SR-506-003-05 (2)
Attachment A
City of Santa Monica
Residential Traffic Management Handbook
City of Santa Monica
Transportation Management Division
1685 Main Street, Room 115
Santa Monica, California 90401
310-458-8291
Revised February 2000
Table of Contents
Introduction
To Be Determined
Process and Procedures
"
Measures that may impact speed
Stop signs "
Speed limit "
Radar trailer "
Traffic circle "
Left-turn lane "
Two-way left-turn lane "
Median island "
Intersection median island "
Curb extension "
Measures that may limit access
No left turn, no right turn, do not enter "
One-way "
Measures that may have limited application
Semi-diverters (one-way) "
Cul-de-sac "
Measures not recommended for use
Diagonal diverter "
Diverters/Forced turn channelization "
Rumble strip "
Miscellaneous non-standard devices "
Revised February 2000
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Introduction
This publication is offered to assist residents in addressing some of their local traffic
concerns. It contains information about different traffic control measures and roadway
design features that are available, and lists the advantages and disadvantages of each.
Generally, residents can contact the City of Santa Monica Transportation Management
Division to request the installation of these traffic measures.
Upon request, City staff will conduct an initial assessment of a street or neighborhood,
including a review of accident history, speed and volume data. This assessment can
be done in approximately 90 days. Following the initial assessment, staff can provide
information on measures that could be considered for a particular location pursuant to
the policies in this handbook. Implementation of measures that have minimal negative
impact and low cost can be done right away. Implementation of others may require
residents to show support through a petition process. Implementation schedules will
depend on funding availability.
For information, this handbook describes some traffic control measures that are not
recommended for use on City streets. The City has considered these devices and
found they were not appropriate because they may cause or create more problems
than they resolve.
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Process and Procedures
In general, the process and procedures for residents to obtain consideration for any of
the traffic control measures is quite simple. A resident or residents should send a
written request to the Transportation Management Division of the City of Santa Monica
at the address shown on the front cover. Upon receipt of the letter, the request will be
assigned to an engineer who will conduct an initial assessment. This assessment may
include the collection of traffic data such as traffic volumes, speed surveys, field
measurements and observations, and should be completed in approximately 90 days.
A determination will be made and the requestor(s) will be advised of the results.
Implementation of measures that have minimal negative impact and low cost can be
done right away. Measures such as the construction of traffic circles will require
consultation with all neighborhood residents and may involve petitioning, balloting and
neighborhood meetings. If the measures under consideration are likely to affect
multiple street segments, the City will coordinate a process with all potentially affected
neighborhood residents.
Minimum Criteria
Measures such as traffic circles may be installed only on streets that
meet the following criteria:
1. The street is classified as a local or collector street by the General Plan
Circulation Element and residential uses predominate its frontage.
2. The speed limit is 25 miles per hour unless City Council has adopted an
ordinance establishing the speed limit at 30 miles per hour.
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3. The measured average speed exceeds thirty-two miles per hour.
4. The roadway is no wider than 40 feet, and has no more than two lanes of traffic,
one in each direction.
5. The grade of the roadway is five percent or less within 200 feet (for speed
humps only).
7. There are no stop signs or traffic signals controlling traffic on the street within
150 feet of the proposed installation.
8. The installation will not shift or divert traffic to other adjacent streets.
9. The installation will not significantly increase emergency response times to any
neighboring area.
10. Residents living in 60% of the adjacent dwelling units have been informed of the
measure under consideration including its potential to reduce emergency
response time and have provided written support for the measure through a
ballot or petition.
Priority
Requests shall be prioritized on the basis of:
1. Accident history
2. Measured speed
3. Traffic volume
4. Date of request
5. Location (proximity to school, park or other pedestrian generator)
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Measures That May Impact Speed
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Stop Sign
Description:
"STOP" sign
Effect on speed:
Effect limited to within approximately 200 feet of the stop
sign. Consistently shown to have little effect on the speed
of traffic in mid-block locations.
Effect on volume:
Little effects if the bypassed route is congested or delayed.
May have some effect if use of a short cut is marginal.
Other positive aspects:
Speeds are reduced at intersections where pedestrian
activity is expected.
Other negative aspects:
Increased noise near stop sign controlled intersection,
especially where buses and trucks are part of the traffic mix.
Corresponding to this is an increase in air pollution
emissions.
Discussions:
Stop signs do reduce vehicle conflicts, but their misuse may
cause reduced safety by inducing rolling stops or non-
compliance at a specific unwarranted location, and by
increasing general disrespect for the stop sign at all
locations. Both of these aspects are difficult to measure
quantitatively.
Primary criteria:
Some of the key factors to determine whether stop signs
should be installed include traffic volumes, accident history,
field conditions, proximity to schools and use as a route to
school.
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Speed Limit Sign
Description:
Speed limit sign
Effect on speed:
Signing generally has a negligible impact on actual
operating speeds. The majority of people drive at a speed
that they consider reasonable and prudent for the prevailing
conditions.
Effect on volume:
None
Other positive aspects:
None
Other negative aspects:
In theory, if speed limit is established at or near the level of
current operational practice, it is not addressing "the
problem," as perceived by residents. If a speed limit is set
at an artificially low level, it may build unrealistic
expectations on the part of residents, and may not be
enforceable.
Discussion:
The California Vehicle Code (State Law) sets a 25 mph
?prima facie? speed limit automatically for all residential
streets. Signing is not required for enforcement of the prima
facie speed limit to occur and hold up in court. In some
situations, signing is advisable to notify motorists of a
change of speed limit across an intersection, and such may
occur on the local residential street system. Negligible
impact on speeds suggests that overuse may be
counterproductive. A few well placed signs are more likely
to be noticed and heeded than a proliferation of randomly
placed ones.
Primary criteria:
A key factor for the installation of a speed limit sign is the
determination that it is advisable to notify or remind
motorists of the speed limit.
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Radar Trailer
Description:
Portable radar speed meter capable of measuring vehicle
speed and graphically displaying the speed of the motorist.
Effect on speed:
Effect limited to within sight distance of radar trailer. In
general, no lasting effect or impacts on actual operating
speeds of repeat users. May help increase motorist
awareness of posted speeds.
Effect on volume:
None
Other positive aspects:
Speeds may be reduced during short intervals where the
radar trailer is located. An effective public relations and
educational tool.
Other negative aspects:
Not an enforcement tool. Not effective on multi-lane
roadways with significant traffic volumes due to limited
ability to differentiate between multiple approaching
vehicles.
Discussions:
Radar trailers are most useful in public awareness and
education and for maintaining a high profile on local
roadways. In general, it is not effective in modifying long-
term habits or modifying a driver's perception of safe,
reasonable speeds. In order to obtain results, selective
enforcement should take place after the trailer is removed.
The enforcement, though short term, will curtail speed
violations for a period of time.
Primary criteria:
Some of the key factors to determine where the trailer
should be used include the speed of existing traffic and the
availability of the radar trailer.
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Traffic Circle
Description:
A small circular island, usually landscaped, placed in the
center of an existing local street intersection or at mid-block
locations between adjacent intersections creating a small
"roundabout" or "rotary".
Discussion:
These devices provide aesthetic appeal as well as speed
reduction. They can help differentiate between residential
and commercial areas. At intersections, they may provide
improved safety, compared to stop signs.
Effect on speed:
Locations in the City of Santa Monica have shown that
speeds have been reduced. Overall route effectiveness
varies with circle spacing.
Effect on volume:
For residential streets, no traffic diversion is expected.
Diversion is not the purpose of traffic circles. Their purpose
is to address speed.
Negative effects:
The installation of traffic circles can in the loss of six to eight
on-street parking spaces at each circle. The vehicle path
around a traffic circle results in vehicles driving immediately
adjacent to the curb and parkway. Traffic circles, like stop
signs and speed humps, may result in a pattern of
braking/accelerating, braking/accelerating driver behavior.
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Primary criteria:
Excessive speeding on a local or collector street.
(Diagram of Speed ?Hump? vs Speed ?Bump?)
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Left-Turn Lane
Description:
A designated traffic lane at intersections or driveways
providing exclusively for left-turns and u-turns.
Effect on speed:
May tend to increase speeds due to reduced numbers of
vehicles stopping in the through lanes to complete left turns
and a degree of separation provided between vehicles
traveling in opposite directions. However, can also reduce
speeds if through lanes are eliminated or substantially
reduced in width.
Effect on volume:
Volume impacts could range from increases to decreases
depending on the specific circumstances of the installation.
When combined with parking reductions and no lane
reductions, volumes will likely increase. Lane width and
lane reductions could result in reduced volumes.
Other positive aspects:
Less impact on through traffic. Reduction in potential for
rear end accidents. If applied to large residential streets,
through traffic may feel more confined by parking and lane
lines, potentially reducing travel speeds, capacity and
possibly volumes.
Other negative aspects:
May divert traffic to other streets if through lanes are
eliminated. May give motorists a more protected or isolated
feel when traveling in through lanes potentially reducing the
perception of a residential neighborhood. Typically requires
elimination of on-street parking within turn lane area.
Discussion:
Left-turn lanes are often used on roadways to provide
convenient and safe access to driveways. Applications in
residential environments are not common. Installations may
help to increase capacity at signalized or multi-way stop
controlled intersections.
Primary criteria:
Some of the key factors to determine if a left-turn lane
should be installed include existing traffic volumes and
intersection turning movements, roadway width, accident
history and parking or lane reductions.
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Two-Way Left-Turn Lane
Description:
Two sets of solid yellow and broken yellow lines separated
by a minimum of 9 to 10 feet between traffic lanes in
opposing directions, to provide a continuous lane for left
turns in both directions.
Effect on speed:
May tend to increase speeds due to reduced numbers of
vehicles stopping in the through lanes to complete left turns
and a degree of separation provided between vehicles
traveling in opposite directions. However, can also reduce
speeds if through lanes are eliminated or substantially
reduced width.
Effect on volume:
Volume impacts could range from increases to decreases
depending on the specific circumstances of the installation.
When combined with parking reductions and no lane
reductions, volumes will likely increase. Lane width and
lane reductions could result in reduced volumes.
Other positive aspects:
Less impact on through traffic. Reduction in potential for
rear end accidents. If applied to large residential streets,
through traffic may feel more confined by parking and lane
lines potentially reducing travel speeds, capacity and
possibly volumes. More convenient access to multiple
driveway.
Other negative aspects:
May divert traffic to other streets. May give motorists a more
protected or isolated feel when traveling in through lanes
potentially reducing the perception of a residential
neighborhood.
Discussion:
Two-way left-turn lanes are often used on arterial roadways,
especially in commercial areas to provide convenient, safe
and flexible access to multiple driveways. Applications in
residential environments are not common, but may be
appropriate under certain circumstances. Results of
providing two-way left-turn lanes to reduce roadway width or
eliminate through lanes will vary significantly depending on
the location. Potential installations should be evaluated
very carefully.
Primary criteria:
Similar to left-turn lanes.
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Median Island
Description:
A physical barrier typically found on major streets which can
effectively eliminate left turns onto cross streets, and which
can also eliminate local street straight through cross traffic.
Effect on speed:
May tend to discourage a speed-prone element of the
driving population from the local street. Left-turns onto local
streets should also be reduced, thereby enhancing flow
characteristics, including speed, on the major or non-local
street.
Effect on volume:
Will reduce local street volume to the extent that the moves
eliminated contributed to that volume.
Other positive aspects:
Less impact on the major or non-local street as it helps its
efficiency, which in turn makes intrusion into neighborhoods
less attractive. The resulting right-turn-in, right-turn-out
operation should also be an enhancement to safety.
Other negative aspects:
May overload other locations where left-turn opportunities
continue to exist. This could negatively affect both safety
and efficiency of the major or non-local street. This
treatment will also inconvenience local residents who will be
forced to drive longer more circuitous paths to reach their
homes.
Discussion:
Median islands are a well established mechanism. Care
must be taken along the non-local street that safety and
congestion problems are not created elsewhere, and that
drivers are not encouraged to use private property (parking
lots, etc.) to assist in turning around or otherwise
circumventing the intent of the barrier. A median barrier can
take many forms, including a closely spaced row of flexible
delineator posts, a series of pre-cast curb sections affixed to
the pavement, or an asphalt or concrete curbed island with
or without decorative landscaping and surface treatment.
Costs vary widely among the options.
Primary criteria:
Some of the key factors to determine if a median island
should be installed include support by local residents,
impact on access, impact at intersections where left turns
are still allowed, roadway width and cost.
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Intersection Median Island
Description:
A narrow, painted median island on apporoaches to local
street intersections.
Effect on speed:
Slight slowing may result.
Effect on volume:
Insignificant, unless the number of lanes is reduced (which
is not likely to be the case on a residential street).
Other positive aspects:
None
Other negative aspects:
May result in loss of curbside parking.
Discussion:
The psychological effect of median islands may be their
most important attribute.
Primary criteria:
Some of the key factors to determine if intersection median
islands are appropriate include roadway width (minimum 10
to 11-foot travel lanes are required with a minimum two-foot
wide median) and impact on parking.
Effect on speed:
May tend to discourage a speed-prone element of the
driving population from the local street. Left-turns onto local
streets should also be reduced, thereby enhancing flow
characteristics on the major or non-local street.
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Curb Extension
Description:
Narrowing of a street at an intersection or mid-block location
in order to reduce the roadway width by construction of a
sidewalk widening ("curb bulb? or ?extension").
Effect on speed:
Slight slowing is normally the result.
Effect on volume:
Insignificant, unless the number of lanes is reduced (which
is not likely on a residential street).
Other positive aspects:
Shorter pedestrian crossing distances and better motorist-
pedestrian cross visibility. Creates added streetscape area
for pedestrian activities or landscaping. Provides an
opportunity for gateway treatment to define a neighborhood.
Allows signs to be placed closer to driver's line of vision.
Other negative aspects:
Potential collision obstacle for motorists. May impede
bicycle mobility and safety. May result in loss of curbside
parking. Can impede legitimate truck movements (fire
apparatus, refuse vehicles). May require reworking of street
drainage, which can be difficult and costly.
Discussion:
The psychological effect of curb extensions may be their
most important attribute. Used on several streets in an
area, they may serve to define the outer limits of a
neighborhood, particularly if a unified design concept is
employed.
Primary criteria:
Some of the key factors to determine if curb extensions are
appropriate include roadway width (minimum 10 to 11-foot
travel lanes are required), impact on parking, impact on
turning movements, and impact on City services such as
street cleaning and waste collection.
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Measures That May Limit Access
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No Left Turn, No Right Turn, Do Not Enter
Description:
Turning prohibitions or restrictions may be accompanied by
a sign panel indicating specific days and or hours of
applicability. A combination of these signs may appear at a
location, depending on which movement(s) is (are) intended
for exclusion.
Effect on speed:
May tend to exclude a speed-prone element of the driving
population, otherwise no effect. In the case of turn
prohibitions, the speed on the main street may increase
slightly as a result of reduced intersection conflicts.
Effect on volume:
Significant, though not total, exclusion of indicated
movements may have a significant positive impact on total
volume.
Other positive aspects:
In the case of turn prohibitions, safety may increase on
origin street (often a major or non-local). Does not impede
emergency vehicles, as they can readily violate the
restriction.
Other negative aspects:
Prohibition is subject to some deliberate violation,
particularly at low volume local-local intersections within the
neighborhood where police presence is infrequent. Safety
may decrease at other locations if drivers are forced to
make hazardous movements to compensate for restricted
movements.
Discussion:
Can be effective, but placement and use needs to be
carefully analyzed so that desirable and necessary moves
are not unduly restricted. Area residents need to
understand that turn restrictions apply to them as well as to
outsiders.
Primary criteria:
Some of the key factors to determine if turn prohibitions are
applicable include available adjacent arterial streets, impact
on adjacent residential streets, support of residents and
impact on adjacent intersections where turns conyinue to be
allowed.
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One-Way
Description:
Signing to designate streets or segments of streets as "one
way" (sometimes in a maze pattern) to deliberately deter
through movements.
Effect on speed:
One-way operation may encourage increased speeds,
although intentional discontinuities may mitigate this effect
somewhat.
Effect on volume:
May reduce total volume on subject street, but care must be
taken not to shift diverted traffic to another nearby local
street.
Other positive aspects:
Allows wrong way entry by emergency vehicles. Safety is
inherently greater on one-way segments, but care must be
taken to handle end treatments properly.
Other negative aspects:
Adverse travel distance may result for local residents.
Restriction is subject to intentional violation. Too many
intentional discontinuities can confuse service vehicles and
residents.
Discussion:
Can be effective, but placement and use needs to be
carefully analyzed so that desirable or necessary moves are
not unduly restricted. Area residents need to understand
that one way restriction applies to them as well as
"outsiders".
Primary criteria:
Some of the key factors to determine if one way streets are
appropriate include roadway width, impact on adjacent
streets, impact on areawide traffic patterns and support of
residents.
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Measures That May Have Limited Application
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Semi-Diverter
Description:
A physical barrier across half a street, usually at an
intersection, which precludes movement in one direction but
not the other.
Cul-De-Sac
Description:
Complete closure of a street either at an intersection, or at a
midblock location.
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Measures Not Recommended For Use
This information is being provided to answer questions that may be asked about these
devices. Although these measures are not recommended for use on City of Santa
Monica streets, this information is provided to document that they were considered and
evaluated and found to be inappropriate.
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Diagonal Diverter
Description:
Barrier between diagonally opposite corners of a four-
legged intersection, thus creating two unconnected L-
shaped intersections.
Diverters/Forced-Turn Channelization
Description:
A traffic island specifically designed to force certain traffic
move(s) and prohibit other(s).
Discussion:
The above mentioned devices are not recommended for use
on City of Santa Monica streets. These devices shift traffic
volumes and other related traffic conditions to adjacent
residential streets, and therefore, do not address the
problems, but simple shift the problems to others. This is
not an acceptable result of implementing residential traffic
management techniques.
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Rumble Strip
Description:
Rough or patterned section of pavement, created by asphalt
strips or raised ceramic pavement markers for the purpose
of alerting drivers of a specific control device (e.g.
unexpected stop sign) or a particularly unique condition
(e.g. sharp curve).
Discussion:
This device is not recommended for use on City of Santa
Monica streets since it is not a viable residential
neighborhood treatment due to the noise and vibration
created.
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Miscellaneous Non-Standard Devices
Description:
?Slow?, ?Children at Play? or odd-value speed advisory
signs.
Discussion:
These devices are not recommended because these
measures produce no lasting effect and they are not
recognized as official traffic control devices. The novelty
effect wears off quickly and they no longer command the
attention of repeat users of the street. In addition, lack of
legal meaning or established guidelines for use can lead to
agency exposure to liability. A ?Slow? sign by itself is too
ambiguous to have any effect, and, for that reason, is not
approved for use as a primary message. The often
requested ?children at play? sign has the potential of being
misinterpreted by residents who may see it as official
approval of street playing, and may therefore lead to liability
exposure.
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