THE DRIVERLESS STREET Re -imagining the Urban Street in the Age of Autonomous Vehicles
Nicolette Ward
Advisor: Timothy Stenson
Spring 2018 Thesis
CONTENTS 02
Contention 04
Evolution of Streets 10
Autonmous Vehicles 16 Site 18
Street Analysis 26
Precedent Analysis 32
Strategy 34
Sources
Contention
Since the advent of automobiles, city street design has privileged vehicular needs – drive lanes, park-
ing, etc. Indeed, even predating cars, wider, straighter streets were developed as “progressive” urban improvements. With twentieth century increases in vehicular traffic volume city streets grew wider, and wider. Engineering paraments of volume, speed, turning radii, taxis, busses, through traffic, etc. now govern city street design. Of course, and almost without fail, traffic volume overwhelms designed capacity. Urban traffic congestion comprised of large volumes of stopped-to-slow-moving cars and trucks results in high local pollution levels. Mixed in with the traffic, yet squeezed to the edges, pedestrians are subject to inhospitable, and unhealthy urban street space.
90% of car related deaths are caused by human error. Driverless cars would eliminate human error and
reduce fatalities significantly. Up to 30% of urban traffic is generated by drivers looking for parking. Driverless cars will essentially eliminate the need for parking as they are constantly on the move for a new passenger. There are over 1 billion cars in the world, but they sit idle 96% of the time. The space that will be freed up by driverless cars is staggering and its our job as architects to design it.
The introduction of autonomous vehicles will bring opportunities to shift the dominant user of streets
from the vehicle to the pedestrian. This shift in significance among users will lead to major changes in the dynamic of a typical urban street; a shift in scale from vehicles to pedestrians as well as shifts in speed and program could have profound architectural effects in regards to street design elements such as scale, materiality, building interface, and dimension. Recognizing street-space structure as “stranded” – comprised of multiple parallel bands of use – this proposal will reconfigure the public space of city streets: braiding, bending, folding, seaming, intertwining the spatial form of these strands to better accommodate pedestrians as well as autonomous vehicles.
Architecture currently plays a minor role in the design of streets – transportation engineers reign, but
as the amount of cars needed decreases and the pedestrian gains higher significance, an architecturally driven strategy to street design can be implemented. AV advanced mapping and maneuvering technology will allow them to drive and park much closer together, allowing for a reduction in lane width and parking spaces. Various studies looking at the use of ridesharing and the expected technology of driverless cars predict that it will be significantly cheaper for urban residents to use ridesharing in a driverless vehicle as opposed to having a personal car or hailing a cab. Ridesharing and the efficiency of driverless cars will lead to a dramatic decreases in the both the amount of driving lanes and the width of driving lanes. The need for parking spaces will effectively disappear. With these changes in traditional street layout, a question is raised regarding the architectural implications and opportunities of this abandoned space; if an entire lane of traffic is no longer needed then how should that space be repurposed?
CONTENTION
02
This thesis aims to utilize the benefits that driverless cars will bring in order to design an inhabitable and
dimensional urban street through the introduction of an additional layer of public space. This investigation is used as a test case. The new street is aimed at providing a better environment for pedestrians and cyclers while also accommodating driverless cars.
In analyzing the fabric and elements of an existing street in Boston, a theme quickly becomes apparent;
the street consists of numerous layers of divisions and lines, both two dimensional and three dimensional. These lines start to form many partitions within the context of the street and create separations in program, scale, speed, material, etc. Some lines can be crossed, some can be stepped over, some can be walked through, some can be used.
The architectural strategy of the project is informed by this mapping and analysis, which revealed a
stranded condition of space and elements throughout the street. The concept of strands as space and weaving as a way of making space is utilized in order to accommodate several modes of movement and activity within the street. The strategy is two fold and it consists of a systematic landscape as one part and exceptional interventions as the second. The back and forth dialogue between the systematic and the exceptional is continuously exemplified in the armature which runs throughout the street and terminates into the park.
et tre
dth
Wi
S
Street Width
Pre-1880
Pedestrian Dominated Winding, Narrow Roads
1880-19201
Pedestrian Dominated Roads Widened Street Grids Used
920-present
Vehicle Dominated New Highway Infrastructure Pedestrians Pushed Out of the Street
Future Possibility Simultaneous Accomodation of Vehicle & Pedestrians Streets get narrower
The Evolution of Streets Haussman and the Re-building of Paris
Haussman’s rebuilding of Paris sought to improve the health of of the streets which were at the time very narrow and lacked light and air. They also had open sewage gutters that negatively affected the health of the streets. His new avenues were wider and cut through some of the existing dense fabric of paris. The new streets were laid out Monumental SpaceBy widening the streets he also sought to let more light and air in and to be linear and less confusing to navigate.
allow for room for activites and celebration. -Allow pedestrians to appreciate architecture -Creat beautiful squares
Evening on the Boulevard in Paris, Luigi Loir
Streets were widened to allow for light, air, and activity.
Paris Street; Rainy Day, Gustave Caillebotte There was a strong desire for beautiful and large open spaces where people could appreciate architecture.
EVOLUTION OF STREETS
ISSUES
SOLUTIONS
Narrow Streets
Widened Streets
Confusing Layout
New & Symmetrical Roads
No Beautiful Avenues & Squares
Constructed Monuments & Parks
Open Sewage Gutters Lack of Light & Air
04
Expanded Sewer System Wider Streets & Gas Lights
The plan for new avenues cut through a dense existing fabric and cleared out old buildings to make room for the new.
Map of Paris c. 1850
Map of Baron Haussmann’s new boulevards and avenues.
A picture taken during the construction of the Avenue de L’opera
The modern Avenue de L’opera
The Evolution of Streets Camillo Sitte
Camillo Sitte’s criticism of late nineteenth century urbanism is rooted in an argument to plan cities using
artistic principles and using established medieval planning methods that form a sense of place. Sitte argues that an urban space needs to give a feeling of enclosure and that this can be achieved through curved roads and placement of monuments. Enclosure is not achieved in grid locked city plans due to the endless vistas of linear streets. He also argues against the method of block planning as it inevitably places streets and open areas in the leftover space.
Endless Vistas No Buffer Between Foreground & Background
Focused Vista Partial Enclosure
Controlled Vista Buffer Between Foreground & Background Enlosed
Evolution of Streets
Planning Blocks - Open Space & Streets are Leftover
Planning Open Space & Streets
10 Vistas
Hierarchy of Streets
06
5 Vistas
1 Vista
Grid-lock, No Hierarchy
The Evolution of Streets Camillo Sitte
“
“In former times the open spaces—streets and plazas—were designed to have an enclosed character for a definite effect. Today we normally begin by parcelling out building sites, and whatever is left over is turned into streets and plazas.” (Sitte, 1945)
Camillo Sitte and Leon Krier believed that streets should have diverse and perhaps picturesque vistas and thus the elevations should vary as one moves along so that they constantly
Elevation from Poundsbury, UK
appreciate a new view.
These idelas went against the ideals of modernist planners like Haussmann who utilized coherence and repetition along very wide and linear streets.
Elevation from Boulevard Haussmann, Paris
Evolution of Streets
08
Venice & Florence
1.
Venice Street Sections
2.
Florence Street Sections
1.
The streets in Venice are unlike anywhere else due to their lack of cars. The canals in venice serve
as “streets�. Through analyzing the unique sections of various instances in Venice, one can begin to understand the street at different scales. Bridges are prominently used and show a smoother crossing between pedestrians and vehicles (boats). 2.
When looking at street sections in Florence, it becomes clear that the streets are at a human scale.
Several streets are just big enough for a single pedestrian while others serve as a platform for adjacent buisnesses to spill activity onto the street.
1.
2.
Autonomous Vehicles How Driverless Cars Will Change Cities
Ro m an Z a k h a re n k o dis cus s es the impacts that dri verless cars w i ll have on exi sti ng urban fabri c in h is a r t ic l e t i tl e d “Se l f - d r i v ing car s will change cities” and he concludes several key poi nts based on re se a rc h a n d t ren ds; c i ti e s w i l l expand, res idential dens i ty w i ll shi ft to the peri phery, economi c densi ty w i ll in c re a se in t h e co re of th e c i ty, and a “par king belt” will emerge.
Cities will expand. W i th the i ntroducti on of autonomous vehi cles, peopl e wil l be able to commute easi er and use thei r travel ti me in a
producti ve manner. Therefore, i t w i ll be more appea l in g t o resi de further from the center of the ci ty. (Zakharenko, 2016)
Residential density will shift. As people move further away from the center of the city, the residential density of the core will decrease. (Zakharenko, 2016)
AU TO NO M O U S V E HI C L ES
10
Economic density will increase. A s res i d e n ti a l d e n s ity mov es towards the e dge of the ci ty and as parki ng lots and garage s a re a b a n d oned, economic dens ity w i ll take over thi s space and expand w i thi n t h e co re of th e c i ty. (Zakharenko, 2016)
“Parking Belt” will appear. Zakharenko claims that the effects of autonomous vehicles may lead to the emergence of a “parking belt” in addition to the increased central economic activity and shift in residential density. (Zakharenko, 2016)
Dense Economic Core Parking Belt Residential Periphery
Autonomous Vehicles How Driverless Cars Will Change Cities
Numero us s c h o lar s an d st u d i es d i sc us s the a d v a n ta ge ou s e ffe cs that d r iv e r l e s s cars wi ll have o n o u r c i ty st reet s. T h ei r i n t ro d uction is expe cte d to a l l ow for re d u ction in l ane wi dths, in cre a s e s i n ro a d way c ap ac i t y , eli m i n ation of pa r kin g s pa ce , a n d re m ov a l of s ign age geared toward s ve h i c l e s.
25%
Red u c t i o n i n lan e w i dth ( ex. from 1 2ft to 9ft)
50%
In c rease i n ro ad way c a pa city Par k i n g lo t s an d g arage s w il l n o l on ge r b e n e e d e d R ai li n g an d si g n age f or v e hicl e s ca n b e e l im in ate d (Bowman, 2016)
“
“I n ter m s of infrast r u c t u re , e v e r y t h i n g f rom st ree ts to c ur b s to s i d ewa l k s w i l l n e e d t o change wh en the a utonom o u s c a r m a k e s i t s o f f icial debut.” (B owman, 2 01 6)
NOW
FUTURE
Static Congested Limited Green Space Vehicle dominated
Dyn a m ic Efficie nt G re e n Wa l ka b le
AU TO NO M O U S V E HI C L ES
The definition between the street and the curb won’t be as necessary.
There will no longer be a need for street parking. Instead there will be a need for pick up and drop off zones.
There will be more space for foilage and pedestrian paths won’t have to be as strictly defined.
12
Autonomous Vehicles From Owning to Sharing
Current Private Vehicle
Future Shared AV
20¢
40¢
60¢
80¢
21¢
Operating Cost
61¢
Fixed Cost
17¢
Operating Cost
26¢
Fixed Cost
per mile
per mile
per mile
per mile
100¢
*Based on a chart from KPMG’s “Marketplace of Change: Automobile insurance in the era of autonomous vehicles” (2015)
“
“During the past five years, the Zipcar Annual Millennial Survey has consistently shown that millennials in the United States (regardless of where they live) report specific tendencies: t h e y f i n d i t d i ff i c u l t t o o w n a c a r ; t h e y w o u l d g e t r i d o f t h e i r c a r , TV or computer before they’d give up their mobile phone; they have a strong desire to protect the environment; and they are o p e n t o a l t e r n a t i v e f o r m s o f t r a n s p o r t a t i o n . ” (Zipcar, 2015)
AU TO NO M O U S V E HI C L ES
Physical Implications of New Technology
Reduction of Lanes 4-lane streets can be converted to 2-lane streets without losing capacity (Snyder, 2016) 12ft
9ft
Smaller Inter-vehicle Spacing Lane size can be decreased from 12ft to 9ft (Bowman, 2016)
Platooning Using connectivity technology, multiple vehicles can travel together at maintained high speeds. A dedicated lane for platooning vehicles would be most efficient.
12ft
9ft
14
Site Boston, Massachusetts boston commons
s o u t h s t at i o n
Project Site (Summer Street)
South Boston Waterfront
Marine Park (AV Testing)
W i th th e i n troduction of new trans po rtati on technologi es, there w i ll li kely be maj or ch a n ge s in t h e
way ci ti e s a n d th e ir infras tr ucture operate. Although there have been many speculati ons on the p o ssib l e im p act s o f a u ton om o us v ehicles , people hav e n ot yet begun to plan for these changes at an urban sc a l e . B o st o n i s l ead i n g th e wa y in this s ector , s ince it re leased a w hi te paper i n January 2017 about the co n n e c t io n b e t ween a u to n om o u s v ehicles and ur ban planni ng. Boston also released the “Go Boston 2030 Vi si o n a n d A c t io n Pl an � w h i c h f o c u ses on the future of the city w i th regards to transportati on changes and develo p m e n t s.
S ITE : BO STO N
16
Autonomous Vehicle Initiatives in Boston - The Future of Urban and Autonomous Vehicles Boston was selected as a focus-city for policy and pilot development of autonomous vehicles. - Smart City Collaborative
Boston is collaborating as an autonomous vehicle working group.
- Low Speed Automated Shuttle Research
The City of Boston is part of the Low-speed Automated Shuttle Working Group.
- Go Boston 2030 Vison and Action Plan
This transportation planning initiative identifies autonomous vehicles as a way of improving
the city and accomplishing their 3 goals: access, safety, and reliability.
- Pilot Testing of Autonomous Vehicles
Testing of autonomous vehicles is currently underway in Boston in the Raymond Flynn Marine
Park and South Boston Waterfront.
City of Boston (Phase D) South Boston Waterfront (Phase C)
Marine Industrial Park (Phase A&B)
Street Analysis Summer Street, Boston
20-25 ft 18-20 ft 20-25 ft 30-35 ft 35-40 ft 30-35 ft 35-40 ft 45-50 ft 45-50 ft 60-65 ft
Street Scale 70 ft
Vehicles 10% Pedestrians 90%
Vehicles 80% Pedestrians 20%
Vehicles 50% Pedestrians 50%
Vehicles v. Pedestrians
Summer Street
S T R E E T A N A LY S I S
Contours
Massing
18
Street Analysis Street as a Landscape Divided by Strands of Elements
T h e s t r e e t l a n d s c a p e i s l i t t e r e d w i t h m a n y d i ff e r e n t e l e m e n t s , e a c h s e r v i n g a c e r t a i n p u r p o s e
for pedestrians or vehicles. Upon analysis, it is clear that these elements have a typical placement along the street and varying degrees of repetition. As a result, lines or strands of elements run parallel
throughout the landscape and divide the space. These elements are catalogued and their “strands” are identified and mapped within the streetscape.
N
Lincoln St
N°5 S L
Purchase St
N°6 B R
Atlantic Ave
N°7 P
N°8 T & R
20
S T R E E T A N A LY S I S
N
Atlantic Ave
Dorchester Ave
N°1 S B
N°2 S L
N°3 C
N°4 T
Street Analysis Sectional Analysis
D
C
B
A
D
C
B
A
South Station
22
S T R E E T A N A LY S I S
I
H
G
F
E
I
H
G
F
E
Boston Commons
Street Analysis Sectional Analysis
The section of the existing street reveals a typical condition of our streets today. The majority of
the street is dedicated to vehicles and the pedestrians are pushed to the edge. Another condition that becomes apparent is the way that the street becomes divided by strands of objects. Curbs and lines and
Aesthetic Structure
Aesthetic Structure
Curb Light Posts Bollards
Lane Divider
Building
Pedestrian
Parking
North
Driving
Pedestrian
Driving
Driving
Parking
Pedestrian
Pedestrian (Covered)
Driving
Summer St
South
Building
Lane Divider
Curb
Curb
Lane Divider
Awning
Light Posts Curb
Lane Divider
lamps are utilized as a way of dividing up the street space and sepereating uses.
Summer St
Vegetation
Pedestrian
Driving
Driving
Driving
Pedestrian
Driving
South
Driving
Pedestrian
Building
Trees
Light Posts
Curb
Lane Division
Lane Division
Curb
Curb
Lane Division
Light Posts Curb
Bollard
S T R E E T A N A LY S I S
24
North
Section CC Curb Light Posts
Lane Division
Lane Division
Lane Division
Curb
Light Posts
Planter
Planter
Planter
Section BB
45 ft
Light Posts
Curb
Lane Division
Lane Division
Curb
Curb
Lane Division
Curb
Light Posts
Bollard
Street Analysis
Sectional Analysis
60 ft
Section EE Awning/signs
Curb
Lane Division
Lane Division
Lane Division
Curb
Light Posts
Curb
Lane Division
Lane Division
Lane Division
Light Posts Curb
S T R E E T A N A LY S I S
40ft
75ft
Section DD
60ft
40ft
26
Section GG Trees
Canopy
Light Post
Curb
Lane Division
Canopy
Planters
Curb Trees
Lane Division
Curb
Trees
Street Analysis
Sectional Analysis
60ft
30ft
Section FF
60ft
30ft
Signs
Section II Signs
Gutter Light Post
Light Post Gutter
Section HH
20ft
Canopy
Light Post
Light Post
Gutter
Canopy
S T R E E T A N A LY S I S
60ft
28
Strategy Contextual Strategy
It may be the case that we are not reliant on a total transformation when driverless cars become
widespread. Instead, my expectation is that even before every city street is physically altered, traffic patterns will change because the computer regulated system in vehicles will make it possible for traffic to flow in more efficient ways. Even before this total physical transformation, the technology will likely offer opportunities to selectively redesign certain streets. In my own investigation and site which is in Boston, these selective streets radiate out of the Boston Commons like spokes. As of right now, redesigning a street would have major effects on drivers and their sense of location and direction. However, the mapping technology and sensors in driverless cars allow them to adapt to physical changes easily, so the physical tranformation of strteets would be possible without the negative effects that human drivers would experience.
ST R AT E GY
30
Strategy Exceptional v. Systematic
The design strategy of the project utilizes a dialogue between two systems: the exception-
al interventions and the systematic landscape. The systematic landscape consists of ramps and paths and it contains regular programs such as bathrooms, seating, and storage. The poche underneath the sloped paths contains temporal programs such as temporary pop up shops and exhibits. The exceptional interventions use actions such as wrapping, laminating, and infiltrating to tie a new layer of space into the existing fabric and to alter the exisitng street wall. The program of these interventions is point-specific and dependent on the existing street program.
32
ST R AT E GY
Exceptional Interventions
+ Systematic Landscape
$
Strategy Design Tactics
The design strategy of the project recognizes the street as consisting of strands. This
strategy can be brought down to a smaller scale when designing elements such as seating, lighting, and areas of vegetation.
( )
( )
( )
( )
( )
( )
( )
( )
( ) ( )
ST R AT E GY
( )
( )
( )
( )
( )
34
Systems
(1.) (2.) Structure Strategy
Structural Hierarchy
1.
2.
The project contains two types of walkways: one larger walkway that meanders back and forth to each side of the street and then a series of smaller walkways that slope up from the ground plane to meet the larger walkway. The strutctural systems reflect the hierarchy of the walkways. The larger walkway (1) uses a system of arched steel supports while the smaller ones (2) use straight steel columns and beams.
Intervention Structure
The exceptional interventions that exist throughout the project also reinforce the directionality of the porject. They use a steel column and beam structure and are cladded with metal panels that run parallel to the street. They are conceptualized as single large strands that bend up and back over themselves in order to form an enclosure. Glass is used to maintain openness while one moves perpindicular to the street.
Structural Directionality
The primary lines of structural support run parallel to the strands to reinforce the directionality of the project. The secondary system of structural supports run perpindicular to the strands.
SYSTEMS
Water Collection System
Intersection
36
Design Perspective from above
DESIGN
38
Design Sections
Section AA
DESIGN
40
Design Sections
Section BB
DESIGN
42
Design Sections
The series of sections throughout the street can be compared to the existing conditions
in order to reveal the transformation of the street through the addition of space for pedestrians and bikers. A reduction in the amount of space used for vehicles is also demonstrated. In several cases, the sections reveal the way in that the exceptional interventions intrude upon the existing street wall. Through this transformation, the street begins to take on a new scale and dimension.
Section CC
DESIGN
Section DD
Section EE
44
Design Sections
Section FF
Section GG
DESIGN
Section HH
Section II
46
Design Floor Plans & Program
a
b
a
YOGA STUDIO
b
PA I N T S T U D I O
c
E X I S T I N G : R E TA I L , F O O D
e
e
BIKE STORE
B AT H R O O M S , B I K E S , S T O R A G E , F L E X
E X I S T I N G : R E TA I L , S T R E E T P E R F O R M E R S
a
b
B AT H R O O M S , B I K E S
E X I S T I N G : R E TA I L , F O O D
b
a
d
d
ART MUSEUM
B AT H R O O M S , B I K E S , S T O R A G E , F L E X
E X I S T I N G : PA R K
c
c
c
d
d
e
e
48
DESIGN
f
g
f
h
g
i
h
CAFE
i
MARKET
S, STORAGE, FLEX
B AT H R O O M S , B I K E S , S T O R A G E , F L E X
E X I S T I N G : F O O D T R U C K S , O F F I C E S , PA R K
g
f
h
g
D AY C A R E
B AT H R O O M S , B I K E S , S T O R A G E , F L E X
EXISTING: OFFICES, PLAZA
f
BOOKSTORE
E X I S T I N G : T R A I N S TAT I O N , O F F I C E S
i
h
i
EXISTING: OFFICES
Design First Floor Plan Detail i
h
i
MARKET
BOOKSTORE
D AY C A R E
B AT H R O O M S , B I K E S , S T O R A G E , F L E X
E X I S T I N G : F O O D T R U C K S , O F F I C E S , PA R K
E X I S T I N G : T R A I N S TAT I O N , O F F I C E S
i
h
i
EXISTING: OFFICES
50
DESIGN
Daycare
Bookstore
Paths connect buildings
Program underneath “strands”
AV Canopy
Design Perspective from Boston Commons
DESIGN
52
Design Perspective from below
DESIGN
54
Design Model
DESIGN
56
Design Model
DESIGN
58
Bibliography “Autonomous vehicles: Boston’s approach.” Boston.gov. October 26, 2017. https://www.boston.gov/departments/new-urban-mechanics/autonomous-vehicles-bostons-approach. Alphand, Jean Charles Adolphe. Les Promenades de Paris. Paris, 1867. Alvarado, Estevan. “Haussmann & the Revival of Paris.” Museum of the City. http://www.museumofthecity.org/ project/haussmann-and-revival-of-paris/. “Boston Test of Self-Driving Cars Reveals Five Key Lessons for Cities Worldwide.” BCG. October 17, 2017. Bowman, John Jay. “How Autonomous Vehicles Will Change the Future of Road Design and Construction” FMI. September 1, 2016. Campbell, Mark, Magnus Egerstedt, Jonathan P. How, and Richard M. Murray. “Autonomous driving in urban environments: approaches, lessons and challenges.” Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. October 13, 2010. Cortright, Joe. “What price for autonomous vehicles?” City Observatory. September 28, 2016. http://cityobservatory.org/price-of-autonomous-cars/. “Cost-based Analysis of Autonomous Mobility Services.” ETH. April 2017. Fuller, Brandon. “Cautious Optimism about Driverless Cars and Land use in American Metropolitan Areas.” Cityscape: A Journal of Policy Development and Research18, no. 3 (2016): 181-84. Gibbons, Andrea. “Camillo Sitte: The Art of Building Cities.” Andrea Gibbons. October 04, 2016. http://writingcities.com/2016/10/01/camillo-sitte-art-building-cities/. Guerra, E. “Planning for Cars That Drive Themselves: Metropolitan Planning Organizations, Regional Transportation Plans, and Autonomous Vehicles.” Journal of Planning Education and Research36, no. 2 (2015): 210-24. Hill, Dan. “The Street As Platform: How Digital Dynamics Shape the Physical City.” Architectural Design85, no. 4 (2015): 62-67. Lang, Nikolaus, Michael Rubmann, Jeffrey Chua, and Xanthi Doubara. “Making Autonomous Vehicles a Reality:
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Lessons from Boston and Beyond.” BCG. October 17, 2017. Littman, Todd. “Autonomous Vehicle Implementation Predictions” VTPI. September 8, 2017. Pinjari, Abdul. “Highway Capacity Impacts of Autonomous Vehicles: An Assessment.” Rybczynski, Witold. “Behind the Façade of Prince Charles’s Poundbury.” Architectmagazine. December 3, 2013. http://www.architectmagazine.com/design/behind-the-facade-of-prince-charless-poundbury_o. Snyder, Ryan. “Implications of Autonomous Vehicles: A Planner’s Perspective.” Inside The Industry, December 2016, 25-28. Zakharenko, Roman. “Self-Driving Cars Will Change Cities.” SSRN Electronic Journal, 2016. “Zipcar annual millennial survey suggests being a ‘millennial’ is related to where you live, not when you were born.” News release, April 16, 2015. Zipcar. http://www.zipcar.com/press/releases/2015millennials.