Table of Contents
Introduction…………………………………………………………..2
Design Considerations……………………………………………….2
Vertical Deflections………………………………………………......5
Raised Crosswalk and Raised Intersection……………………5
Sidewalk Extension……………………………………….. …9
Textured Crosswalk…………………………………………..11
Speed Hump…………………………………………………..11
Horizontal Deflections……………………………………………….13
Chicane………………………………………………………..13
Lateral Shift…………………………………………...16
Curb Extension……………………………………………......16
Center Island Narrowing……………………………...19
Curb Radius Reduction……………………………………….19
Neckdown ……………………………………………21
Choker……………………………………………......21
On-Street Parking…………………………………………….22
Raised Median Island………………………………………...24
Traffic Circle…………………………………………………25
Roundabout………………………………………......28
Obstructions………………………………………………………...29
Directional Closure…………………………………………..29
Diverter……………………………………………………....32
Full closure…………………………………………………..35
Intersection Channelization……………………………….....37
Median through an Intersection……………………………...39
Right In/Right Out Island…………………………………....41
Traffic Calming Signs……………………………………………...43
Signs………………………………………………………....43
Speed Hump sign………………………………………….....43
Traffic Calmed-Neighbourhood sign………………………...44
Appendix A………………………………………………………….45
Glossary……………………………………………………………..46
Bibliography………………………………………………………. .48
1
Design Guidelines for Traffic Calming Measures
Introduction
The purpose of this guide is to standardize the design procedures of traffic
calming measures wherever possible in order to ease the implementation of effective
traffic calming strategies in communities throughout North America. The information
contained in this guide is not a strict set of standards because of certain instances where
specifications may not be able to be met. The specifications presented are optimal, based
on various research projects throughout North America, and should be used wherever it is
possible and feasible to do so.
Design Considerations
There are many general considerations that need to be addressed when designing
any traffic calming measure.
 Grades: Maximum and minimum grades are put into place in order to minimize
vehicle damage, loss of vehicle control, and reduce potential road or property
maintenance due to problems such as poor drainage that could arise from traffic
calming measures. An example of a minimum grade is raised crosswalks or
raised intersections having at least a 1% cross slope for drainage purposes.
Maximum grade must be considered when looking at implementing a vertical
deflection on a sloped road. For example, the maximum grade for implementing
a speed hump is 8%; anything more than this is thought to be potentially
hazardous to a driver because of the high transition slope between the speed
hump and the road.
 Long wheelbase and Emergency Vehicles: Knowledge of emergency vehicle
routes and primary street usage must be acquired before implementing certain
traffic calming measures because of the large turning radii of these vehicles.
Many horizontal street calming measures such as traffic circles, chicanes, lateral
shifts, and directional closures can be impassable for certain large vehicles, and
therefore should be limited to residential use. Another option to accommodate
large vehicles is using a mountable rolled curb around the perimeter of the
horizontal measure.
 Ease of Passage for Other Street Users: Any traffic calming measure which
sacrifices the safety and general use of the street to cyclists or pedestrians should
not be implemented. Compatibility of street calming measures to other street
users can often be accomplished fairly easy. For example, when implementing a
speed hump, passage for bicycles can be obtained by leaving sufficiently wide
gaps in the speed hump near the side of the street. Similarly, any street closure
should include a walkway or path so it is still possible for pedestrians to access
the neighbouring street.
2



Surface Drainage: Surface Drainage is an important design consideration on
both roadways and sidewalks because of the potential problems it can create for
both the road and sidewalk condition, and also the safety of their users. All
traffic calming fixtures should have a minimum cross-slope grade in order to
promote drainage and reduce ponding or ice patches. On roadways with traffic
calming measures that do not have drainage gaps, catch basins must be located at
a higher elevation than the traffic calming measure if there is any grade to the
roadway.
Access to Underground Utilities: Whenever implementing a street calming
measure, the accessibility of underground utilities must be ensured (Skene, Pg.
4-1 – 4-2).
Desired Vehicle Speed: The desired vehicle speed through a traffic calmed area
must be determined before the exact design dimensions of the traffic calming
device can be specified. For horizontal traffic calming measures, the smaller the
turning radius is, the slower the traffic will pass through the area. A formula
from mechanics is used to relate the turning radius to the velocity of the vehicle.
R=V2
15 (e + f)
R
Maximum horizontal radius of the curve (ft)
V
Velocity of the vehicle around the curve (mph)
e
Superelevation rate
f
Side friction factor
The superelevation rate is negligible in almost all urban areas. The side-friction
factor is based on safety against skidding and level of discomfort, and can be determined
from graphs and tables in the American Association of State Highway and Transportation
Officials (AASHTO) “A Policy on Geometric Design of Highways and Streets”. The
calculations of the curve radius apply only to single curves. They can only be used as
general approximations for horizontal traffic calming measures involving more than one
turn such as chicanes and traffic circles.
For vertical traffic calming measures such as speed humps, another mechanics
formula can be used to calculate the centrifugal acceleration over a circular hump of a
given radius.
A
Acceleration (ft/sec2)
A = 2.15 V 2
V
Velocity of vehicle over hump (mph)
R
R
Radius of hump (ft)
Constant Conversion Factor
International traffic calming standards suggest that a vertical acceleration of up to
1 g (32.2ft/sec2) can be tolerable for short periods, however this is fairly high so
3
personal discretion may be used to determine an appropriate sized speed hump
(Ewing, pg. 67 – 69).
 Maintenance: Increased or more difficult street maintenance may occur as a
result of traffic calming. Certain measures should be considered to minimize this
negative effect. Snow plowing over vertical traffic calming elements may cause
damage either to the snow plow or the street. Other traffic calming options or
careful snow plow operating will be necessary to prevent damage on frequently
plowed streets. Accumulation of snow or leaves may also occur as a result of
some traffic calming measures so frequent removal may be required at certain
times of the year.
 Materials: Materials for all traffic calming measures that will be used in subzero temperatures should be able to withstand repeated freeze-thaw action and
heavy loads at least as well as the surrounding roadway material. Care should be
taken to avoid any materials or paints that may be excessively slippery when wet.
 Signage: Though signs are usually required to inform road traffic of the traffic
calming measure approaching, additional warning signs should be minimized for
aesthetic reasons. It is unnecessary to erect any additional signs; if the traffic
calming measures are navigated at the posted speed there is no risk of vehicle
damage or loss of control (Skene, Pg. 4-2)
 Temporary Installations: Temporary traffic calming installations are often
beneficial to determine an optimal location or specific design of a traffic calming
measure before investing in a permanent fixture. Another advantage of a
temporary installation is to judge community response to the device.
Disadvantages of temporary traffic calming measures are primarily based on poor
aesthetics, creating a public disapproval even for a similar permanent fixture that
may be more pleasing. If a temporary traffic calming measure is aesthetically
pleasing, it may be able to become a permanent fixture (Ewing, pg.82).
 Streetscaping/Landscaping: Adding streetscaping or landscaping to a traffic
calming measure may considerably increase the cost and maintenance but can
improve the measure both aesthetically and functionally. Effective landscaping
on street calming measures can improve community acceptance by softening the
appearance and giving a higher perceived functionality. Streetscaping and
landscaping can also make a road seem narrower therefore reducing speeds.
Specific streetscaping elements can include ornamental items such as lighting,
benches, and planters as well as vegetation. When incorporating streetscaping or
landscaping elements, it is important to maintain good visibility and not sacrifice
street user safety (Skene, 4-2)
To maintain the highest level of safety and appearance, it is essential to
adequately maintain all landscaping measures. There are a few different options
when it comes to maintaining streetscaping and landscaping elements. The city of
Seattle is a good example because of its extensive use of street calming measures.
Seattle initially did all of the landscaping and maintenance for their traffic circles. As
more and more circles were constructed the cost of maintenance became unaffordable
for the city, so a community involvement program was put into place. The city does
the initial landscaping of the measure and the neighbourhood residents are then
responsible for any maintenance or replacement that may be necessary. This method
4
generally worked well for Seattle, but there were some problems with neighbourhood
negligence resulting in a wide range of landscaping quality on the traffic circles.
Other cities such as Portland take full responsibility for construction and maintenance
of their streetscaping and landscaping measures for liability and quality purposes
(Ewing pg.82).
Vertical Deflections
Vertical deflections include raised crosswalks, raised intersections, sidewalk
extensions, speed humps and tables, and textured crosswalks. Vertical deflections are
most effective in reducing traffic speeds rather than traffic volumes.
Raised Crosswalk and Raised Intersection - raised junctions, intersection
humps, plateaus
Raised Crosswalk serving a dual purpose as a speed hump (Delaware Register of Regulations, Pg.
542).
A raised crosswalk can be implemented either mid-street or at an intersection as
long as the boulevard is wide enough to accommodate the required elevation change at
the maximum grade. The height of the raised crosswalk depends largely on desired
vehicle speed (see Design Considerations), but should generally be high enough to
discourage speeding but not produce a risk of vehicle damage or loss of control when
navigated at the intended speed. Speed tables can also serve a dual purpose as raised
crosswalks.
Raised Intersections are flat raised areas covering an entire intersection with
ramps up on all sides (Ewing, pg.34). The flat top is often finished in brick or other
suitable textured material for increased effectiveness and increased aesthetics. Like
raised crosswalks, the height of the intersection depends on desired traffic speed, but
should generally be suitable to reduce speeding while eliminating risk to drivers and their
vehicles. Emergency and transit vehicle volume in the area should also be considered
5
due to the decreased ease of use of large quickly moving vehicles on raised intersections,
especially when turning.
Design Dimensions
The height of raised intersections and raised crosswalks should correspond
throughout the community’s street network in order for citizens to get a better grasp of
the design speeds and operations of the measure. A typical height for an intersection or
crosswalk with a standard 6.67ft ramp would be 3.2in and could change according to the
length of the ramp. The location of a raised crosswalk or intersection in relation to
sidewalks and curbs should be identical to regular crosswalks or intersections. A
minimum 0.6in lip should be maintained at all sidewalk-crosswalk transitions to aid the
visually impaired in acknowledging the presence of the intersection or crossing. The
transition area between the sidewalks and the raised intersection should be lowered to a
0.6in curb face height with a transition slope of no greater than 6%. This transition area
should also have a textured finished such as stamped concrete to provide a physical
indication of the presence of the crossing. Recommendations for these textured surfaces
can be found in the “Geometric Design Guide for Canadian Roads” (GDGCR). The flat
top of the raised intersection should have a minimum grade of 1% to promote drainage.
The dimensions shown have proven to be the best compromise for emergency and transit
vehicle passage, effective speed reduction, and drivability. Raised crosswalks and
intersections should be keyed directly into the existing pavement to provide the most
secure connection
Signing Requirements
A speed hump sign should be located directly beside a raised crosswalk facing
traffic. If a raised crosswalk is located on a one way street, a speed hump sign should be
placed on either side of the street facing traffic. The speed hump sign is necessary for a
raised intersection in the same manner, unless the intersection is stop sign or stop light
controlled in which case no sign is needed. Pedestrian crosswalk signs are necessary on
either side of the raised crosswalk. Solid white reflective pavement markings such as
arrows should also be included directly preceding raised crosswalks and intersections. No
advance warning signs are recommended for either of these traffic calming measures in
order to reduce redundancy and improve aesthetics.
6
(Skene, Pg. 4-4)
*see appendix A for imperial conversions.
7
(Skene, Pg. 4-5)
*see appendix A for imperial conversions.
8
Sidewalk Extension
Concrete sidewalk extension (Regina, SK).
There are two types of sidewalk extensions that can be used depending on
whether the sidewalk and curb are aligned or if the sidewalk is separate from the curb
with a boulevard in-between. In the first case, the sidewalk and curb are directly adjacent
to the roadway so the extended sidewalk can continue across the intersection where a
typical intersection crossing would occur. With a boulevard between the curb and the
walk, the extended sidewalk is offset back from the typical intersection crossing. In both
cases there must be adequate transition area from the regular sidewalk down to the
extended sidewalk.
Design Dimensions
In the case where the sidewalk is joined to the curb, the transition area
approaching the intersection crossing must not exceed a grade of 6% decreasing in
elevation to a recommended height of 0.6in across the intersection. For the separated
curb and walk, the sidewalk is typically lowered in elevation to 1.6in through the
intersection with a 6% grade slope on either side for vehicle passage. Another option in
this case is to construct a raised crosswalk instead of the extended sidewalk. The raised
crosswalk can only be implemented if the distance between the sidewalk and the curb is
at least 5ft or preferably 6.67ft to allow a proper transition slope.
Signing Requirements
Sidewalk extensions always occur at intersections; no additional signs or
pavement markings are required.
9
(Skene, Pg. 4-7)
*see appendix A for imperial conversions.
10
Textured Crosswalk
Textured crosswalks are put into place to further identify the location of a
crosswalk to street users. Although textured crosswalks can be used alone, they are
commonly used to enhance other traffic calming measures such as a raised crosswalk.
The textured surface can be created by concrete stamping, exposed aggregate concrete, or
by the use of a concrete paver. Since textured crosswalks rely on both physical and
visual means to identify their location, added color can increase the effectiveness of the
measure.
Design Dimensions
There are no specific design dimensions for textured crosswalks. The textured
surface should be adequate to provide a visual and physical indication of the crosswalk,
and should not be extreme enough to alter vehicle behaviour over the textured section.
Signing Requirements
No additional signs are required for a textured crosswalk. If pavement markings
are required for another purpose in the textured area, coloured materials may be
necessary for the textured area instead of painting over the textured surface.
Speed Hump - road humps, undulations
(Regina, SK)
Speed humps are the most commonly used traffic calming device in North
America because of their low price, easy construction, and effective results. Typically,
speed humps will reduce vehicle speeds by 5 to 10 mph if placed properly. The Watts
profile hump, a 12 ft parabolic hump between 3 and 4 inches high, with a typical design
speed of 15 to 20mph, is the single most widely used speed control measure in the United
States. Speed humps have four common profiles that have been tested extensively
11
throughout North America: sinusoidal, circular, parabolic, and flat-topped. In some
cases a speed hump can be coupled with a textured surface to increase the effectiveness
of the measure. Any type of speed hump should have the required dimensions to produce
enough driver discomfort to reduce speed to the desired level without sacrificing safety to
street users. A speed hump should be large enough to cause a vertical deflection in the
suspension and body of a vehicle passing over it. A problem with older speed bumps was
the suspension of a vehicle would quickly compress and rebound before any vehicle body
movement took place if taken at speed. Ease of passage for emergency and transit
vehicles must also be considered (Ewing, Pg. 31). Certain measures must also be taken
to allow proper drainage and possibly easier bicycle passage.
Design Dimensions
The type of street in which speed humps are to be placed must be considered for
the proper design dimensions to be used. For residential streets, the most common design
in Canada is a sinusoidal profile 13.33ft long hump with a height of 3.2in (Skene, Pg. 46, 4-9). The Watts profile hump has traditionally been the most widely used hump in the
U.S, but this 4in high design is quickly losing acceptance because of its severe harshness.
Popular new designs being used in the U.S. are a 14 ft hump with the same profile and
height as the Watts, and the 22 ft speed table. Collector streets generally use speed tables
rather than speed humps. Speed tables are similar to speed humps with an extended flat
top (Ewing, Pg.71). The 3.2in height is still used, but the length increases to 23.33ft.
According to the Canadian Guide, the speed table is preferred in this case because of the
higher design speed allowing easier access for emergency and transit vehicles. On either
type of hump, a small drainage culvert should be included close to the curb to promote
drainage. This drainage route can be widened to allow a cyclist to pass through; however
different jurisdictions have varying views on the necessity of this procedure (Skene, Pg.
3-12).
There have been extensive tests conducted throughout North America on different
profiles and dimensions of speed humps, many leading to a shift from speed humps to
speed tables, also referred to as trapezoidal humps or speed platforms. The city of
Portland, Oregon found that the standard 12 ft Watts hump was too abrupt. Instead, they
implemented 14 ft parabolic humps or 22 ft speed tables. The 22 ft or 23.33ft speed
tables were found preferable in many cases especially where there is high traffic volume
and a high concentration of emergency and transit vehicles. The standard speed table
used in the U.S. is 3 to 4 inches high with a 10 ft table-top and 6 ft long ramps on either
side (Ewing, Pg.32). The Canadian version of this is 3.2in in height with 6.67ft long
ramps and a 10ft long table. Some tables are enhanced with brickwork or a textured table
surface for increased aesthetics and effectiveness. Since the 22 ft table is long enough for
the entire wheelbase of a vehicle to be on the flat top at once when crossing it, there is a
less abrupt transition and almost no risk of bottoming out. The table design results in a
higher design speed of 25 to 30mph 1) (Ewing, Pg. 72). Speed tables can also be effective
in serving a dual purpose as a raised crosswalk when placed appropriately. Speed tables
tend to have a significantly higher public approval rating because of their superior
aesthetics and less harsh ride. Although speed tables are a very effective device in many
situations, they have some major drawbacks. Speed tables are expensive compared to a
standard speed hump especially when enhanced with brickwork or a textured surface.
1) 85th percentile speeds
12
Speed humps are also less successful in certain cases in solving a speeding issue because
of their relatively
mild vehicle deflection. The 22 ft table is only one design however, and dimensions can
be varied in order to achieve the desired traffic speed if necessary. In Boulder, CO, for
example, speed tables were designed with heights of up to 6 inches, ramps of 7.5 to 10 ft,
and tables ranging from 18 to 23 ft (Ewing, Pg. 32 – 34).
Speed humps and tables should always be keyed directly into the existing
pavement during construction to provide the most secure connection and minimize
damage to and from snow plow equipment.
Signing Requirements
A speed hump sign should be placed directly beside a hump facing traffic, and if
a speed hump is located on a one-way street, a speed hump sign should be placed on
either side of the speed hump facing traffic. White reflective pavement markings are also
recommended directly preceding the speed hump (Skene, Pg. 4-9).
Horizontal Deflections
Engineering principles state that the more acute the horizontal curvature of a
traffic circle, chicane or curb extension, the greater number of motorists will reduce their
speed. For example, a horizontal curve with a radius of 43ft will normally reduce the
speed of a regular sized vehicle to approximately 15 mph (Ewing, Pg. 68).
Chicane - deviation, serpentines, reversing curves, or twists
(Delaware Register of Regulations, Pg. 16)
Chicane (Delaware Register of Regulations, Pg. 16)
13
A type of horizontal deflection such as a chicane is a curved S-shaped traffic
calming measure which slows the traffic by having a slight curve in road, making
motorists have to sway a little to follow the road. Normally, three alternating curb
extensions are used. (Ewing, Pg. 38). Well-designed chicanes can decrease vehicle
speeds and traffic volume.
Design Dimensions
The purpose of a chicane is to interrupt any single lane of traffic. This is done by
offsetting the middle section of neighbouring chicanes by about 6.67ft. Increasing the
length and reducing the height between chicanes can reduce the strain on emergency and
transportation systems, but can also increase the travelling speed of the traffic. In
addition, a 3.33ft drainage channel is required (Skene, Pg. 4-9, 4-11).
The most important aspect of chicanes is their placement. The location of a
chicane must consider all driveways, fire hydrants, and parking areas. According to
European guidelines, the alignment of chicanes should shift a minimum of one lane
width, and have a deflection of no less than 45 degrees. The purpose of central chicanes
is to inhibit the race track effect (Ewing, Pg. 38).
Two-lane chicanes are most effective on wide residential and collector streets.
Chicanes must have a clear, direct path between them. A chicane on a two-lane street
must have a paved width of 40ft and a chicane on a one-lane street must have a paved
width of 23.33ft.
Chicanes can also be landscaped or streetscaped to enhance the neighbourhood’s
safety and appearance. Landscaping of chicanes has several considerations: sight
distance, cost, climate, and other local regulations. They should also be accepted by the
residents and street users of the area.
Signing Requirements
Normally, Object Markers, Delineation Markers or Bollards with reflective tape
are located in the middle of the chicane to help drivers navigate around the chicanes. For
one way chicanes, a sign should warn motorists that there is a chicane ahead. A Yield
sign as well as a Yield To Oncoming Traffic sign are required in front of two-way one
lane chicane to warn motorists of the narrowing road and the possibly of having to yield.
Stopping Prohibited signs are also required along the chicane (Skene, Pg. 4-9, 4-11)
14
(Skene, Pg. 4-10)
*see appendix A for imperial conversions.
15
Similar Measures
Lateral shifts - axial shifts, staggering or jogs
Curb extensions bend the lanes of the road to create a slight twist which produces
a lateral shift. Lateral shifts are used frequently in Europe as standard calming measures.
Lateral shifts are also used in the United States in cities such as Beaverton and West Palm
Beach. Like chicanes, lateral shifts are a useful and cost-effective way to create extra
parking and slow traffic (Ewing, Pg. 39). Lateral shifts have a travel speed 5 mph more
than a chicane of the same size, making them better suited for main roads (Deleware
Register of Regulations, Pg. 563).
Curb Extension
Extended curb with sidewalk (Regina, SK).
Curb extensions are located at intersections or at mid-block on both sides of the
street to decrease the surface of the roadway. Therefore, they decrease the speed of
vehicles.
Design Dimensions
Usually when approaching a curb extension, each lane should be 10ft wide or if
local policy authorizes, 8.33ft. However, the departing lane must always be 10ft wide.
Mid-block curb extensions require a minimum width of 9.17ft for each lane. Curb
extensions are most useful when they continue past the intersection and in the opposing
direction. A 16.67ft offset is necessary if curb extensions are used diagonally across
from each other at intersection corners.
Curb extensions are 16.67 to 23.33ft in length, except when they act as bus stops.
Curb extensions that are used for bus stops have to be able to hold all buses.
16
Mid-block curb extensions should to also contain room for cross-walks and shifts
in elevation; the minimum requirement is 23.33ft long.
Finally, design considerations should be made for emergency operations, service
vehicles and transit vehicles depending on the communities needs.
Signing Requirements
Object Markers should be used when there is profound snow accumulation, low
visibility of the curb extension and when there is any kind of sharp corner or abrupt curb
extension (Skene, Pg. 4-11).
17
(Skene, Pg. 4-12)
*see appendix A for imperial conversions.
18
Similar Measure
Center island narrowings - mid-block medians, median slow points or median
chokers
To narrow a street, an elevated center island should be located in the middle of the
street to reduce the amount of roadway surface (Ewing, pg.39). Normally, center island
narrowings are about one car length: 6 ft wide and 20 ft long. Center islands are most
effective in reducing travelling speeds when they are closely spaced or they disrupt large
open streets (Delaware Register of Regulations, Pg. 565).
Curb Radius Reduction
Curb Radius Reduction at intersection (Regina, SK).
The name says it all! Curb Radius Reduction is a reduction of the curb radius at
an intersection. Curb radius reduction slows turning motorists and decreases pedestrian
crossing distances.
Design Dimensions
In general, a smaller radius of 10 to 16.67ft is needed for passenger vehicles;
though this can cause problems with large right turning vehicles. They may infringe on
the sidewalk and damage the surrounding area. A hard surfaced material like concrete or
extended sidewalks is alternatives to this problem.
Signing Requirements
No signs are required for curb radius reduction, but signing is required for any
repositioning or replacement of pavement markings or other signs. When combining
curb radius reduction and curb extensions, Object Markers should be used in cases of
profound snow accumulation, low visibility of the curb extension, or where sharp corners
or abrupt curb extensions exist.
19
(Skene, Pg. 4-13)
*see appendix A for imperial conversions.
20
Similar Measures
Neckdown - nubs, bulbouts, knuckles or intersection narrowing
(Delaware Register of Regulations, Pg. 17)
Neckdowns are a type of curb extension which decreases the road surface from
curb to curb at intersections. The main benefit of neckdowns is that by reducing the curb
radius at the corners, the distance a pedestrian must cross is less and the speed of turning
vehicles is decreased. Neckdowns simply help make intersections pedestrian friendly
(Ewing, Pg. 39).
Choker - pinch points, mid-block narrowings, mid-block yield points or constrictions
(Delaware Register of Regulations, Pg. 17)
Chokers are another type of mid-block curb extension which narrows the road
surface by widening the sidewalk area (Ewing, Pg. 41). Two-lane chokers are typically
from curb to curb and have a length of 20 feet (6 meters). Chokers should not block curb
side parking space or driveways. Chokers can be dangerous for cyclists. Bypass lanes
for cyclists should be implemented wherever traffic is heavy (Delaware Register of
Regulations, Pg. 564).
21
On-street Parking
Straight and angle On-street Parking (Regina, SK.)
The location of on-street parking depends on the type and lay out of the street.
On-street parking can occur on both or either side of the street and therefore decreases the
speed of motorists and sometimes traffic volume. One draw back is that on-street
parking requires cyclists to use traffic lanes.
Design Dimensions
The location is the most important aspect of on-street- parking. The location of the
on-street parking must consider driveways, fire hydrants, and parking areas. Note that
on-street parking must not be used to create temporary curb extensions.
Signing Requirements
No parking signs are required to regulate parking in areas of minimum pavement
width and on streets where parking is only permitted on one side. If curb extensions are
combined with on-street parking, signage is required (Skene, Pg. 4-14).
22
(Skene, Pg. 4-15)
*see appendix A for imperial conversions.
23
Raised Median Island
Raised Median Island with landscaping and pedestrian access (Regina, SK).
Lane width needs to be reduced for raised median islands to decrease the travel
speed of motorists on a two lane street. Parking should not be allowed across from a
raised median island. Stopping is also ban at raised median islands. If a mid-block
crosswalk is combined with a raised median island, parking may be permitted if the sight
line is an appropriate distance from the crosswalk. Bicycle lanes can be placed beside
curbs where parking is not permitted.
Design Dimensions
The single lane width next to the median island should not exceed 11.67ft. Any
raised median island should be 10 to 23.33ft long at an intersection or mid-block. The
length should be controlled by the location of the median island to allow access to
driveways and other streets. Raised median islands should have a width of at least 5ft
for required signage, and a pedestrian area. The geometry of island medians must follow
the GDGCR “Geometric Design Guide for Canadian Roads” requirements.
Sign Requirements
A Keep Right sign is needed to guide traffic to the right of the median. A
Stopping Prohibited sign is also required to maintain the necessary pavement widths. For
mid-block crosswalks, Pedestrian Crosswalk signs are compulsory. Pavement markings
should follow GDGCR and MUTCDC guidelines. Object Markers are voluntary (Skene,
Pg 4-14, 4-17).
24
Traffic Circle - intersection islands
A Traffic Circle taking the place of 4-way stop signs (Regina, SK).
Traffic circles allow traffic to flow freely through an indirect path at an
intersection. This causes motorists to slow down and yield before entering the
intersection. Motorists enter the intersection by first turning right and must turn left
around the center island and finally right to exit the intersection (Ewing, Pg. 35).
Landscaping the inner raised section of the island, is a nice and easy ways to improve the
appearance of the intersection. However, the outer portion must be mountable for
medium sized vehicles to maintain functionality (Skene, Pg. 4-17).
There are concerns with traffic circles regarding cyclists and pedestrians. A traffic
circle can take over the intersection leaving cyclists and pedestrians with no where to
cross. The cost is another concern due to the size of a traffic circle and the materials
needed to construct and maintain it (Ewing, Pg. 36).
Mini traffic circles were designed in the 1980’s for more manoeuvrability for
larger vehicles. Mini traffic circles are less expensive than regular ones (Ewing, Pg. 72).
Design Dimensions
A traffic circle must be large enough to create an indirect path for it to be
effective. Although other shapes can be can used, a circle shape is recommended (Skene,
Pg. 4-17). Each traffic circle has specific dimensions according to the size of its
intersection. Traffic circles are sloped from the center of the island for good drainage
(Ewing, Pg.73). For mini traffic circles, one standard single-unit truck is used to
determine its dimensions (Delaware Register of Regulations, Pg. 559).
25
Sign Requirements
Traffic Circle sign is needed to demonstrate the difference in horizontal
alignment. Yield signs are recommended for all entrances of traffic circles (Skene, Pg. 417).
26
(Skene, Pg. 4-18)
*see appendix A for imperial conversions.
27
Similar Measures
Roundabout
Roundabout with appropriate signage (Regina, SK).
Roundabouts slow traffic by directing it counter clock-wise around an island.
However, roundabouts differ from traffic circles because they have a larger radius and
they are more effective on higher volume roadways such as arterial and collector streets.
According to international procedures, roundabouts have a design speed of about 25 mph
(Delaware Register of Regulations Pg. 561). Motorists must yield, and then they must
wait until there is a break in traffic before entering the intersection. Roundabouts assign
rights-of-way to motorists and reduce the use of all-way stop signs (Ewing, Pg. 37-38).
Design Dimensions
Standard roundabouts have inner landscaped areas with a radius of 21ft and outer
mountable areas of 6ft around the inner area. According to the Delaware Register of
Regulations the dimensions of a normal roundabout include: having flaring entry lanes of
11 to 15ft at yield lines. The radii of the roundabout should be smaller than the curved
made by the motorist. The circulating lanes should be between 1 and 1.2 times larger
than the entry lanes. The exit should be larger and straight to let vehicles accelerate as
they leave the roundabout (Delaware Register of Regulations Pg .561).
28
Obstructions:
Traffic calming obstructions are any traffic calming devices that intrude onto a
roadway to reduce traffic volumes and/or traffic speeds. Landscaping or streetscaping is
commonly used to enhance the aesthetics and effectiveness of obstructions. Landscaping
can increase driver awareness of the presence of the obstruction and increase public
approval of the traffic calming measure. Care must be taken not to reduce visibility to
the point of creating a safety hazard when adding landscaping.
Directional Closure - half closure, semi-diverter
A modified exit-only directional closure preventing entrance onto the street and blocking through traffic
(Regina, SK)
A directional closure is formed by the construction of physical barriers blocking
off a particular turning lane at an intersection in order to force traffic to travel on certain
streets and limit the use of others. The two different types of directional closures are
entrance-only and exit-only. The entrance-only closure barricades the right lane of a
residential street at the intersection, allowing vehicles traveling on a collector street to
turn onto a residential street, while blocking the collector street from the residential
street. An exit-only directional closure barricades the left lane of a residential street,
allowing vehicles to turn from a residential street onto a collector street, but limiting
access to the residential street from the collector street (Skene, Pg. 4-17, 4-19).
Design Dimensions
Directional closures must be sufficiently long to discourage traffic from
bypassing the closure by travelling on the wrong side of the street. In Ft. Lauderdale, FL,
a barricade length of 30 ft was found to be sufficient in reducing any illegal bypasses of
the obstruction.(Ewing, Pg.23) Barricades on exit-only closures should have an angle
29
promoting the direction of the desired turn on the side of the barricade away from the
intersection. The exit-only directional closure must also be wide enough so that two
vehicles are unable to pass through the street at the point of the barricade at the same
time, discouraging any through traffic at the intersection. Since directional closures are
most commonly used on two-lane streets, the full single lane closure is generally used.
Gaps on the curb side of the obstruction should be considered to accommodate bicycle
traffic. The bicycle gaps should be 5 to 6.67ft wide, and the adjacent sidewalk curb
should be rolled to reduce the risk to cyclists of clipping their pedals.
Signing Requirements
For an exit-only obstruction, Entry Prohibited and Right or Left Turn Only signs
are required to inform approaching traffic of the obstruction. A sign to exclude cyclists
from these limitations should be included. An Object Marker should also be placed on
the edge of the barrier closest to traffic. On the collector street, One-Way street signs
must be placed in order to inform the traffic on that street that no turning onto the
residential street is permitted. For entry only closures, a Cul-De-Sac sign should be
placed at the beginning of the block containing the closure along with the Entry
Prohibited and Checkerboard warning signs.
30
(Skene, Pg. 4-21)
*see appendix A for imperial conversions.
31
Diverter - diagonal diverters, full diverters, diagonal road closures
(Delaware Register of Regulations, Pg. 13)
Modified diverter, allowing access through from one direction. (Regina, SK)
Diverters are used to eliminate straight through traffic at an intersection by
directing vehicles onto a different street away from the intersection. Diverters are placed
diagonally across an intersection and are almost always incorporated with landscaping in
the area where the previous intersection was located. Pedestrian and cyclist paths should
also be included to allow access to the adjacent street. The paths through the diverter
should have some type of vehicle barricade such as bollards to eliminate illegal use of the
path. To accommodate the need for emergency vehicle access through the diverter, a
lockable or breakaway gate may be used, but in most instances the length of the diverted
route is not long enough to justify this.
Design Dimensions
Diverters should create a turning radius adequate for all vehicles to a maximum
turn radius of 25ft. Parking should be prohibited along a diverter in order to maintain the
32
minimum diverter width of 5ft and to maximize the landscaping area. Bicycle paths and
bollard spacing is most commonly 5ft as well (Skene, Pg. 4-19, 4-23).
Sign Requirements
Single turn signs should be placed preceding the diverter or star diverter, and
parking prohibited signs should be placed along the diverter.
Similar Measures
Star diverters are a star shaped obstruction placed in the middle of a four-way
intersection in a similar manner to a traffic circle. The shape of the diverter forces
vehicles approaching the intersection from any direction to make a right turn. Since the
star diverter does not completely close off the intersection there may be problems with
drivers going around the point of the star and proceeding directly through the intersection
(Ewing, Pg. 23).
33
(Skene, Pg. 4-22)
*see appendix A for imperial conversions.
34
Full Closure - cul-de-sac, dead end
Full closure with streetscaping (Regina, SK)
Full street closures completely eliminate through traffic by blocking the street
with various barriers. Barriers used for full closures include landscaped islands, walls,
gates, and bollards. Closures are discouraged in the vast majority of cities through-out
North America because of the reduced access for emergency vehicles, and the
disturbance that the closures cause to the city’s street networks. Other street calming
measures should always be considered first (Ewing, Pg 19). Access for cyclists and
pedestrians should be included in a full closure barrier.
Design Dimensions
The end of the closed roadway should be altered into a type of cul-de-sac to allow
vehicles to turn around. In order to prevent illegal traffic use, the street closure barrier
should have bollards or other landscaped obstacles placed typically at 5ft intervals.
Pedestrian and bicycle access through the closure should also have a width of 5 to 6.67ft
with adjacent rolled curbs for cyclist safety.
Sign Requirements
A Cul-De-Sac sign should be placed at the entrance to a street with a full closure.
A Checkerboard sign should be placed at the road closure to advise road users that the
street has no exit.
35
(Skene, Pg. 4-24)
*see appendix A for imperial conversions.
36
Intersection Channelization
Channelized intersection using a median island (Regina, SK).
Channelized intersections help prevent certain movements such as through and
left-turn movements in a particular area. The goal of intersection channelization is to
prevent motorists from making illegal turns.
Design Dimensions
The dimensions of a channelized intersection exit vary due to different channel
radii and vehicle size. The right-turn radius of the channel should be large enough to
prevent left turns and through movements. The island channel should be between 66.67
ft2 and 111 ft2 for pedestrian protection.
Sign Requirements
An Entry Prohibited sign is needed on the channel island. Right or left Turn
Only signs are also needed to warn motorist that they are turning into the cross-street. No
Left Turn signs should be placed on the cross-street and the end the channel island.
Other required signs are one Keep Right sign and an Object Marker which should be
placed in the centre of the protected street on the end of the divisional island. An
additional Object Marker must be placed at the pointed corner end.
37
(Skene, Pg. 4-25)
*see appendix A for imperial conversions.
38
Raised Median through an Intersection
(Delaware Register of Regulations, Pg. 13)
Raised median blocking left turn and through access (Regina, SK).
Short medians in the middle of intersections hinder left turn and straight through
movements from residential streets. The median should have sufficient area for
pedestrians and should not be located on streets which require primary emergency aid.
Design Dimensions
The median should be at least 5 ft long and be wide enough to provide a minimum
of 11.67ft lane on each side. It should also extend past the intersection to deter motorists
from driving around the median and turning left. If there is a crosswalk, the median
should be between 16.67 to 23.33ft past the outskirts of the crosswalk, always depending
on driveways and road access.
Sign Requirements
A Keep Right sign and Object Markers should be on each end of the median.
There should be a One-Way sign facing both directions in the middle of the protected
street. No Stopping signs are usually needed depending on lane widths and municipal
policy. Pavement Markings are also required by the MUTCDC (Manual of Uniform
Control Devices for Canada) when nearing the median.
39
(Skene, Pg. 4-27)
*see appendix A for imperial conversions.
40
Right-In/Right-Out Island
Right-In/ Right-out islands are similar to channelized intersections. Their purpose
is to prevent straight through movements and left turns.
Design Dimensions
The Right-In/Right-out islands should be large enough to prevent left-turns and
through movements. The island channel should measure between 66.67 ft2 and 111 ft2 to
protect pedestrians. Depressed curbs and signs should accommodate larger vehicles
which frequent the street often.
Sign Requirements
Two Right-Turns Only signs are needed, one sign in front of the intersection and
the other on the island. A Keep Right sign and an Object Marker are necessary at the end
of the island. An Object Marker is required at the end of the island facing the right
turning lane onto the confined street. An Entry Prohibited sign is necessary on the island
in front of the straight through movement. No Left Turn signs should be placed on the
far cross-street as well as at the end of the channel island. Right or Left Turn Only signs
are needed; the signs should warn motorist that they are turning into the cross-street. All
sign regulations should correspond to MUTCDC standards.
41
(Skene, Pg. 4-28)
*see appendix A for imperial conversions.
42
Traffic Calming Signs
Some commonly used traffic calming signs (Delaware Register of Regulations, Pg. 46)
Most of the signs are traditional MUTCDC signs with the exception of the Speed Hump
sign and the Traffic Calmed Neighbourhood sign.
Speed Hump Sign
This original speed hump sign should be located prior to the speed hump with the
educational tab sign.
43
Traffic-Calmed Neighbourhood sign
The traffic-calmed neighbourhood sign as well as the supplementary tab sign are
now required in all traffic-calmed neighbourhoods (Skene, Pg. 4-23, 4-26, 4-29).
44
Appendix A
Conversion Table :
Length
Velocity
1 m = 3.33 ft
1 cm = 0.40 in
1 mm = 0.04 in
1 kph = 0.625 mph
Abbreviations:
Length
Velocity
Acceleration
ft = feet
in = inch
km = kilometer
m = meter
cm = centimeter
mm = millimeter
mph = miles per hour
kph = kilometres per hour
g = acceleration due to gravity
45
Glossary
Channelization
Directed motion of vehicles and/or pedestrians at an intersection
through the use of raised median islands and signs.
Chicane
A curved S-shaped traffic calming measure which slows the traffic
by having a slight curve in road, making motorists have to sway to
follow the road. Normally, three alternating curb extensions are
used to create a chicane.
Collector Street
A street where vehicles have free movement and access.
Curve
Horizontal deflection creates a change in direction making motorists
turn their vehicles. Vertical deflection creates a change in gradient
making motorists ascend the elevated area.
Deflection
A physical change in the vertical or horizontal characteristics of the
road.
Depressed Curb
A concrete curb which has a lowered section to help drainage or
pedestrians. It can also be called a drop curb.
Divert
Redirect traffic by utilizing physical barriers and/or signs.
GDGCR
“Geometric Design Guide for Canadian Roads”
Local Street
Residential Street
Measure
A traffic regulating device which controls the movement of motorists,
cyclists, and pedestrians.
MUTCDC
“Manual of Uniform Traffic Control Devices for Canada”: Gives a
consistent procedure for proper signage and pavement marking for
traffic control devices.
Regulation
A policy supported by government.
Rolled Curb
A sloped concrete curb.
Sidewalk
Extension
The continuation of a sidewalk across an intersection. May be raised
or unraised.
Standard
Common specifications for traffic calming devices found to be
suitable under normal circumstances
46
Streetscaping
Physically beautifying the area surrounding a traffic calming measure
while aiding the measure itself. Some examples include planters,
benches, and waste receptacles.
Traffic Calming Physical devices that modify motorist behaviour in order to decrease
traffic speed, traffic volume, or both. Traffic calming enhances the
safety of other street users.
Traffic Volume The amount of traffic that travels on a certain roadway in a specific
time frame.
47
Bibliography
Ewing, Reid. (1999) Traffic Calming: State of the Practice. Institute of Transportation
Engineers. Ch. 1 – 4
Skene, Michael, Project Chair. (1998). Canadian Guide to Neighbourhood Traffic
Calming. Transportation Association of Canada. Pg. 3-12, 4-10 – 4-30
Delaware Register of Regulations. ( 2000). Final Regulations: Geometric Design of
Traffic Calming Measures. Vol. 4, issue 3. Pg. 561-565
48