HomeMy WebLinkAbout2006 11 13 Regular 300 Dyson Drive
COMMISSION AGENDA
ITEM 300
REGULAR
November 13, 2006
Meeting
Authorization
REQUEST: Public Works requesting the City Commission to consider a second straw
ballot for the proposed Dyson Drive traffic calming project.
PURPOSE: The purpose of this agenda item is to request the City Commission to consider a
second straw ballot for the proposed Dyson Drive traffic calming project
PROJECT CHRONOLOGY:
April 21, 2005 - A public meeting was held at City Hall regarding the proposed Dyson Drive
sidewalks. All property owners abutting Dyson Drive in the City were invited to the meeting.
The residents' primary concerns expressed at the public meeting were tree impacts, drainage, and
the need for traffic calming.
May 9, 2005 - The City Commission reviewed the feedback from the public meeting and
directed staff to modify the design to incorporate traffic calming and to address tree impacts.
June 27, 2005 - The City Commission reviewed the recommendations of the City's traffic
engineering consultant, Ian Lockwood, P.E. from Glatting Jackson, and directed Staff to proceed
with the design incorporating traffic calming and modifications to the sidewalk alignment The
Commission authorized an appropriation of $25,000 to have the design updated.
February 20, 2006 - The City Commission held a public hearing for the project to present the
updated design and obtain feedback from the residents. The Commission directed Staff to
conduct a straw ballot of all property owners who live within the two-mile radius of Rainbow
Elementary that would conceivably use one of the proposed routes to walk to Rainbow
Elementary. Based on this direction, Staff identified a total of 161 properties to be included in
the straw ballot
March 3, 2006 - The straw ballots were mailed to 161 property owners with a required return
date of March 17, 2006. The straw ballot identified three options for the project based on the
three funding alternatives available from Seminole County: 1) sidewalks and traffic calming; 2)
111306_COMM_Regular_300_Dyson Drive Traffic Calming
Regular Agenda Item 300
November 13,2006
Page 2
just sidewalks with no traffic calming; and 3) no sidewalks and no traffic calming. A total of 100
ballots were received, with results as follows:
APPROVE SIDEWALKS AND TRAFFIC CALMING:
43
Ballot Votes
APPROVE SIDEWALKS, BUT REJECT TRAFFIC CALMING:
17
Ballot Votes
REJECT SIDEWALKS AND TRAFFIC CALMING:
38
Ballot Votes
Incomplete:
2'
Ballot Votes
April 10, 2006 - The straw ballot results were presented to the Commission. The Commission
approved both the sidewalks and the traffic calming on Dyson Drive.
July 24, 2006 - The Commission approved an Interlocal Agreement with Seminole County that
provides the City funding up to $1,000,000 for sidewalk and traffic calming projects in the City,
including the sidewalks and traffic calming on Dyson Drive.
September 30, 2006 - The final Dyson Drive design documents, including the sidewalks and
traffic calming, were released by the City to a Seminole County continuing sidewalk construction
contractor for pricing.
CONSIDERATIONS:
At the October 9,2006 City Commission meeting, the Commission directed Staff to draft a
second straw ballot to specifically address the proposed traffic calming on Dyson Drive. A copy
of the draft straw ballot and the project information sheet are included as Attachment 1.
ADDITIONAL DESIGN CONSIDERATIONS:
Median Width
The current design consists of 5-foot wide median islands with 2.34-foot wide landscape areas,
9.5-foot wide travel lanes (lO.O-feet to face of curb), and a 12-inch concrete ribbon curb at the
roadway outer edge. The medians were originally 6-feet wide with 2.84-foot wide landscape
areas and 9.0-foot wide travel lanes. The medians were narrowed to 5-feet based on the
Commission's direction at the February 20,2006 public hearing.
Staff has recently reviewed various median design options with the engineer-of-record in order to
maximize the landscape area width while still providing sufficient travel lane widths. Staff
recommends using a "Type B" mountable curb at the medians, which would eliminate the 6"
gutters and widen the landscape area to 3.5-feet while maintaining 9.5-foot wide asphalt travel
lanes.
111306_ COMM _Regular _300_ Dyson Drive Traffic Calming
Regular Agenda Item 300
November 13,2006
Page 3
The photograph below shows Staffs field testing performed in December 2005 with a large
single-unit truck with 9.0-foot wide trave11anes and a 6.0-foot wide median represented by the
cones in the road. This testing indicated that large single-unit trucks could comfortably travel
along the 9.0-foot wide travel lanes. In addition, the photo does not show the proposed 12" wide
concrete ribbon curbs that would be located along the outer edge of the roadway pavement at the
median islands.
AL TERNA TIVE TRAFFIC CALMING OPTIONS:
The following traffic calming devices were evaluated by PBS&J for Seminole County in the
"Dyson Drive Traffic Calming Study" prepared in July 2003:
. Speed Humps - a slightly raised (2" - 3.5") area crossing the trave11anes.
. Speed Tables - a raised median in the center of the roadway,
. Traffic Circles - an elevated area in the center of the intersection that generally provides
counter-clockwise traffic flow.
. Roundabouts - a larger version of a traffic circle, generally having channelization islands
and a higher throughput capacity.
. Mid-Block Chokers - a physical curbside constriction that narrows the travel lanes.
. Chicane - a device that forces drivers to negotiate an "s" shaped travel path using
alternating curbside channelization.
. Bu1bout - a narrowing of the street width, generally at intersections creating a shorter and
safer pedestrian crossing and encourages drivers to slow down.
. Median Islands - an elevated area in the middle of the roadway, often with a curb section.
111306_COMM_Regular_300_Dyson Drive Traffic Calming
Regular Agenda Item 300
November 13,2006
Page 4
Traffic calming devices generally work better when multiple devices are used in coordination
along a roadway. PBS&J recommended the usage of traffic circles and median islands. As noted
in PBS&J's report, the median islands can be more effective at reducing cut-through volumes
than reducing speeds, although some installations have had excellent results. Traffic circles are
effective at reducing speeds but have a limited effect on traffic volumes. For this reason and due
to the site specific conditions along Dyson Drive, the traffic circles and median islands were
recommended.
Please refer to Attachment 2 for detailed information on various traffic calming devices and their
effectiveness.
Please refer to Attachment 3 for an article by David Clark, P.E., comparing all-way stops to
speed humps in a Georgia suburb. The article concludes that "all-way stops have a very limited
area of influence immediately around the stop sign location before vehicles actually increase their
speeds to a rate that is faster than before the all-way stops were installed."
STAFF RECOMMENDATION:
Staff recommends that the Commission review the enclosed information and provide direction
regarding a possible straw ballot.
ATTACHMENTS:
1. Attachment 1 - Draft Straw Ballot and Traffic Calming Information Sheet
2. Attachment 2 - Information on Various Traffic Calming Measures and their Effectiveness
3. Attachment 3 - Article by David Clark, P.E. comparing all-way stops to speed humps
COMMISSION ACTION:
111306_ COMM _Regular _300_ Dyson Drive Traffic Calming
ATTACHMENT NO.1
NOTICE
PROPOSED DYSON DRIVE
TRAFFIC CALMING IMPROVEMENT PROJECT
STRAW BALLOT
Dear Residents:
Due to concerns raised by some residents in the Dyson Drive area, the Winter Springs City
Commission is requesting additional input on the proposed Dyson Drive Traffic Calming
Improvement Project, which will consist of two (2) mini-traffic circles at the intersections of Dyson
Drive and Morgan Street and Pinto Court and nine (9) curbed and landscaped medians along the
length of Dyson Drive. The City Commission requests your participation through a second straw
ballot which is attached to this page.
The Dyson Drive Traffic Calming Improvement Project is designed to improve traffic safety on
Dyson Drive by constructing the aforementioned mini-traffic circles and medians on Dyson Drive to
reduce the chronic speeding on Dyson Drive. This will further increase the safety of pedestrians
utilizing the new sidewalks that have already been approved and scheduled for installation and help
reduce the likelihood of traffic accidents on Dyson Drive, particularly at intersections.
Additional information regarding the Dyson Drive Traffic Calming Improvement Project is contained in
the Project Information Sheet, which is also attached to this page. Furthermore, a general Sketch
Rendering of the traffic calming improvements (mini-traffic circles and medians) is attached to this
page.
The Commission will heavily weigh the public response to this non-binding straw ballot. However, the
Commission retains the right to make their final decision based upon the results of the straw ballot
and other forms of information that has been received by the Commission.
Please cast your vote regarding the Dyson Drive Traffic Calming Improvement Project by
marking the ballot and returning it in the enclosed prepaid envelope. In order to be counted,
the ballot envelope must be postmarked no later than
If you need any additional information after reviewing the Project Information Sheet and depiction,
please contact the City Engineer, Brian Fields. P.E., at 407-327-7597.
Thank you for your participation in the proposed Dyson Drive Traffic Calming Improvement Project.
Sincerely,
Ronald W. McLemore
City Manager
City of Winter Springs
1126 E. State Road 434
Winter Springs, Florida 32708
NON-BINDING STRAW BALLOT
BALLOT
CITY OF WINTER SPRINGS
DYSON DRIVE
TRAFFIC CALMING IMPROVEMENT PROJECT
THIS PROJECT IS BEING FUNDED BY SEMINOLE COUNTY
AT NO COST TO THE CITY OF WINTER SPRINGS' RESIDENTS
. INSTRUCTIONS: TO VOTE, COMPLETELY FILL IN THE SQUARE NEXT TO YOUR CHOICE. . Use
a permanent marking device such as an ink pen. . Voters are encouraged to read the Dyson
Drive Traffic Calming Improvement Project Information Sheet and Sketch Rendering before
casting their vote.
The ballot envelo e must be ostmarked no later than
MARK BALLOT HERE
D I SUPPORT THE DYSON DRIVE TRAFFIC
CALMING IMPROVEMENT PROJECT
D I OPPOSE THE DYSON DRIVE TRAFFIC
CALMING IMPROVEMENT PROJECT
NON-BINDING BALLOT
Notes:
1. All returned straw ballots must be Printed Name
original ballots (no photocopies)
with an original signature in order
to be valid.
Date
Signature Of Property Owner
2. Only one ballot per property
address will be accepted.
Address
PROJECT INFORMATION SHEET
PROPOSED DYSON DRIVE TRAFFIC CALMING
Why is traffic calmina proposed on Dyson Drive?
Traffic calming is an effective tool for reducing speeding.
Seminole County conducted a traffic calming and speed
study on Dyson Drive, which determined that the
average speed was 31.6 mph westbound and 28.9 mph
eastbound, and the 85th percentile speeds were 33.8
mph westbound and 38.0 mph eastbound. An 85th
percentile speed of 38.0 mph means that 15% of the
drivers in the eastbound direction were recorded at
speeds greater than 38.0 mph. The posted speed limit
on Dyson Drive is 25 mph.
What is the proposed traffic calmina proiect?
The proposed traffic calming consists of mini-traffic
circles at the intersections of Dyson Drive with Morgan
Street and Pinto Court, and the installation of median
islands at various locations along Dyson Drive.
What are mini-traffic circles?
The mini-traffic circles are 16-foot diameter curbed
circles located in the center of the intersection. The
circles will be landscaped and will have appropriate
signage and striping to ensure safe operation for
motorists and pedestrians. Traffic circles reduce vehicle
speeds, accident rates, injuries, and traffic volumes.
Can large trucks use the mini-traffic circles?
Field testing has been performed for the proposed traffic
circles to verify that the circles would safely operate as
intended for large single-unit trucks. As with most traffic
circles, oversized multi-unit vehicles such as tractor-
trailers have to use caution when making left turns, as
they will likely need to make immediate left turns rather
than proceeding counterclockwise around the circle as
all other vehicles would.
What are the median islands?
The median islands consist of 5-foot wide curbed
medians with lengths up to 40-feet located in the center
of the road. The medians will be landscaped with
ground cover and relatively short vegetation. A total of
nine (9) medians are proposed at various locations along
Dyson Drive. The medians do not block access to any
driveways or intersections, and they will be striped and
reflectorized to clearly identify them to motorists. The
medians reduce unobstructed roadway sight lines that
contribute to speeding, and they reduce lane widths (in
this case from 12-feet to 9.5-feet), which also helps to
slow vehicles down.
Why am I beina asked to complete this straw ballot?
The Winter Springs City Commission authorized this
straw ballot at the October 23, 2006 Commission
Meeting in order to gain additional information specific to
the traffic calming portion of the Dyson Drive project.
Won't drivers crash into the traffic circles and
median islands?
Both the traffic circles and median islands will be signed,
striped, and reflectorized to make them highly visible to
all motorists. The median islands will have an outer curb
and inner landscaped area consisting mainly of trees
and shrubs. The median islands do not restrict access
to any driveways. The traffic circles will be signed and
striped to facilitate counterclockwise movement within
the circle, and they will also have an outer mountable
curb that can withstand vehicle loads if driven over.
Would stop siqns provide better traffic calminq?
No, stop signs are not traffic calming devices. Stop
signs only slow vehicles down in the immediate vicinity
of intersections, whereas traffic circles are part of a
series of devices along the entire corridor that
collectively create an environment less favorable to
speeding.
What is the status of the proposed sidewalks?
The Dyson Drive sidewalks are approved and scheduled
to begin construction in the near future. This straw ballot
concerns only the traffic calming portion of the project.
Who is payina for this proiect?
Seminole County has funded the entire project through
an Interlocal Agreement with the City of Winter Springs.
The City cannot utilize the County funds for any other
purposes.
Where can I qet additional information?
If you have any questions, please contact the City
Engineer, Brian Fields, P.E., at 407-327-7597 or
bfields@winterspringsfl.org. The design drawings are
available for viewing on the City website:
www.winterspringsfl.org, under "Public Notices."
DYSON DRIVE - TYPICAL MEDIAN AND TRAFFIC CIRCLE DETAILS
DYSON DRIVE TRAFFIC CALMING PLAN
DYSON DR
WINTER SPRINGS
SEMINOLE CO.
. Proposed Mini Traffic Circle
- Proposed Media Island
TrafficCalming.org - brought to you by Fehr & Peers
Effectiveness of Traffic Calming Measures...
Speed Impacts of Traffic Calming Measures
(standard deviations in parentheses)
Sample Size 85th Percentile Speed Average Change in 85th Average % Change
Afterward Percentile Speed
12' Speed Hump 179 27.4 mph -7.6 mph -22%
(4.0 mph) (3.5 mph) (9%)
14' Speed Hump 15 25.6 -7.7 -23
(2.1) (2.1 mph) (6)
22' Speed Table 58 30.1 -6.6 -18
(2.7) (3.2) (8)
Longer Table (>22') 10 31.6 -3.2 -9
(2.8) (2.4) (7)
Raised Intersection 3 34.3 -0.3 -1
(6.0) (3.8) (10)
Traffic Circle 45 30.3 -3.9 -11
(4.3) (3.2) (10)
Narrowing 7 32.3 -2.6 -7
(2.8) (5.5) (22)
Choker 5 28.6 -2.6 -14
(3.1) (1.3) (4)
Half Closure 16 26.3 -6.0 -19
(5.2) (3.6) (11 )
Diagonal Diverter 7 27.9 -1.4 -0
(5.2) (4.7) (17)
Note: speeds are measured at midpoints between measures
Volume Impacts of Traffic Calming Measures
(standard deviations in parentheses)
Sample Size Average Change in Volume Average % Change
-392 vehicles per day -20%
http://www . trafficcalming.org/ effecti veness.html
Page 1 of2
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Page 2 of 2
Choker 5 (384 vehicles per day) (19%)
Full Closure 19 -671 -44
(786) (36)
Half Closure 53 -1611 -42
(2444) (41)
Diagonal Diverter 27 -501 -35
(622) (46)
Other Volume Control 10 -1167 -31
(1781) (36)
Safety Impacts of Traffic Calming Measures
( U.S. Experience)
Number of Observations Average Number of Collisions % Change in Collisions
Before Treatment After Treatment
12' Speed Hump 49 2.7 2.4 -11%
14' Speed Hump 5 4.4 2.6 -41%
22' Speed Table 8 6.7 3.7 -45%
Traffic Circle 17 5.9 4.2 -29%
(w/o Seattle)
Traffic Circle 130 2.2 0.6 -73%
(wi Seattle )
All Measures
wlo adjustments 192 2.6 1.3 -50% *
wi adjustments 42 3.8 3.0 -21%**
* Significant at 0.001 probability level
** Significant at 0.04 probability level
2005 @ Fetlr & Peers. All rights reserved.
http://www.trafficcalming.org/effectiveness.html
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Page 1 of 2
Speed Tables...(trapezoidal humps. speed platforms)
Speed tables are flat-topped speed humps often constructed with brick or other
textured materials on the flat section. Speed tables are typically long enough for the
entire wheelbase of a passenger car to rest on the flat section. Their long flat fields
give speed tables higher design speeds than Speed Humps. The brick or other
textured materials improve the appearance of speed tables, draw attention to them,
and may enhance safety and speed-reduction.
Speed tables are good for locations where low speeds are desired but a somewhat
smooth ride is needed for larger vehicles.
Advantages:
. They are smoother on large vehicles (such as fire trucks) than Speed Humps
. They are effective in reducing speeds, though not to the extent of Speed
Humps
Disadvantages:
. They have questionable aesthetics, if no textured materials are used;
. Textured materials, if used, can be expensive; and
. They may increase noise and air pollution.
Effectiveness:
. For a 22-foot speed table:
o Average of 18% decrease in the 85th percentile travel speeds, or from
an average of 36.7 to 30.1 miles per hour; (from a sample of 58 sites).
o Average of 45% decrease in accidents, or from an average of 6.7 to
3.7 accidents per year (from a sample of 8 sites).
.
Similar Measures:
http://www.trafficcalming.org/speedtables.html
Bellevue, WA . This speed table is entirely asphalt
with parabolic ramps.
Naples, FL - This concrete speed table is combined
with textured pavement to enhance its visibility and
speed-reducing effect.
11/6/2006
TrafficCalming.org - brought to you by Fehr & Peers
. By removing the flat section in the middle, you have a Speed Hump
. By placing a crosswalk on the flat section, you have a Raised Crosswalk
. By raising the level of an entire intersection, you have a Raised Intersection
Cost Estimate(s):
. $2,000-$2,500 (Portland, OR)
. $2,000 (Sarasota, FL)
. $2,000 (Seattle, WA)
http://www . trafficcalming.org/ speedtables.html
Page 2 of2
Portland, OR - This asphalt spped table uses
leading horizontal stripe markings.
Charlotte, NC . This speed table uses stamped,
colored concrete..
2005 !{) Fehr & Peers. All rights reserved.
11/6/2006
TrafficCalming.org - brought to you by Fehr & Peers
Page 1 of2
Speed Humps...(road Humps. undulations)
Speed humps are rounded raised areas placed across the roadway. They are
generally 10 to 14 feet long (in the direction of travel), making them distinct from the
shorter "speed bumps" found in many parking lots, and are 3 to 4 inches high. The
profile of a speed hump can be circular, parabolic, or sinusoidal. They are often
tapered as they reach the curb on each end to allow unimpeded drainage.
Speed Humps are good for locations where very low speeds are desired and
reasonable, and noise and fumes are not a major concern.
Advantages:
. Speed Humps are relatively inexpensive
. They are relatively easy for bicycles to cross if designed appropriately
. They are very effective in slowing travel speeds.
Disadvantages:
. They cause a "rough ride" for all drivers, and can cause severe pain for
people with certain skeletal disabilities
. They force large vehicles, such as emergency vehicles and those with rigid
suspensions, to travel at slower speeds
. They may increase noise and air pollution
. They have questionable aesthetics.
Effectiveness:
. For a 12-foot hump:
o Average of 22% decrease in the 85th percentile travel speeds, or from
an average of 35.0 to 27.4 miles per hour; (from a sample of 179
sites).
o Average of 11 % decrease in accidents, or from an average of 2.7 to
2.4 accidents per year (from a sample of 49 sites).
. For a 14-foot hump:
http://www . trafficcalming.org/ speedhumps.html
Portland, OR - This 14-foot speed hump uses a
chevron marking pattern.
West Palm Beach, FL - This 12-foot hump is
combined with Textured Pavement to enhance its
visibility and speed-reducing effect.
11/6/2006
TrafficCalming.org - brought to you by Fehr & Peers
o Average of 23% decrease in the 85th percentile travel speeds, or from
an average of 33.3 to 25.6 miles per hour (from a sample of 15 sites).
o Average of 41% decrease in accidents, or from an average of 4.4 to
2.6 accidents per year (from a sample of 5 sites).
Similar Measures:
. By lengthening the hump with a flat section in the middle, you have a Speed
Table.
. By tuming an entire crosswalk into a speed hump, you have a Raised
Crosswalk
. By raising the level of an entire intersection, you have a Raised Intersection.
Cost Estimate(s):
. $2,000-$2,500 (Portland, OR)
. $2,000 (Sarasota, FL)
. $2,000 (Seattle, WA)
http://www . trafficcalming.org/ speedhumps.html
Page 2 of2
Ft. Lauderdale, FL - A 22-foot speed hump with zig-
zag markings.
Sacramento, CA - This "speed lump" includes wheel
cut-outs that allow buses and emergency vehicles to
pass without slowing. The cut-outs are spaced too far
apart for passenger vehicles to pass without at least
one set of wheels being affected by the hump.
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Traffic Circles... (rotaries. intersection islands)
Traffic circles are raised islands, placed in intersections, around which traffic
circulates. They are good for calming intersections, especially within neighborhoods,
where large vehicle traffic is not a major concern but speeds, volumes, and safety
are problems.
Advantages:
. Traffic Circles are very effective in moderating speeds and improving safety
. If designed well, they can have positive aesthetic value
. Placed at an intersection, they can calm two streets at once
Disadvantages:
. They are difficult for large vehicles (such as fire trucks) to circumnavigate
. They must be designed so that the circulating lane does not encroach on the
crosswalks
. They may require the elimination of some on-street parking
. Landscaping must be maintained, either by the residents or by the
municipality
Effectiveness:
. Average of 11 % decrease in the 85th percentile travel speeds, or from an
average of 34.1 to 30.2 miles per hour (from a sample of 45 sites)
. Including a large sample from Seattle, an average of 73% decrease in
accidents, or from an average of 2.2 to 0.6 accidents per year (from a sample
of 130 sites)
. Excluding the large sample from Seattle, an average of 29% decrease in
accidents, or from an average of 5.9 to 4.2 accidents per year (from a sample
of 17 sites)
Similar Measures:
http://www.trafficcalming.org/trafficcircles.html
Boulder, CO -This traffic circle is combined with
textured crosswalks. The center island uses low-
maintenance landscaping.
Seattle, WA - This traffic circle is located at a
T-intersection, as indicated by the sign. A truck apron is
included that allows trucks to make a left-turn, while
passenger vehicles are discouraged from using the
truck apron by the short lip at its edge.
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. By placing a raised island in a mid block location, you have a Center Island
Narrowing
. By enlarging the intersection and the center island, inserting splitter islands at
each approach, setting back the crosswalks away from the circulating lane,
and implementing yield control at all approaches, you have a Roundabout
Cost Estimate(s):
. Varies by materials used and the amount of area covered
http://www . trafficcalming.org/trafficcircles.html
Page 2 of2
Ft. Lauderdale. FL - This traffic circle has a larger
truck apron. Splitter islands and yield lines have been
striped at each approach.
Eugene, OR - This traffic circle is controlled by
all-way stop control.
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Roundabouts... (rotaries)
Roundabouts require traffic to circulate counterclockwise around a center island.
Unlike Traffic Circles, roundabouts are used on higher volume streets to allocate
right-of-way between competing movements.
Good for:
. Locations with a history of accidents;
. Intersections where queues need to be minimized
. Intersections with irregular approach geometry
. Providing inexpensive-to-operate traffic control as an alternative to a traffic
signal
· Handling a high proportion of U-turns
. Locations with abundant right-of-way
Advantages:
. Roundabouts can moderate traffic speeds on an arterial
. They are generally aesthetically pleasing if well landscaped
. They enhanced safety compared to traffic signals
. They can minimize queuing at the approaches to the intersection
. They are less expensive to operate than traffic signals
Disadvantages:
. They may be difficult for large vehicles (such as fire trucks) to circumnavigate
. They must be designed so that the circulating lane does not encroach on the
crosswalks
. They may require the elimination of some on-street parking
. Landscaping must be maintained, either by the residents or by the
municipality
Effectiveness:
http://www . trafficcalming.org/roundabouts.html
Beaverton, OR - This roundabout includes a fully
landscaped center island and splitter islands. The
splitter island helps to guide approaching traffic onto
a counterclockwise path around the center island, but
the angle shouldn't be so sharp as to require drivers
to crane their necks.
Tallahassee, FL - Here a bicyclist waits for an
approaching car to pass before entering the
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. Average 29% reduction in accidents, with a reduction from 9.3 to 5.9
accidents per year (from a sample of 11 sites; source: Roundabouts: An
Informational Guide).
Similar Measures:
. By constructing a small island in a neighborhood intersection and leaving the
existing curbs, you have a Traffic Circle
Cost Estimate(s):
. Varies by materials used and the amount of area covered
http://www . trafficcalming.org/roundabouts.html
Page 2 of2
roundabout. Bicycle treatment at roundabouts can
happen in either of two ways: they can be encouraged
to "take the lane" and travel on the circulating lane with
motor vehicles, or they can be guided onto the
sidewalks and encouraged to use the crosswalks..
West Palm Beach, FL - This roundabout
demonstrates the setback of the crosswalk from the
circulating lane. This setback should allow at least
one car to be able to pass the crosswalk and wait
safely before entering the circulating lane once an
adequate gap occurs.
Summerville, NV - This roundabout has a wide,
multilane approach, but with the markings faded,
these lanes are somewhat ambiguous
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Neckdowns... (nubs. bulbouts, knuckles. intersection narrowings. corner buldges. safe crossesJ
Neckdowns are curb extensions at intersections that reduce the roadway width from
curb to curb. They "pedestrianize" intersections by shortening crossing distances for
pedestrians and drawing attention to pedestrians via raised peninsulas. They also
tighten the curb radii at the comers, reducing the speeds of turning vehicles.
They are good for intersections with substantial pedestrian activity and areas where
vertical traffic calming measures would be unacceptable because of noise
considerations.
Advantages:
. Neckdowns improves pedestrian circulation and space
. Through and left-turn movements are easily negotiable by large vehicles
. They create protected on-street parking bays
. They reduce speeds, especially for right-turning vehicles
Disadvantages:
. Effectiveness is limited by the absence of vertical or horizontal deflection
. They may slow right-turning emergency vehicles
. They may require the elimination of some on-street parking near the
intersection
. They may require bicyclists to briefly merge with vehicular traffic
Effectiveness:
. Average of 7% decrease in the 85th percentile travel speeds, or from an
average of 34.9 to 32.3 miles per hour (combined average for various
narrowing measures, taken from a sample of 7 sites)
Similar Measures:
http://www.trafficca1ming.org/neckdowns.htm1
Eugene, OR . This neckdown is combined with a
Raised Crosswalk.
Cambridge, MA - These neckdowns slow vehicles
approaching a bay of on-street parking.
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. $40,000 - 80,000 for four corners
. If a roadway is narrowed at a midblock location, you have a Choker
. Can be easily combined with a Raised Intersection
Cost Estimate(s):
Jacksonville, FL - This neckdown are combined with
a raised. textured Intersection.
Sarasota, FL . This neckdown is used to protect a
crosswalk.
2005 @ Fehr & Peers, All rights reserved,
http://www . trafficcalming.org/neckdowns.html
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Center Island Narrowings... (midblock medians. median slowpoints. median chockersJ
A center island narrowing is a raised island located along the centerline of a street
that narrow the travel lanes at that location. Center island narrowings are often
landscaped to provide a visual amenity. Placed at the entrance to a neighborhood,
and often combined with textured pavement, they are often called "gateway islands."
Fitted with a gap to allow pedestrians to walks through at a crosswalk, they are often
called "pedestrian refuges."
Center Island Narrowings are good for entrances to residential areas, and wide
streets where pedestrians need to cross.
Advantages:
. Center Island Narrowings increase pedestrian safety
. If designed well, they can have positive aesthetic value
. They reduce traffic volumes
Disadvantages:
. Their speed-reduction effect is somewhat limited by the absence of any
vertical or horizontal deflection
. They may require elimination of some on-street parking
Effectiveness:
. Average of 7% decrease in the 85th percentile travel speeds, or from an
average of 34.9 to 32.3 miles per hour (combined average for various
narrowing measures, taken from a sample of? sites)
Similar Measures:
. If a roadway is narrowed out from the curbs at an intersection, you have a
Neckdown
http://www.trafficcalming.org/centerislandnarrowrings.html
Montgomery County, MD. This center island
narrowing is somewhat long. Visible on the pavement
is the previous centerline before it was angled to
guide motorists to the right of the island.
Portland, OR - This center island narrowing is
combined with two crosswalks.
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. $8,000 - 15,000 (Portland, OR), $5,000 (Sarasota, FL)
Cost Estimate(s):
Portland, OR . This center island narrowing has
hardscape but minimal live landscaping, minimizing
maintenance costs.
Ft. Lauderdale, FL . This center island narrowing is
combined with Textured Pavement to provide a
geway measure.
2005 @ Fehr & Peers. All rights reserved.
http://www . trafficcalming.org/ centerislandnarrowrings.html
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Chokers... (pinch points. midblock narrowings. midblock yieldpoints. constrictions)
Chokers are curb extensions at mid block locations that narrow a street by widing the
widewalk or planting strip. If marked as crosswalks, they are also known as safe
crosses. Two-lane chokers leave the street cross section with two lanes that are
narrower than the normal cross section. One-lane chokers narrow the width to allow
travel in only one direction at a time, operating similarly to one-lane bridges. They are
good for areas with substantial speed problems and no on-street parking shortage.
Advantages:
. Chokers are easily negotiable by large vehicles (such as fire trucks)
. If designed well, they can have positive aesthetic value
. They reduce both speeds and volumes
Disadvantages:
. Their effect on vehicle speeds is limited by the absence of any vertical or
horizontal deflection
. They may require bicyclists to briefly merge with vehicular traffic
. They may require the elimination of some on-street parking
Effectiveness:
. Average of 7% decrease in the 85th percentile travel speeds, or from an
average of 34.9 to 32.3 miles per hour (combined average for various
narrowing measures, taken from a sample of 7 sites)
Similar Measures:
. If a roadway is narrowed at an intersection, you have a Neckdown
. If a roadway is narrowed from the centerline, rather than from the curbs (i.e.
using a raised island), you have a Center Island Narrowing
http://www . trafficcalming.org/ chokers.html
Winter Park, FL - This choker is combined with a
crosswalk, creating a safe cross.
Montgomery County, MD - This choker uses slightly
offset curb extensions to accommodate the residential
driveways.
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. $7,000 - 10,000 (Portland, OR)
Cost Estimate(s):
Howard County, MD - This is a one-lane choker.
Vehicles on one side yield to vehicles from the other
side until the queue is cleared, just as on one-lane
bridges.
Sarasota, FL - This choker includes a yield line to
alert approaching vehicles.
2005@ Fehr & Peers. All rights reserved.
http://www . trafficcalming.org/ chokers.html
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Chicanes... (deviations. serpentines. reversing curves. twists)
Chicanes are curb extensions that alternate from one side of the street to the other,
forming S-shaped curves. Chicanes can also be created by alternating on-street
parking, either diagonal or parallel, between one side of the street and the other.
Each parking bay can be created either by restriping the roadway or by installing
raised, landscaping islands at the ends of each parking bay.
Good for locations where speeds are a problem but noise associated with Speed
Humps and related measures would be unacceptable.
Advantages:
. Chicanes discourage high speeds by forcing horizontal deflection
. They are easily negotiable by large vehicles (such as fire trucks) except
under heavy traffic conditions
Disadvantages:
. They must be designed carefully to discourage drivers from deviating out of
the appropriate lane
. Curb realignment and landscaping can be costly, especially if there are
drainage issues
. They may require the elimination of some on-street parking
Effectiveness:
. No data has been compiled on the effects of chicanes
Similar Measures:
. By placing the edge islands opposite each other (without staggering them),
you have a Choker
http://www . trafficcalming.org/ chicanes.html
Seattle, WA - These chicane islands extend out to
the roadway centerline, creating a highly deviating
path.
Alachua, FL - These curb extensions protect
alternating diagonal parking bays.
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. $14,000 (Sarasota, FL)
Cost Estimate(s):
Tallahassee, FL - The chicane in this case consists
of a series of changing angles, rather than a
continuously curving path.
Montgomery County, MD . Here is a one-way
chicane, created by a deviating curb-and-gutter.
2005 () Fehr & Peers. All rights reserved.
http://www . trafficcalming.org/ chicanes.html
11/612006
ATTACHMENT NO. 3
All-Way Stops Versus Speed Humps: Which is more effective at
slowing traffic speeds?
David E. Clark, P.E.
Abstract
Athens-Clarke County, Georgia (population 96,500) established the Neighborhood Traffic
Management Program (NTMP) in 1997 to address the growing request by neighborhoods to
reduce traffic speeds and volumes on residential streets. Although one of the desired outcomes
of the NTMP was to limit the number of requests for unwarranted all-way stop signs throughout
neighborhoods, several neighborhoods continued to request additional stop signs to be installed
to be used as speed control devices.
Of particular interest were two residential streets that were similar in character and whose
residents approached Traffic Engineering in 1998 to request measures to be taken to control the
speed of traffic traveling through the neighborhood. The first street, Auburn Parkway, requested
a series of speed humps be installed on the street. While, the second street, Holman Avenue,
requested all-way stops be placed at several intersecting streets.
Athens-Clarke County used these two requests as an opportunity to collect data comparing these
different techniques to control traffic speeds. Traffic Engineering focused data collection and
traffic monitoring efforts in this neighborhood during a two-year period before and after the
devices and stop signs were installed. Specifically, this data was used draw any definitive
conclusions about the effectiveness of these devices on controlling speeds in the neighborhood
for use with future requests.
Based on the results of the study, Traffic Engineering determined that all-way stops have a very
limited influence area around the stop sign before vehicles actually increase their speeds to a
level that is faster than before the all-way stops were installed. Whereas the speeds on the streets
that have traffic-calming devices are much more constant and are only slightly higher than the
posted speed limit.
The paper summarizes the data collected, speed and volume trends observed, observed results in
the neighborhoods, and recommendations for additional research.
Introduction
Most traffic engineers receive their fair share of requests from citizens to install more all-way
stop conditions on streets to control speeds and provide for a "more neighborhood feeling"
environment. Whereas the MUTCD has published very clear guidelines in identifying the
conditions when to install these devices and recent research has focused on whether the warrants
are valid, there has been little research done as to the impact these all-way stops have on speeds
through neighborhoods.
In 1997, Edward Cline of Willdan Associates published findings from a study preformed in Long
Beach, California documenting how effective all-way stops were as speed deterrents in
residential areas. Their findings indicated that speeds were almost identical after the installation
of the stop signs along the corridor. However, during the course of their study, speeds were
collected 250 feet away from the stop signs. Athens-Clarke County was interested in furthering
this study by determining if stop signs were effective at any point along the corridor; in addition,
the comparison of the speed profiles on streets with speed humps was of interest.
Therefore, two similar developed streets were chosen to initiate a data collection effort. Holman
Avenue was a street that recently requested additional all-way stops at some intersections in the
neighborhood; while Auburn Parkway requested speed humps as a speed-control measure.
Roadwav Descriptions
Holman Avenue
Holman Avenue is a residential street surrounded by 1960's style homes with on-street parking
but with no sidewalks. The curb-to-curb width of the street is 30 feet with no centerline or other
pavement markings. The roadway is perpendicular to two arterial streets and is approximately a
mile long. The character of the street traffic is primarily residential traffic from the surrounding
residents but has some cut-through traffic. Within the study area there are five cross streets, two
of which had existing all-way stop conditions located at approximately 900 feet apart.
Auburn Parkway
Auburn Parkway is residential street surrounded by late 1970's and early 1980's homes with no
sidewalks and the homes are setback further from the roadway than Holman Avenue. Auburn
Parkway does not have any curbs and the pavement width is approximately 28 feet. The
roadway is approximately 2,000 feet long and is one of two principle main residential roadways
into a large subdivision with over 200 homes. All of the traffic on this roadway originates from
the residential neighborhood. Within the study area there are four cross streets, all of which have
two-way stop control conditions for the side streets.
Speed and volumes observed
Traffic volumes and speeds were collected using a variety of common methods including rubber-
tube traffic counters, radar guns, time-distance measurements, and field observations. Traffic
information was collected throughout the corridor, including at midblock locations, 35 feet and
150 feet from intersections (both stop-controlled and no control), and at intersections themselves.
Data was collected immediately before the installation of the requested devices and nine months
after their installation. Not surprisingly the speeds varied quite a bit along both corridors, and the
following tables reflect averages that were observed in corridor during the study.
Ran e of 85t Percentile Seeds
10 mph Pace
Acceleration/Deceleration Rates
near All-Way Stop Location
Dail Volume
Holman Avenue Traffic Characteristics
Before All-Wa Sto
7.5 to 38.8 m h
18 - 27 mph
+2.2 ftls
- 1.6 ft/s2
1,100 d
After All-Wa Sto
7.5 to 35.0 m h
17 - 26 mph
+3.8 ftls
-4.5 ftls2
1,055 d
The speed data was collected throughout the corridor and is reflected in the following graphs.
Speed Profile Along Holman Before Holman/Price All-Way Stop
1950 2150 2350 2550 2750 2950
Distance from Oglelhorpe Avenue C:=J Area of Influence
- - - Before 4-Way Stop @ Price - After 4-Way Stop @ Price
Auburn Parkway Traffic Characteristics
Before Seed Humps After Speed Humps
28.0 to 37.4 m h 18.7 to 29.7 m h
25 - 34 m h 17 - 26 m h
+0.9ft1s +1.7ft1s
-1.1 ftls2 -2.0 ft/s2
900 d 900 d
45
Speed Profile Along Speed Humps
40
35
Distance from Riverbottom
- - - Before Speed Humps -After Speed Humps
Observed results and conclusions
Based on the data collected and field observations near and around the unwarranted all-way stop
location, Traffic Engineering staff determined that all-way stops have a very limited area of
influence immediately around the stop sign location before vehicles actually increase their
speeds to a rate that is faster than before the all-way stops were installed. Based on the
observations in Athens-Clarke County, this area of influence is estimated to be no more than 200
feet around the intersection (approximately 100 feet before and after the stop sign.)
Furthermore, the installation of a stop sign does not seem to influence driver behavior outside of
the 200-foot area of influence.
This compares to the traffic characteristics on Auburn Parkway where the data indicates that the
speeds are more constant on the streets that have traffic calming devices. In addition, the 85th
percentile speed is only slightly higher than the posted speed limit on those with speed humps.
This is contrasted with the condition on the all-way stop corridor where the 85th percentile speed
is more than 10 mph over the posted speed.
The data collected along the corridor suggests that the addition of another stop sign on Holman
Avenue had no impact on speeds on any other block section along Holman Avenue. Further
demonstrating the very small area of influence that all-way stops seem to have on driver
behavior.
Not surprisingly, the acceleration and deceleration rates of vehicles at the all-way stop are much
more dramatic than the rates observed approaching and leaving the speed humps. In fact,
throughout the corridor the acceleration and deceleration rates along the entire corridor with stop
signs are more pronounced than those along the corridor with speed humps. Again,
demonstrating how speed humps result in more constant speeds on the roadway.
Worrisome to the study, was the fact that the 85th percentile speed through an unwarranted stop
sign was approximately 5 - 7 mph. Whereas some residents argue that "at least the stop signs are
slowing vehicles down," the blatant disregard to the stop sign is believed to be carried on to other
stop controlled locations by drivers where it is imperative for the stop sign be 100 percent
observed. Therefore, it is Traffic Engineering's opinion that unwarranted all-way stop signs
encourage drivers to selectively choose when to observe regulatory signs.
Data along both corridors was recollected two-years after implementation of the all-way stop and
the speed humps and confirmed that the traffic characteristics very similar to the data collected
nine-months after implementation.
Finally an interesting side note highlighting the lack of effectiveness of all-way stop signs can be
demonstrated by the fact that the Holman Avenue residents have now requested traffic calming
devices be installed on the street.
Recommendations for further research
Athens-Clarke County feels that this study provides a starting point for better showing residents
how exactly the installation of an unwarranted, all-way stop intersection impacts traffic and
vehicle speeds. However, there are elements of the study that Athens-Clarke County recognizes
the need for additional study before any definite conclusions can be drawn.
First and foremost, the analysis focused primarily on two streets. Athens-Clarke County
recommends that at least five streets with unwarranted all-way stop signs be compared to those
streets with traffic calming devices. Fortunately, since the full implementation of the
Neighborhood Transportation Management Program in 1998 in Athens-Clarke County the
number of requests for all-way stops have dramatically been reduced. Therefore, data may need
to be collected in surrounding communities.
During the study, the stop signs were position 700 and 1000 feet apart. In areas where stop signs
could be located on a more frequent basis, the area of influence may be larger. Further research
should determine the distance between stop signs which has the most impact on driver behavior
with respect to speed control.
Finally, one aspect of the study that was not considered was accident history and pedestrian
safety with respect to all-way stops. Future studies should consider how all-way stops impact
accident frequency since other research suggests that accident rates may actually increase with
unwarranted stops.
Author Information
David E. Clark, P.E., Member ofITE, Director of Transportation and Public Works, Athens-
Clarke County, P.O. Box 1868, Athens, GA 30603. (706) 613-3440 (voice) (706) 613-3444 (fax)