Traffic Calming

Common traffic calming measures

• Speed humps

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  A speed hump is a raised area of a roadway, which causes the vertical upward movement of a traversing vehicle. Speed humps are one of the most widely used and cost-effective types of traffic calming.

  Advantages:

  • Reduce overall speeds
  • Cost efficiency allows for incorporation into most projects
  • No effects on bicycles riding at moderate speeds
  • No effect on resident access, street sweeping, and on-street parking
     

  Disadvantages:

  • Emergency services can be delayed up to 15 seconds
  • Have negative effects on transit route travel times
  • Increased travel noise levels
  • Negative effects on snow plowing/removal; plow operators must slow and manage blade carefully to avoid damaging the humps
  • Traffic may be diverted to parallel streets without traffic calming measures 
     

  Cost: low – medium

• Curb extensions

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  A curb extension (also known as curb bulb or bulb-out) is a horizontal intrusion of the curb into the roadway resulting in a narrow section of the roadway.

  Advantages:

  • Reduces vehicle speeds by increasing drivers’ feeling on “confinement”
  • Reduce pedestrian crossing distance at intersection that may reduce pedestrian-vehicle conflicts
  • No effects on resident access, snow plowing, and street sweeping
     

  Disadvantages:

  • Potential loss of on-street parking
  • Cyclists can feel squeezed closer to vehicles as motorists attempt to overtake them at the narrowing points
  • Long trucks, buses and other large vehicles may need to cross into oncoming travel lanes in order to negotiate turns at intersections with curb extensions
     

  Cost: median – high; cost can increase if drainage alteration is required.

• Traffic circles

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  A traffic circle (or mini-roundabout) is an island located at the centre of an intersection, which requires vehicles to travel through the intersection in a counter-clockwise direction around the island. 

  Advantages:

  • Very effective in reducing vehicle speeds
  • Reduces collision rates at intersections
  • When landscaped, can improve the appearance of a street
  • No effect on resident access and street sweeping
     

  Disadvantages:

  • Increase emergency vehicle response times
  • Can restrict access and turning movement of larger vehicles and buses
  • May require removal of some on-street parking
  • Traffic may be diverted to parallel streets without traffic calming measures
     

  Cost: median – high

• Other traffic calming measures

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  Other measures we may use for traffic calming:

  • Chicane: a series of curb extensions on alternating sides of a roadway, which narrow the roadway and require drivers to steer from one side of the roadway to the other to travel through the chicane. Typically, a series of at least three curb extensions is used.
  • Curb Radius Reduction: the circular curved curb which connects the tangent curb sections of two intersecting streets.
  • Directional Closure: a curb extension or vertical barrier extending to approximately the centreline of a roadway, effectively obstructing (prohibiting) one direction of traffic.
  • Diverter: a raised barrier placed diagonally across an intersection, that forces traffic to turn and prevents traffic from proceeding straight through the intersection.
  • Intersection Channelization” means the use of raised islands or bollards located in an intersection to obstruct specific traffic movements and physically direct traffic through an intersection.
  • Lane/Road Narrowing: reduced lane widths using pavement markings or other features with the intention for drivers to perceive the roadway to be less comfortable at higher speeds.
  • Lateral Shift: a roadway alignment change, introducing a ‘jog’ to the left or to the right.
  • On-street Parking: the reduction of the roadway width available for vehicle movement by allowing motor vehicles to park adjacent to the curb.
  • Raised Crosswalk: a marked pedestrian crosswalk at an intersection or mid-block location constructed at a higher elevation than the adjacent roadway.
  • Raised Median Island: an elevated median constructed on the centreline of a two-way roadway to reduce the overall width of the adjacent travel lanes.
  • Speed Cushion: a segmented speed hump which allows for the passage of larger vehicles, such as emergency vehicles or buses, without difficulty while still reducing passenger vehicle speeds.