ITE Journal March 2018 - 49

circles. Focus on safety and performance metrics like speed,
design vehicle accommodation, and path alignments, not on
individual elements like lane widths, curb radii, entry angles, etc.
ƒ Seek experienced roundabout consultants/designers/reviewers
who embody lifelong learning and teaching. Challenge them to
help you cut cost without cutting performance. They will often get
to a higher-performing design with fewer iterations and respond
to comments in a way that allows everyone to learn comfortably.

Researchers and Educators:
ƒ Study the wide range of design strategies used to cut roundabout
costs, in order to clarify their effects on Vision Zero-related
performance measures.
ƒ Collect data on the disparity between average roundabout and traffic
signal costs (excluding outliers) stratified by agency. This will help
counter the perception created by multi-million dollar roundabouts.
ƒ Teach your students the basic principles of modern roundabouts.

Designers:
ƒ Improve continuously. Learn relentlessly and share what you
learn generously.
ƒ Make the effort to obtain data before the project is built, then
measure the performance of your design once it is built. What
can you learn that will make your next design better?
ƒ Listen carefully to other designers, make sure you understand
the less obvious constraints they were bound by when
measuring the performance of their designs. What can be
learned that will make your next design better?
ƒ Take the initiative to share what you are doing and learning
through webinars, workshops, community posts, and professional meetings. Your work may even become part of the next
iteration of design guidance. (Keeping this valuable information
to yourself slows progress toward cost parity with traffic signals
and ultimately shrinks the size of the roundabout market you
will be able to compete for over your lifespan.)

Conclusion
With the Vision Zero movement, public agencies are seeing that
roadway infrastructure change is urgently needed to save lives.
Roundabouts make a great part of any long-term strategy for
achieving Vision Zero.
Many roundabouts are currently being over-designed and
over-built. This leads to greater costs and fewer safety benefits (due
to higher speeds), which is slowing the shift from roundabouts
being an alternative to them being the norm. As engineers
continue to learn and refine the balance needed to create low-cost,
high-performing roundabouts, they will soon reach cost parity
with traffic signals, and eventually most traffic signals will end up
becoming roundabouts. itej

References
1. https://safety.fhwa.dot.gov/intersection/innovative/roundabouts
2. https://ec.europa.eu/transport/road_safety/sites/roadsafety/files/
pdf/20151210_1_sweden.pdf
3. http://teachamerica.com/RAB17/RAB172A_VonAhsen/presentation.html
4. www.dot.ca.gov/research/researchreports/reports/2007/roundabout_
geometric_design_guidance.pdf
5. www.cityofboise.org/city_clerk/103012/achd.pdf
6. www.dot.ca.gov/trafficops/ice.html

Fine Print

Phil Rust is Chair of the ITE Standing Committee
on Roundabouts. He collected data for the second
U.S. roundabout guide. Phil met his wife at a
roundabout conference. He picked up a traffic signal
hobby and is now horribly conflicted. Phil is
currently a traffic engineer with the City of San
Diego, CA, USA. He previously worked for the Ada County Highway
District in Boise, ID, USA and for the Washington State Department
of Transportation. He earned degrees from the University of Idaho
and Washington State University and is currently licensed in
California and Washington State. He ran the California
International Marathon in more than 4 hours. Phil is a
member of ITE.

There will always be resistance to change from a variety of sources,
so the shift to implementing more roundabouts won't come
overnight or without effort and losses.
Traffic signals and roundabouts have different footprints, so
even when average roundabouts are cheaper than average traffic
signals, individual outliers will continue to exist, and those
roundabouts will continue to compete well on value.
Regardless of cost, there will always be intersections where
a roundabout is not the best form of intersection control. These
intersections don't lend themselves to the rules of thumb that some
lists suggest, but they do exist. When in doubt, please consult an
experienced roundabout design engineer.

Lindsey Van Parys is a registered Civil Engineer in
multiple states and holds a certificate in Traffic
Collision Investigation. She has 10 years of experience in delivering transportation projects and is
currently a project manager who oversees project
operations. Her experience includes designing
roundabouts, streetscapes, trails, roadway/highway improvements,
and various other projects. She specializes in delivering roundabout
projects on the State Highway System. She has worked on dozens of
roundabout concepts, designs, and project delivery for projects
spanning from California to Florida.
w w w .i t e.or g

M arch 2018

49


https://safety.fhwa.dot.gov/intersection/innovative/roundabouts https://ec.europa.eu/transport/road_safety/sites/roadsafety/files/pdf/20151210_1_sweden.pdf https://ec.europa.eu/transport/road_safety/sites/roadsafety/files/pdf/20151210_1_sweden.pdf http://www.teachamerica.com/RAB17/RAB172A_VonAhsen/presentation.html http://www.dot.ca.gov/research/researchreports/reports/2007/roundabout_geometric_design_guidance.pdf http://www.dot.ca.gov/research/researchreports/reports/2007/roundabout_geometric_design_guidance.pdf http://www.cityofboise.org/city_clerk/103012/achd.pdf http://www.dot.ca.gov/trafficops/ice.html http://www.ite.org

Table of Contents for the Digital Edition of ITE Journal March 2018

ITE Journal March 2018 - 1
ITE Journal March 2018 - 2
ITE Journal March 2018 - 3
ITE Journal March 2018 - 4
ITE Journal March 2018 - 5
ITE Journal March 2018 - 6
ITE Journal March 2018 - 7
ITE Journal March 2018 - 8
ITE Journal March 2018 - 9
ITE Journal March 2018 - 10
ITE Journal March 2018 - 11
ITE Journal March 2018 - 12
ITE Journal March 2018 - 13
ITE Journal March 2018 - 14
ITE Journal March 2018 - 15
ITE Journal March 2018 - 16
ITE Journal March 2018 - 17
ITE Journal March 2018 - 18
ITE Journal March 2018 - 19
ITE Journal March 2018 - 20
ITE Journal March 2018 - 21
ITE Journal March 2018 - 22
ITE Journal March 2018 - 23
ITE Journal March 2018 - 24
ITE Journal March 2018 - 25
ITE Journal March 2018 - 26
ITE Journal March 2018 - 27
ITE Journal March 2018 - 28
ITE Journal March 2018 - 29
ITE Journal March 2018 - 30
ITE Journal March 2018 - 31
ITE Journal March 2018 - 32
ITE Journal March 2018 - 33
ITE Journal March 2018 - 34
ITE Journal March 2018 - 35
ITE Journal March 2018 - 36
ITE Journal March 2018 - 37
ITE Journal March 2018 - 38
ITE Journal March 2018 - 39
ITE Journal March 2018 - 40
ITE Journal March 2018 - 41
ITE Journal March 2018 - 42
ITE Journal March 2018 - 43
ITE Journal March 2018 - 44
ITE Journal March 2018 - 45
ITE Journal March 2018 - 46
ITE Journal March 2018 - 47
ITE Journal March 2018 - 48
ITE Journal March 2018 - 49
ITE Journal March 2018 - 50
ITE Journal March 2018 - 51
ITE Journal March 2018 - 52
http://www.nxtbook.com/ygsreprints/ITE/G110939_ITE_November2019
http://www.nxtbook.com/ygsreprints/ITE/G110110_ITE_October2019
http://www.nxtbook.com/ygsreprints/ITE/G110109_ITE_September2019
http://www.nxtbook.com/ygsreprints/ITE/G108559_ITE_August2019
http://www.nxtbook.com/ygsreprints/ITE/G108250_ITE_July2019
http://www.nxtbook.com/ygsreprints/ITE/G107225_ITE_June2019
http://www.nxtbook.com/ygsreprints/ITE/G104039_ITE_May2019
http://www.nxtbook.com/ygsreprints/ITE/G104038_ITE_April2019
http://www.nxtbook.com/ygsreprints/ITE/G104036_ITE_March2019
http://www.nxtbook.com/ygsreprints/ITE/G103582_ITE_February2019
http://www.nxtbook.com/ygsreprints/ITE/G102868_ITE_January2019
http://www.nxtbook.com/ygsreprints/ITE/G100155_ITE_December2018
http://www.nxtbook.com/ygsreprints/ITE/G100154_ITE_November2018
http://www.nxtbook.com/ygsreprints/ITE/G99495_ITE_October2018
http://www.nxtbook.com/ygsreprints/ITE/G98028_ITE_September2018
http://www.nxtbook.com/ygsreprints/ITE/G97366_ITE_August2018
http://www.nxtbook.com/ygsreprints/ITE/G96287_ITE_July2018
http://www.nxtbook.com/ygsreprints/ITE/G94315_ITE_June2018
http://www.nxtbook.com/ygsreprints/ITE/G93877_ITE_May2018
http://www.nxtbook.com/ygsreprints/ITE/G93065_ITE_Apr2018
http://www.nxtbook.com/ygsreprints/ITE/G91484_ITE_Mar2018
http://www.nxtbook.com/ygsreprints/ITE/G89434_ITE_Feb2018
http://www.nxtbook.com/ygsreprints/ITE/G86608_ITE_Jan2018
http://www.nxtbookMEDIA.com