Appendix C. TRAFFIC CALMING MEASURES

Vertical Deflection

Measure	Definition/Application	Advantages	Disadvantages	Special Considerations
	Paved hump in the street that causes discomfort at high speeds.	• Effective if used in series at 300 to 500 foot spacing. • Self-enforcing. • Relatively inexpensive.	• If not properly designed, drivers may skirt around to reduce impact. • Drivers may speed up between humps. • May increase volumes on other streets. • Difficult to properly construct.	• Emergency vehicles • Drainage • Signage • Snow removal Estimated Cost Range = $1,000.00 to $2,000.00
	• Speed reduction • Possible traffic reduction
	Speed hump designed as a pedestrian crossing.	• Highlights crosswalk. • Excellent pedestrian safe treatment. • Aesthetically pleasing if designed. • Relatively inexpensive.	• Drivers may speed up between humps. • May increase volumes on other streets. • Difficult to properly construct.	• Emergency vehicles • Drainage • Signage • Snow removal Estimated Cost Range = $1,000.00 to $2,000.00
	• Speed reduction at crossing • Possible traffic reduction
	Patterned sections of rough pavement.	• Relatively inexpensive to install. • Create driver awareness.	• High maintenance. • May adversely impact bicyclists. • Noisy by design, and not recommended for all areas.	• Emergency vehicles Estimated Cost Range = $1,000.00 to $2,000.00
	• Possible speed reduction
	Dips in the street that can be used to carry run-off as well as cause discomfort to drivers at high speeds.	• Effective if used in series at 300 to 500 foot spacing. • Self-enforcing. • Relatively inexpensive during initial construction.	• Drivers may speed up between dips. • May increase volumes on other streets. • Not usually appropriate for existing streets with established drainage patterns.	• Emergency vehicles • Drainage • Signage Estimated Cost Range = $1,000 to $2,000
	• Speed reduction • Possible traffic reduction
	Raised plateau where streets intersect.	• Slows vehicles in the most critical area, reducing conflict. • Highlights intersection. • Excellent pedestrian safety treatment. • Aesthetically pleasing if well designed. • Better for emergency vehicles than speed humps.	• Increases difficulty of making a turn. • Increased maintenance. • Requires adequate signage and driver education.	• Emergency vehicles • Drainage • Signage • Snow removal Estimated Cost Range = $4,000.00 to $6,000.00
	• Speed reduction • Possible traffic reduction
Horizontal Deflection
	Entry treatment that communicates a sense of neighborhood identity and a change in traffic conditions.	• Positive indication of a change in environment from arterial road to residential street. • Reduces pedestrian crossing distances. • On wide streets, provides space for landscaping in the median.	• Low speed of turning vehicles may restrict flow on adjacent arterial.	• Emergency vehicle access • Lighting • Irrigation and maintenance of landscaping Estimated Cost Range = $5,000.00 to $25,000.00
	• Speed reduction at entry • Traffic reduction
	Mid-block expansion of landscaped areas and/or on-street parking in order to physically narrow the street to a single traffic lane.	• Minor inconvenience to drivers. • Minimal inconvenience to local traffic. • Shorter crossing distance for pedestrians. • Provides space for landscaping. • Effective when used in series.	• Unfriendly to bicyclists unless designed to accommodate them. • Conflict between opposing drivers arriving simultaneously could create problems. • Contrary to driver expectation of unobstructed flow.	• Emergency vehicle access • Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $8,000.00 to $20,000.00
	• Speed Reduction • Traffic Reduction
	Mid-block expansion of landscaped areas and/or on-street parking in order to physically narrow the street.	• Minor inconvenience to drivers. • Regulates parking if bulb-outs are placed in no parking zones. • Protects parked vehicles. • Reduces pedestrian crossing distance. • Provides space for landscaping.	• Less effective in reducing speed and diverting traffic than the single-lane application. • Unfriendly to bicyclists unless designed to accommodate them.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $8,000.00 to $20,000.00
	• Speed reduction • Possible traffic reduction
	Offset curb extensions used to narrow the street to a single lane and create angled deviations in the path of travel.	• Minor inconvenience to drivers. • Minimal inconvenience to local traffic. • Shorter crossing distance for pedestrians. • Provides space for landscaping. • Effective when used in series.	• Unfriendly to bicyclists unless designed to accommodate them. • Conflict between opposing drivers arriving simultaneously could create problems. • Contrary to driver expectation of unobstructed flow.	• Emergency vehicle access • Lighting • Signage • hg;Irrigation and maintenance of landscaping Estimated Cost Range = $8,000.00 to $20,000.00
	• Speed reduction • Traffic reduction
	Offset curb extensions used to narrow the street and create angled deviations in the path of travel.	• Same as Single-Lane Angled Slow Point, except pedestrian safety is reduced.	• Same as Single-Lane Angled Slow Point, except less effective in controlling speeds because drivers can create a straighter through movement by driving over centerline.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $8,000.00 to $20,000.00
	• Speed reduction • Possible traffic reduction
Horizontal Deflection
	Island or barrier in the center of a street that narrows lanes and segregates traffic.	• Provides a refuge for pedestrians and bicyclists. • Can improve the streetscape if landscaped.	• Limited reduction in vehicle speeds.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $5,000.00 to $10,000.00
	• Possible speed reduction • Possible traffic reduction
	Modification of "T" intersection layout which gives priority to turning traffic.	• Reduces through traffic along the top of the "T". • May provide space for landscaping.	• Can cause confusion regarding priority movements, which may lead to accidents.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $5,000.00 to $10,000.00
	• Speed reduction • Possible traffic reduction
	Physical curb reduction of road width at an intersection.	• Reduces pedestrian crossing distance. • Can be used in multiple applications or on a single segment of roadway. • Aesthetically pleasing if landscaped.	• Unfriendly to bicyclists unless designed to accommodate them. • Landscaping may cause sight line problems.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $20,000.00 to $30,000.00
	• Speed reduction
	Offset curb extensions that cause deviation in the path of travel.	• Imposes minimal inconvenience on local traffic. • Reduces pedestrian crossing distance. • Provides large area for landscaping. • Reduces speed without significantly increasing emergency response time. • Aesthetically pleasing.	• May create opportunities for head-on conflicts on narrow streets. • Cost is greater than many other devices. • Unfriendly to bicyclists unless designed to accommodate them.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $20,000.00 to $30,000.00
	• Speed reduction • Possible traffic reduction
	Narrow winding driveway section placed between two standard street segments.	• Changes the initial impression of the street. Appears to be a road closure yet allows through movements for local traffic. • Provides a large area for landscaping.	• High cost can be prohibitive. Best installed in conjunction with street reconstruction or initial construction. • Unfriendly to bicyclists unless designed to accommodate them.	• Emergency vehicle access • Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $20,000.00 to $50,000.00
	• Speed reduction • Traffic reduction
	Raised circular area placed in the center of an intersection. Drivers travel in a counter-clockwise direction and are required to yield upon entry.	• Reduces accidents by 50% to 90% over stop control. • Provides space for landscaping. • Cheaper to maintain than signals. • Effective at multi-leg intersections. • Provides equal access to intersections for all drivers. • Provides a good environment for bicyclists.	• May be restrictive for larger vehicles if designed to a low speed. (This can be minimized by the use of a mountable apron.) • Right-of-way may need to be purchased to accommodate left turns by large vehicles. • Initial safety issues as drivers adjust. • May increase volumes on adjacent streets.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $10,000.00 to $50,000.00
	• Speed reduction at intersection • Possible traffic reduction
	A block with narrow entry points and high-density parking which functions similarly to a parking lot.	• Provides a low speed shared environment that is safe for all users. • Improves amenity without restricting access. • Provides flexibility for on-street parking.	• High cost unless part of original design. • May result in an increased number of low speed accidents.	• Emergency vehicle access • Signage Estimated Cost Range = $15,000.00 to $25,000.00
	• Speed reduction • Traffic reduction
Obstruction
	Small traffic islands installed at intersections to restrict and channelize turning movements.	• Changes driving patterns • May reduce cut through traffic. • May be attractive if landscaped.	• May increase trip length for some drivers. • May increase response times for emergency vehicles.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $4,000.00 to $8,000.00
	• Traffic reduction • Possible speed reduction
	Barrier placed diagonally across a four-legged intersection, interrupting traffic flow across the intersection.	• Eliminates through traffic • Provides area for landscaping. • Reduces traffic conflict points. • Increases pedestrian safety • Can include bicycle path connection.	• May inconvenience residents gaining access to their properties. • May inhibit access by emergency vehicles. • May divert through traffic to other local streets. • Altered traffic patterns may increase trip length.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $10,000.00 to $20,000.00
	• Traffic reduction • Speed reduction
	Blockage of one direction of traffic on a two-way street. The open lane of traffic is signed one-way, and traffic from the blocked lane is not allowed to drive around the barrier in the open lane.	• Reduces through traffic in one direction. • Allows two-way traffic on the remainder of the street. • Shorter crossing distance for pedestrians. • Provides space for landscaping. • Two-way bicycle access can be maintained. • Emergency vehicles can drive around partial closure with care.	• Reduces access for residents. • Compliance with semi-diverters is not 100%. • May increase trip length.	• Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $10,000.00 to $20,000.00 each side of intersection
	• Traffic reduction • Speed reduction
	Street closed to motor vehicles at the end of a block using planters, bollards, barriers, etc.	• Eliminates through traffic. • Improves safety for all street users. • Pedestrian and bicycle access maintained.	• Reduces emergency vehicle access. • Reduces access to properties for residents. • May increase trip lengths. • May increase volumes on other streets.	• Emergency vehicle access • Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $15,000.00 to $25,000.00
	• Traffic reduction • Speed reduction
	Street closed to motor vehicles mid-block using planters, bollards, barriers, etc.	• Eliminates through traffic. • Improves safety for all street users. • Pedestrian and bicycle access maintained.	• Reduces emergency vehicle access. • Reduces access to properties for residents. • May increase trip lengths. • May increase volumes on other streets.	• Emergency vehicle access • Lighting • Signage • Irrigation and maintenance of landscaping Estimated Cost Range = $15,000.00 to $25,000.00
	• Traffic reduction • Speed reduction
	Street upon which motor vehicles may operate in just one direction.	• Increased safety due to lack of opposing traffic. • Can be used to open up more resident parking. • Maintains reasonable access for emergency vehicles. • Can discourage through traffic.	• Can lead to increased vehicle speeds. • May increase trip lengths. • May increase volumes on other streets. • Initial safety concerns as drivers adjust. • Alternative route must exist.	• Signage Estimated Cost Range = $2,000.00 to $3,000.00
	• Possible traffic reduction
	Intersection at which opposing legs carry one-way traffic in different directions.	• Increased safety due to lack of opposing traffic. • Maintains reasonable access for emergency vehicles. • Interrupts the flow of through traffic.	• May increase trip lengths. • May increase volumes on other streets. • Initial safety concerns as drivers adjust. • Alternative route must exist.	• Signage Estimated Cost Range = $3,000.00 to $5,000.00
	• Traffic reduction