture, a clear plastic globe with aluminum
reflector and bronze standard, creates several distinctive lighting
effects. The reflectors up-light undersides of trees and illuminate the
center mall beneath. As twilight approaches soft "glitter lights" will
turn on providing a gradual shift from natural to artificial light, and
enhancing mountain views at dusk. Later at night, security lamps
placed on the standards just below the main luminaire globe will be
switched on to light store fronts and pedestrian areas.
Store display lighting will be used to illuminate sidewalk areas, and
street crossings will be lit by waist-high bollards to softly illuminate
pavement areas where trees are absent. Small "runway" lights em-
bedded in the pavement will be placed in the center of the1 transit
vehicle lanes as a guide for the vehicles, a reminder to crossing
pedestrians, and to bring the pavement to life at night.
We recommend that lighting for all cross-street approaches between
16th and 17th Streets be modified to allow a graceful transition to the
new soft ambiance of 16th Street. The existing mercury vapor lumi-
naires should be replaced with lower wattage metal halide sources
placed on existing poles. This will produce better color rendition,
less glare and better visibility at reduced energy consumption levels.
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Street Furniture
In addition to paving, planting and lighting, the plan provides a full com-
plement of street furniture and reorganizes the present array of sidewalk
elements into a more coherent pattern with more uniform design.
BENCHES: Six 9-foot benches are located on each block in the center
zone of the mall.
SHELTERS: A transit vehicle shelter is located at each transit stop at
the near side of each intersection (two per block).
PLANTERS: A series of low, round flower planters are placed along
the mall on each block.
FOUNTAINS: Major fountains are located at Curtis Street and at
Tremont Place, marking the points where the split transit paths rejoin
at the end blocks. As future development takes place along the edges
of the mall, there will be opportunities for introducing additional
water, environmental sculptures and other mall-related amenities.
INTERSECTION BANNERS: A special bronze standard and mast arm
has been designed to hold required traffic control and pedestrian
signals. The standards support a cable for decorative flags and banners
announcing downtown events and marking the approaches to the mall
from side streets.
BIKE RACKS: Racks will be installed close-in on the intersecting
side streets and will be linked to the city bike-way system.
MISCELLANEOUS: Mailboxes and newspaper dispensers are grouped
along the outer edges of sidewalk areas. Metal trash recepticles are
placed throughout the center zone and sidewalk edges.
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Transitway Vehicle
ETD has engaged General Motors to design a battery-powered vehicle
system for the transitway. Its purposes are to collect and distribute
express bus passengers between the two transfer facilities and various
"stops along the mall, to serve as a general mall circulation system,
and to serve passengers from the local bus routes that intersect the
mall at California and Stout Streets.
The vehicle fleet will carry up to 10,000 passengers per hour. During
peak hours, two vehicles will operate in tandem, and in other hours as
single units. Each vehicle can carry 44 passengers and 2 wheelchair
passengers. Throughout the day they will maintain 70-second intervals
in both directions and will travel at a top speed of 15 miles per hour with
an average speed of 7 miles per hour. Stopping at each block, a round-
trip will take 15 minutes on this free-fare shuttle system.
The vehicles are 22 feet long, 8 feet wide and 7.8 feet high. The floor
height is low (12-inch) and doors are wide for short boarding time and
easy entry by the elderly and handicapped. Mall stops and terminals
will have low platforms flush with the vehicle floor. Large glass areas
will provide passengers with views of the mall and will minimize the
impact of the vehicle on the mall visually. The driver-operated vehicles
will run quietly on rubber tires and will be pollution-free. Routine
maintenance and battery change and recharging will take place within the
the Skyline transfer facility.


FUNCTIONAL REQUIREMENTS
Traffic Circulation
The traffic plan for downtown Denver has been the subject of extensive
technical effort. Barton-Aschman and Associates, transportation and
traffic engineering consultants, has worked with an inter-agency task
force comprised of RTD, the Colorado Department of Highways, and
the City and County of Denver to devise a workable traffic plan which
accommodates private automobile movement, maintains overall circula-
tion within the central business district and meets the operational
requirements of the transitway.
The traffic concept provides for the use of 16th Street by transit shuttle
vehicles, pedestrians, and emergency vehicles only, and permits all the
named streets to intersect and cross as at present. Fifteenth Street,
which is now one-way to the southeast will become one-way to the north-
west. Fourteenth Street will also be reversed from its present direc-
tion, and 13th Street will become two-way.
Cleveland Place will be deemphasized and Court Place will be reversed
to provide flow to the northeast. Tremont Place will be reversed to
provide flow to the southwest, and Glenarm Place will become a two-way
street under the traffic plan.
Traffic flow around the Civic Center will occur along East Colfax Avenue,
leading to 15th Street for those travelers headed northwest. For those
moving from the central business district to the east and south, 14th
Street will flow into Bannock, which will become one-way southbound
between Colfax and 14th Avenue, and lead into 14th Avenue eastbound.
Cherokee Street will became one-way northbound.
Through this traffic circulation system, adequate capacity is maintained
for private vehicle movements. Access is also assured to the parking
garages, hotels, and other buildings which require direct service.


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Service and Emergency Access
The servicing of stores and office buildings will continue to take place in
alleys and delivery trucks will be permitted to cross the mall. In those
few cases where alleys are discontinuous, service vehicles will use the
transit path to the nearest named street. Delivery hours will be enforced
to minimize disruption of transit vehicle schedules along the mall, es-
pecially during peak hours.
While construction of the mall is not contingent on alley closures or
revamping of store servicing arrangements, there will be future oppor-
tunities for closing alleys or turning them into pedestrian ways as new
development or renovations take place. It is our hope that at least one
prototype alley closing can be included at the time of mall construction.
For the short term, alleys should be gently lit by sources placed at their
16th Street entrances to alleviate their "black hole" appearance. We
propose a band suspended 14 feet high between buildings to support and to
shield this light source. This will also tend to strengthen the visual
continuity of the building wall along the street.
Ambulances, fire trucks and similar vehicles will utilize the transit
paths for emergency access to buildings on 16th Street. The center zone
of the mall has been kept clear of permanent obstructions and can also
be used in emergencies. This area would become a bypass lane in the
event of a transit vehicle breakdown.
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Utilities and Vaults
Underground 16th Street, predictably, is a twisted maze of sanitary and
storm sewers, water, gas and steam lines, electric ducts, telephone
and street light conduits and other utility paraphernalia in use or long
abandoned. At the street surface are the usual appendages of this system:
.traffic signal poles and control boxes, light standards, catch basins, man-
holes, fire hydrants and assorted valves.
Ideally, mall construction would provide an opportunity to sort out,
reorganize and rebuild utilities into a more efficient and easily accessi-
ble consolidated system. Practically, however, this would be a time
consuming, expensive and very complex process. Our design mandate
was to prepare a mall plan that could be implemented in a short period
without requiring, as a prerequisite, other major 16th Street improve-
ments or expenditures by the public or private sector. Accordingly,
the transitway/mall is designed to be constructed without extensive
utility adjustments.
Existing utility lines generally run in two parallel 16-foot bands adjacent
to existing curbs. The center of the street, where the trees are to be,
is clear of lines that would otherwise have to be relocated to make space
for root balls. Present lines will be accessible from the transit paths
and the outer edges of the widened sidewalks. Manholes will be conceal-
ed beneath specially designed removable lids made of paving block. Fire
hydrants will be shifted slightly, where necessary, to fit neatly with the
paving module. Catch basins will be relocated and augmented as part of
the overall mall drainage system. Utility lines running cross-mall under
alleys and side streets will remain accessible since there will be no
permanent obstructions in their paths.
Perhaps the thorniest problem of the mall is vaults. Under approxi-
mately half the existing sidewalks between Broadway and Larimer is a
collection of underground rooms old, in use or abandoned, struc-
turally sound or fragile. In many cases, their roofs are simply the
concrete sidewalk slab above. Each vault must be investigated in
detail and dealt with separately. Some active ones must be completely
reconstructed and some abandoned ones must be sealed off.
If necessary, this process can take place incrementally. The building
of the mall does not demand the whole job be done at once since no
trees are to be planted there and no transit or emergency vehicles will
run there. The final paving would simply await installation until a
particular vault problem is resolved. Certainly, though, it would be
best to do it all during the initial mall construction period.
We have developed a system for dealing with vaults during construction
of the transitway/mall. Below-grade concrete walls spaced 21 feet apart,
perpendicular to the street, would be built in the vaults from store front
to curb. A temporary store security wall would be constructed across
the front face of each store basement. The concrete walls would then
receive a structural concrete slab upon which the paving would be in-
stalled. At the completion of mall construction, the basement security
wall could be removed to allow re-access to the vault area or, if the
vault is to be abandoned, the wall would be made permanent.


TRANSFER FACILITIES
The success of the transitway/mall depends heavily on an innovative
approach to the transfer facilities located at either end. Two factors
are of particular importance: efficiency and environment.
First, the transfer points will be operationally efficient. Buses will
enter, circulate, unload, load, and leave on precise schedules. Pas-
sengers will transfer between bus and mall vehicle in a direct, clear
line, and mall vehicles will pick up and deliver passengers at an even
rate to keep their scheduled rounds along 16th Street.
Environmentally, these transfer facilities will be much more attractive
than stock bus depots. In fact, they have been designed as new centers
of downtown activity and life that go well beyond their immediate trans-
portation mission. They will provide high, open, skylit public spaces
filled with shops, cascading water, flowers and greenery. They will
employ the latest technology to eliminate noise and fumes. They will
respond to their urban contexts by creating new pedestrian links to tie
the downtown core more tightly together. And, they will include sub-
stantial office, retail and possibly residential uses to augment the
terminals as vibrant downtown focal points.
Civic Center
The Civic Center transfer facility marks the southeastern end of the
transitway and occupies, the block bounded by Broadway, Lincoln,
Colfax and 16th Avenue; It will be used by all express buses from the
southern and eastern urban area. The terminal has three main levels:
a bus concourse, a transit vehicle interchange at Broadway, and an
upper plaza level opening to Lincoln Street. Two mixed-use structures
rise above the terminal complex.


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Transitway Level
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CONCOURSE LEVEL: Buses enter the terminal from 16th Avenue,
ramp down, and circulate about a central pedestrian concourse ringed
with 14 bays. Loaded buses return to ground level and exit either to
16th Avenue eastbound or to Broadway southbound. The pedestrian
areas are screened from buses by sound-absorbing baffles and glass
much like a jet port arrangement where planes are kept hidden from
waiting spaces. Doors will give direct access from the concourse to
the interior of each bus. The concourse, with its high ceiling is
linked to the upper level through a wide central opening containing
escalators and stairs. Auxilliary stairs and elevators for the handi-
capped are provided at either end.
TRANSITWAY LEVEL: Transit vehicles enter the terminal from
16th Street beneath an open double-height, sky-lit roof. Passengers
unload close to the concourse portal, where they escalate down to the
bus level. A suspended electronic display board will inform passen-
gers where their bus is waiting. Small shops and boutiques line one
side of the space and a linear waterfall provides additional animation
apd soft sound. An estimated one-quarter of the bus patrons will
walk from the terminal to their destinations in the downtown.
PLAZA LEVEL: Lincoln Street is approximately eight feet above
Broadway and, accordingly, the design provides an upper plaza which
leads to the State Capitol and surrounding government offices. The
terminal complex will thus provide a new visual and functional link
between 16th Street and the Capitol area.
AIR-RIGHTS DEVELOPMENT: The block is a strategic downtown
site too important to be used only as a terminal. The proposed
mixed-use development will fulfill the site's potential, create a
strong new physical focus in the downtown, and add to the life of the
complex. Two triangular towers rise above the terminal skylight
framing an open vista on axis with 16th Street and opening the mall
to views of the Capitol dome beyond. The towers vary from 10 to 20
floors responding to the sight-line and building height restrictions
that protect views from the State Capitol. All in all, 740, 000 square
feet of usable office space are provided.


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Skyline
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The Skyline transfer facility will be located at the northwestern end
of the transitway. It is here that downtown-bound buses from the north
and west will be intercepted and passengers will transfer to the mall
vehicles. Several potential sites have been investigated and a prototype
for the terminal has been designed.
The functional organization will be similar to that of the Civic Center
transfer facility. Buses will enter and ramp down to a central pedestrian
concourse. Bus bays will be provided, and passengers will move direct-
ly up to the transit way level through a central portal. Mall vehicles will
loop into the terminal to pick up or discharge riders within a high,
naturally lit space lined with retail shops and commuter conveniences.
The Skyline transfer facility will include office or residential uses above
as well, and will create new pedestrian linkages to Larimer Square and
Lower Downtown.
Concourse Level
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Full Text

PAGE 1

THE TRANSITWAY /MALL Transportation Project in the Central Business District of.Metropolitan Denver Prepared for the Regional Transportation District Denver, Colorado I. M. Pei & Partners, Architects and Planners November 1977 ...

PAGE 2

CONTENTS Summary Design Concept Objectives and Constraints Transitway I Mall Plan Plan Elements Paving Planting Lighting Street Furniture Transit Vehicle Functional Requirements Traffic Circulation Service and Emergency Access Utilities and Vaults Transfer Facilities Civic Center Skyline ... 2 4 10 16 20

PAGE 3

... ........... ......... -==-SUMMARY The Transitway/Mall is a major transportation project in the central business district of metropolitan Denver. Its goals are threefold: 1. To lessen traffic congestion in the downtown; 2. To provide more efficient bus service to city and suburban neighborhoods; and, 3. To create a new pedestrian environment in the downtowna place for people. The project Will transform 16th Street between Broadway and Larimer into a tree-lined pedestrian precinct. Electric shuttle cars the only vehicles allowed on the mall -will carry passengers to and from transportation transfer facilities located at each end. Express commuter buses will enter the transfer facilities at below-street concourses where riders will transfer to transitway vehicles waiting at ground level. Shuttles will leave the terminals every 70 seconds stopping at each block along 16th Street. -I By intercepting express buses at the edges of the retail-office core, there will be fewer buses on downtown streets and therefore sub-stantially less traffic congestion. Also commuter buses will be able to get in and out of downtown much faster enabling them to make additional productive trips during rush hour. Basic elements of the 16th Street urban design concept include: A double row or mature Honey Locust trees flanking a 22-foot wide promenade in the center of the street. Two 10-foot wide transitWay paths on either side of the central zone. Widened sidewalks along the storefronts. Patterned paving over the entire street surface in varying tones of muted grays and red, A combination light fixture creating a variety of lighting levels at dusk, during the evening, and for late-night security. Shelters, benches, fountains as well as places for displays, sidewalk cafes, and special events. This basic arrangement is modified on the end blocks of the mall. Here, the transitway paths come together and are flanked by a single row of trees offset to open the street to views of the mountains and the D & F Tower at one end, and the Capitol dome at the other.

PAGE 4

The Transitway/Mall Concept

PAGE 5

,. Existing Block DESIGN CONCEPT Great cities of the world, large and small, are known and remembered for the quality of their urban spaces. The Transitway/Mall affords the opportunity to create a memorable urban space in the City of Denver while, concurrently, making the downtown more accessible to the entire region, The means -a concept of two transportation nodes linked by a transit mall -is a significant urban planning innovation. Objectives and Constraints The street design involves three disparate aspects: functional, environmental and formal. It must solve functional problems such as utility access, sidewalk vaults, traffic circulation, building service, emergency access, pedestrian movement, and public transportation. It must respond to environmental concerns including sun, wind, rain, noise and air quality. It must also make.formal, qualitative judgements about scale and imageability, and deal with relationships to the existing urban fabric -the buildings that line the street and the views and vistas at either end. 1 Sixteenth Street is narrow (exactly SO feet). Moreover, it is embellished by rather assertive projections from building faces such as awnings, canopies, marquees, signs and graphics. The result is a street of almost intimate scale with a great deal of extant interest and variety along it, Recent American malls have tended to be highly episodic and decorative, almost like amusement parks. In our judgement, 16th Street does not need a series of new episodes but rather, a complement to the diversity that now exists. In short, the challenge of the design concept is to create a unifying theme and common identity for the street while protecting its distinctive personality. !:: [, Iii 1:-,' !;;"'": go'

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Typical Proposed Block Transitway /Mall Plan The design process started with the issue of landscape. One can argue against trees on a mall. After all, some of Europe's most handsome and successful urban plazas and pedestrian streets consist only of p;J.ving, bollards and benches. In Denver and on 16th Street, however, we must emphatically argue for the tree. Environmentally, it will ':Provide protection from wind, sun and rain. Formally, it is the best means to create the unifying theme for which the street cries out. The location of trees is crucial. Placed too close to the structures, they will block visibility and accessibility to shops, and obscure the image of the street wall. The place for trees is at the center. The plan proposes an offset double row spaced diagonally 32 feet apart, flanking a pedestrian promenade 22 feet wide. On either side of this central zone are two 10-foot wide transit pathways. These vehicle lanes are slightly depressed and are paved with the same material as the remainder of the mall. The objective is to define the vehicle paths for safety in the least obtrusive way. At the edges, the existing sidewalk spaces are widened from 15 to 19 feet. The resulting cross-section yields several functional benefits. Existing utility lines generally stay clear of the center of the street (where trolley tracks once ran) so the tree roots will avoid utilities. A crumbling collection of vaults that exists under about half the present sidewalks can be rebuilt or phased out incrementally since the two major mall elements-transit paths and trees --can be installed independently. The center of the mall can be thought of as a dilation zone of new public open space as opposed to sidewalk areas which are more quasi-private spaces --adjuncts to the shop themselves. The plan provides a full complement of new lighting, benches, fountains, shelters and other amenities. But here we have stopped, for the plan by choice is a simple one. It is a framework and setting for both the present and future. Filling it initially with an array of podia, playgrounds or other fixed objects would preempt opportunities for creating new things later on. Ample space is provided for sidewalk cafes, kiosks, vending carts and displays which can evolve into permanent elements or change as different needs emerge.

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. ; End Blocks Looking at the 11-blocks between Broadway and Larimer Street, one senses three distinctive zones. The middle is a dense strictured. canyon of urban buildings. The western end opens to the grandeur. of the Rockies punctuated by the D & F Tower. The opposing end offers a tantalizing glimpse of the Capitol dome and rotunda. The design is organized to reinforce the separate identities of these three zones. At Curtis Street, the transit paths come together on the mall's north side and are bordered by a single row of trees for the three blocks to the Skyline transfer facility. At Tremont Place, the paths rejoin on the south side and, similarly, are bordered by a single tree line for the two remaining blocks to the Civic Center transfer facility, The result is a feeling of openness at the ends of the street and an enhancement of their views. The end block plans do not mean a sacrifice of greenery, however. It happens on those blocks where many existing buildings are set back from the right-of-way or where there is vacant land. These "side spaces" can be landscaped to augment the mall greenery without diminishing street vistas.

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THE TRANSITWAY/MAlL PlAN ',: .. : lil.. : 8 ..

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PlAN ElEMENTS The essential elements of the mall are paving, planting and lighting. Done well, these alone will transform 16th Street into a handsome, memorable pedestrian environment. The following pages illustrate these elements in detail together with the ancillary' street-furniture components of the plan. overleaf: A composite of mall elements on a typical block. The pattern and color of paving defines and organizes the functions along the street. w=-c:,. g;

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Paving As in a room with Persian carpets or intricate parquetry, the quality of the floor can set the tone for the whole interior space. The same holds true for outdoor spaces. More than any single element, the paving material will establish the character of the mall. For this reason we have selected a varied and intricate pattern. Its most basic geometry is a 45-degree diagonai grid responding to 16th Street's 45-degree juncture with Broadway and the surrounding city street system. Its design will also encourage diagonal movement within the mall. But the visually dominant pattern emerges more through a progression of color, shape and size. We have used three tones: two of gray and a muted red. It begins along the street wall as a field of gray paving block which gradually builds in scale as it reaches the center of the mall. The pattern at the edges is deliberately neutral to avoid competition with the varied dimensions of storefronts and doorways. In the center zone, the pattern becomes more colorful and dominant. The adjacent transit paths, depressed three inches, are clearly delineated by tone and pattern. Planting The selection of the honey locu,st as the appropriate tree for 16th Street emerged through an analysis of some 72 species evaluated in terms of several dozen criteria. These included height and diameter, trunk:, branch, leaf and root form, shade characteristics, sun, water and maintenance needs, disease and insect susceptibility, wind and pollution tolerance, availability and cost. The list was narrowed to six contenders and several specimens of each already in place in the Denver area were examined and evaluated more closely. The honey locust is already familiar on the streets of downtown Denver. Its characteristics make it a desirable urban street or mall-tree. The branch and leaf structure is light and lacy. The tree provides shade but will also create dappled, flickering light on paving surfaces. Its lifespan is long and it is resistant to drought, wind exposure and air pollution. It thrives in partial shade. It can safely be transplanted in 6-to-7-inch caliper sizes (the trunk diameter measured 12 inches above the ground) and 20-foot heights. In 5 years it will mature to 10-inch caliper and 35-foot heights. It requires a moderate amount of water and minimum maintenance.

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''.: ,;. Lighting The lighting concept for the transitway/mall employes a variety of techniques and fixtures for illuminating sidewalks, transit paths, center zone and intersections. is a double row of specially designed 11-foot high pole luminaires placed along the center zone. These will provide glare control and correct lighting angles to flatteringly illuminate trees, pedestrians and pavement. The fixture, a clear plastic globe with aluminum reflector and bronze standard, creates several distinctive lighting effects. The reflectors up-light undersides of trees and illuminate the center mall beneath. As twilight approaches soft "glitter lights" will turn on providing a gradual shift from natural to artificial light, and enhancing mountain views at dusk. Later at night, security lamps placed on the standards just below the main luminaire globe will be switched on to light store fronts and pedestrian areas. Store display lighting will be used to illuminate sidewalk areas, and street 9rossings will be lit by waist-high bollards to softly illuminate pavement areas where trees are absent. Small "runway" lights embedded in the pavement will be placed in the center of the' transit vehicle lanes as a guide for the vehicles, a reminder to crossing pedestrians, and to bring the pavement to life at night. We recommend that lighting for all cross-street approaches between 16th and 17th Streets be modified to allow a graceful transition to the new soft ambiance of 16th Street. The existing mercury vapor luminaires should be replaced with lower wattage metal halide sources placed on existing poles. This will produce better color rendition, less glare and better visibility at reduced energy consumption levels.

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I I Street Furniture In addition to paving, planting and lighting, the plan provides a full complement of street furniture and reorganizes the present array of sidewalk elements into a more coherent pattern with more uniform design. BENCHES: Six 9-foot benches are located on each block in the center zone of the mall. SHELTERS: A transit vehicle shelter is located at each transit stop at the near side of each intersection (two per block). PLANTERS: A series of low, round flower planters are placed along the mall on each block. FOUNTAINS: Major fountains are located at Curtis street and at Tremont Place, marking the points where the split transit paths rejoin at the end blocks. As future development takes place along the edges of the mall, there will be opportunities for introducing additional water, environmental sculptures and other mall-related amenities. INTERSECTION BANNERS: A special bronze standard and mast arm has been designed to hold required traffic control and pedestrian signals. The standards support a cable for decorative flags and banners announcing downtown events and marking the approaches to the mall from side streets. BIKE RACKS: Racks will be installed close-in on the intersecting side streets and will be linked to the city bike-way system. MISCELLANEOUS: Mailboxes and newspaper dispensers are grouped along the outer edges of sidewalk areas. Metal trash recepticles are placed throughout the center zone and sidewalk edges. !f: r,-C;!.:_; il: .. ..__ [J.

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Transitway Vehicle RTD has engaged General Motors to design a battery-powered vehicle system for the transitway. Its purposes are to collect and distribute express bus passengers between the two transfer facilities and various st-ops along the mall, to serve as a general mall circulation system, to serve passengers from the local bus routes that intersect the mali at California and Stout Streets. The vehicle fleet will carry up to 10,000 passengers per hour. During peak hours, two vehicles will operate in tandem, and in other hours as single units. Each vehicle can carry 44 passengers and 2 wheelchair passengers. Throughout the day they will maintain 70-second intervals in both directions and will travel at a top speed of 15 miles per hour with an average speed of 7 miles per hour. Stopping at each block, a roundtrip will take 15 minutes on this free-fare shuttle system. The vehicles are 22 feet long, 8 feet wide and 7. 8 feet high. The floor height is low (12-inch) and doors are wide for short boarding time and easy entry by the elderly and handicapped. Mall stops and terminals will have low platforms flush with the vehicle floor. Large glass areas will provide passengers with views of the mall and will minimize the impact of the vehicle on the mall visually, The driver-operated vehicles will run quietly on rubber tires and will be pollution-free. Routine maintenance and battery change and recharging will take place within the the Skyline transfer facility.

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FUNCTIONAL REQUIREMENTS Traffic Circulation The traffic plan for downtown Denver has been the subject of extensive technical effort. Barton-Ascbman and Associates, transportation and traffic engineering consultants, has worked with an inter-agency task force comprised of RTD, the Colorado Department of Highways,. and the City and County of Denver to devise a workable traffic plan which accommodates private automobile movement, maintains overall circulation within the central business district and meets the operational requirements of the transitway. The traffic concept provides for the use of 16th Street by transit shuttle vehicles, pedestrians, and emergency vehicles only, and permits all the named streets to intersect and cross as at present. Fifteenth Street, which is now one-way to the southeast will become one-way to the northwest. Fourteenth Street will also be reversed from its present direction, and 13th Street will become two-way. Cleveland Place will be deemphasized and Court Place will be reversed to provide flow to the northeast. Tremont Place will be reversed to provide flow to the southwest, and Glenarm Place will become a t;w6-way street under the traffic plan. Traffic flow around the Civic Center will occur along East Colfax Avenue, leading to 15th Street for those travelers headed northwest. For those moving from the central business district to the east and south, 14th Street will flow into Bannock, which will become one-way southbound between Colfax and 14th Avenue, and lead into 14th Avenue eastbound. Cherokee Street will }Jecome one-way northbound, Through this traffic circulation system, adequate capacity is maintained for private vehicle movements. Access is also assured to the parking garages, hotels, and other buildings which require direct service. Iii= li= [ [ [ [ [ [

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Downtown Circulation Plan Key ......,. Exclusive Bus Lane :'!,,;,<::: 16th Street Mall Transitway Terminal Vacated Street -. Direction of Flow

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Service and Emergency Access The servicing of stores and office buildings will continue to take place in alleys and delivery trucks will be permitted to cross the mall. In those few cases where alleys are discontinuous, service vehicles will use the transit path to the nearest named street. Delivery hours will be enforced to minimize disruption of transit vehicle schedules along the mall, especially during peak hours. While construction of the mall is not contingent on alley closures or revamping of store servicing arrangements, there will be future opportunities for closing alleys or turning them into pedestrian ways as new development or renovations take place. It is our hope that at least one prototype alley closing can be included at the time of mall construction. For the short term, alleys should be gently lit by sources placed at their 16th Street entrances to alleviate their "black hole" appearance. We propose a band suspended 14 feet high between buildings to support and to shield this light source. This will also tend to strengthen the visual continuity of the building wall along the street. Ambulances, fire trucks and similar vehicles will utilize the transit paths for emergency access to buildings on 16th Street. The center zone of the mall has been. kept clear of permanent obstructions and can also be used in emergencies. This area would become a bypass lane in the event of a transit vehicle breakdown. FT _,.._,;,)' f1 [!" --u [J [J !::} !:= I !f .I I ff I I l I fi g ff ... .l Jm-=. L I 'II::-l i (t .1 "'-" I" l -.1 ;L_..J ...... r I-L, t_:. I 1 ; fT. j ,._. 1 : I 1 I

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Utilities and Vaults Underground 16th Street, predictab];y, is a twisted maze of sanitary and storm sewers, water, gas and steam lines, electric ducts, telephone and street light conduits and other utility paraphernalia in use or long ;abandoned. At the street surface are the usual appendages of this system: .traffic signal poles and control boxes, light standards, catch basins, man. hoies, fire hydrants and assorted valves. Ideally, mall construction would provide an opportunity to sort out, reorganize and rebuild utilities into a more efficient and easily accessible consolidated system. Practically, however, this would be a time consuming, expensive and very complex process. Our design mandate was to prepare a mall plan that could be implemented in a short period without requiring, as a prerequisite, other major 16th Street improvements or expenditures by the public or private sector. Accordingly, the transitway /mall is designed to be constructed without extensive utility adjustments. Existing utility lines generally run in two parallell6-foot bands adjacent to existing curbs. The center of the street, where the trees are to be, is clear of lines that would otherwise have to be relocated to make space for root balls. Present lines will be accessible from the transit paths and the outer edges of the widened sidewalks. Manholes will be concealed beneath specially designed removable lids made of paving block. Fire hydrants will be shifted slightly, where necessary, to fit neatly with the paving module. Catch basins will be relocated and augmented as part of the overall mall drainage system. Utility lines running cross-mall under alleys and side streets will remain accessible since there will be no permanent obstructions in their Perhaps the thorniest problem of the mall is vaults. Under approximately half the existing sidewalks between Broadway and Larimer is a collection of underground rooms --old, in use or abandoned, structurally sound or fragile. In many cases, their roofs are simply the concrete sidewalk slab above. Each vault must be investigated in detail and dealt with separately. Some active ones must be completely reconstructed and some abandoned ones must be sealed off. If necessary, this process can take place incrementally. The building of the mall does not demand the whole job be done at once since no trees are to be planted there and no transit or emergency vehicles will run there. The final paving would simply await installation until a particular vault problem is resolved. Certainly, though, it would be best to do it all during the initial mall construction period. We have developed a system for dealing with vaults during construction of the transitway/mall. Below-grade concrete walls spaced 21 feet apart, perpendicular to the street, would be built in the vaults f;rom store front to curb. A temporary store security wall would be constructed across front face of each store basement. The concrete walls would then receive a structural concrete slab upon which the paving would be installed. At the completion of mall construction, the basement security wall could be removed to allow re-access to the vault area or, if the vault is to be abandoned, the wall would be made permanent -

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TRANSfER fACILITIES The success of the transitway/mall depends heavily on an innovative approach to the transfer facilities located at either end. Two factors are of particular importance: efficiency and environment. First, the transfer points will be operationally efficient. Buses will enter, circulate, unload, load, and leave on precise schedules. Pas sengers will transfer between bus and mall vehicle in a direct, clear line, and mall vehicles will pick up and deliver passengers at an even rate to keep their scheduled rounds along 16th Street. Environmentally, these transfer facilities will be much more attractive than stock bus depots. In fact, they have been designed as new centers of downtown activity and life that go well beyond their immediate transportation mission. They will provide high, open, sky lit public spaces filled with shops, cascading water, flowers and greenery. They will employ the latest technology to eliminate noise and fumes. They will respond to their urban contexts by creating new pedestrian links to tie the downtown core more tightly together. And, they will inchtde substantial office, retail and possibly residential uses to augment the terminals as vibrant downtown focal points. Civic Center The Civic Center transfer facility marks the southeastern end of the transitway and occupies. the block bounded by Broadway, Lincoln, Colfax and 16th Avenue. It will be used by all express buses from the southern and eastern urban area. The terminal has three main levels: a bus concourse, a transit vehicle interchange at Broadway, and an upper plaza level opening to Lincoln Street. Two mixed-use structures rise above the terminal complex. r:;:: --I,__.,. t!: '[ ..

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Concourse Level Key lll Plaza & Concourse Shops II Mechanical Transit Vehicle --IIIII Bus Transitway Level

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i I J I CONCOURSE LEVEL: Buses enter the terminal from 16th Avenue, ramp down, and circulate about a central pedestrian concourse ringed With 14 bays. Loaded buses return to ground level and exit either to 16th Avenue eastbound or to Broadway southbound. The pedestrian areas are screened from buses by sound-absorbing baffles and glass much like a jet port arrangement where planes are kept hidden from waiting Doors will give direct access from the concourse to the interior of each bus. The concourse, with its high ceiling is linked to the upper level through a wide central opening containing escalators and stairs. Auxilliary stairs and elevators for the handicapped are provided at either end. TRANSITWAY LEVEL: Transit vehicles enter the terminal from 16th Street beneath an open double-height, sky-lit roof. Passengers unload close to the concourse portal, where they escalate down to the bus level. A suspended electronic display board will inform passengers where their bus is waiting. Small shops and boutiques line one side of the space and a linear waterfall provides additional animation apd soft sound. An estimated one-quarter of the bus patrons will walk from the terminal to thein destinations in the downtown. PLAZA LEVEL: Lincoln Street is approximately eight feet above Broadway and, accordingly, the design provides an upper plaza which leads to the State Capitol and surrounding government offices. The terminal comple:le will thus provide a new visual and functional link between 16th Street and the Capitol area. AIR-RIGHTS The block is a strategic downtown site -too important to be used only as a terminal. The proposed mixed-use development will fulfill the site' s potential, create a strong new physical .focus in the downtown, and add to the life of the complex. Two triangular towers rise above the terminal skylight framing an open vista on ms with 16th Street and opening the mall to views of the Capitol dome beyond. The towers vary from 10 to 20 floors responding to the sight-line and building height restrictions that protect views from the State Capitol. All in all, 740,000 square feet of usable office space are provided.

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Section Key II Plaza & Concourse B Shops B Offices II Mechanical Plaza level

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Concourse Level Skyline The Skyline transfer facility will be located at the northwestern end of the transitway. It is here that downtown-bound buses from the north .. and west will be intercepted and passengers will transfer to the mall vehicles, Several potential sites have been investigated and a prototype ,. for the terminal has been designed. The functional organization will be similar to that of the Civic Center transfer facility. Buses will enter and ramp down to a central pedestrian concourse. Bus bays will be provided, and passengers will move directly up to the transit way level through a central portal. Mall vehicles will loop into the terminal to pick up or discharge riders within a high, naturally lit space lined with retail shops and commuter conveniences. The Skyline transfer facility will include office or residential uses above as well, and will create new pedestrian linkages to Larimer Square and Lower Downtown. Key lfi Plaza & Concourse Shops lj Maintenance Vehicle Bus Transitway Level ........ K. ('" E. c IT [[ IT u:. -