Vertical Devices

Vertical devices include:

Speed Humps

This speed hump incorporates a choker to increase the effectiveness.

Speed humps are paved (usually asphalt) and approximately 75 to 100 mm (3 to 4 in) high at their center, and extend the full width of the street with height tapering near the drain gutter to allow unimpeded bicycle travel. Speed humps should not be confused with the speed "bump" that is often found in private parking lots. There are several designs for speed humps. The traditional 3.7-m (12-ft) hump has a design speed of 24 to 32 km/h (15 to 20 mi/h), a 4.3-m (14-ft) hump a few miles per hour higher, and a 6.7-m (22-ft) table has a design speed of 40 to 48 km/h (25 to 30 mi/h). The longer humps are much gentler for larger vehicles.

In general, speed humps are a device of last resort. Other traffic calming solutions should be considered first. They may not be well received and can give traffic calming a bad name. Having said this, they may be the best solution is some situations, especially on long, straight residential streets where there are few intersections and no other visual cues to slow motorists.

Purpose

  • Reduce vehicle speeds; raised measures tend to have the most predictable speed reduction impacts
  • Enhance the pedestrian environment at pedestrian crossings

Considerations

  • Do not use if on a sharp curve.
  • If the street is a bus route or primary emergency route, the design must be coordinated with operators. Usually, some devices are acceptable if used prudently—one device may be appropriate and may serve the primary need (e.g., if there is a particular location along a street that is most in need of slowing traffic and improving pedestrian conditions).
  • The aesthetics of speed humps and speed tables can be improved through the use of color and specialized paving materials.
  • Noise may increase, particularly if trucks use the route regularly.
  • May create drainage problems on some streets.
  • Speed humps and tables should be properly designed and constructed to reduce the chance of back problems or other physical discomfort experienced by vehicle occupants. Tight tolerances are required during construction.

Estimated cost

The cost for each speed hump is approximately $1,000, depending on drainage conditions and materials used.

Speed Table

A raised crosswalk slows vehicles and enhances pedestrian visibility.

A "speed table" is a term used to describe a very long and broad speed hump, or a flat-topped speed hump, where sometimes a pedestrian crossing is provided in the flat portion of the speed table (see Raised Pedestrian Crossings). The speed table can either be parabolic, making it more like a speed hump, or trapezoidal, which is used more frequently in Europe. Speed tables can be used in combination with curb extensions where parking exists.

Purpose

  • Reduce vehicle speeds; Raised measures tend to have the most predictable speed reduction impacts
  • Enhance the pedestrian environment at pedestrian crossings

Considerations

  • Do not use if on a sharp curve.
  • Can be very expensive since catch basins will be needed on one or both sides of the speed table.
  • If the street is a bus route or primary emergency route, the design must be coordinated with operators. Usually, some devices are acceptable if used prudently—one device may be appropriate and may serve the primary need (e.g., if there is a particular location along a street that is most in need of slowing traffic and improving pedestrian conditions).
  • The aesthetics of speed humps and speed tables can be improved through the use of color and specialized paving materials.
  • Noise may increase, particularly if trucks use the route regularly.
  • May create drainage problems on some streets.
  • Speed humps and tables should be properly designed to reduce the chance of back problems or other physical discomfort experienced by vehicle occupants.

Estimated cost

The cost for each speed table will vary greatly depending on the width of the street and drainage considerations. The cost will vary from $15,000 to over $100,000.

Raised Intersections

A raised intersection is essentially a speed table for the entire intersection. Construction involves providing ramps on each vehicle approach, which elevates the entire intersection to the level of the sidewalk. They can be built with a variety of materials, including asphalt, concrete, stamped concrete, or pavers. The crosswalks on each approach are also elevated as part of the treatment to enable pedestrians to cross the road at the same level as the sidewalk, eliminating the need for curb ramps. Use detectable warnings to mark the entire boundary between the sidewalk and the street.

Purpose

  • Reduce vehicle speeds
  • Enhance the pedestrian environment at the crossings

Considerations

  • Don't use if on a sharp curve or if the street is on a steep grade.
  • May not be appropriate if the street is a bus route or emergency route. One device may be necessary and serve the primary need. Several raised devices may be disruptive, so other measures should be considered.
  • Speed tables and raised crosswalks and intersections can be an urban design element through the use of special paving materials.
  • Detectable warning strips at edges enable pedestrians with vision impairments to detect the crossing.
  • Care must be taken to manage drainage.

Estimated cost

Raised intersections are approximately $50,000 to $200,000, depending on drainage conditions and material used. The cost of a raised intersection is highly dependent on the size of the roads.

Raised Pedestrian Crossings

A raised pedestrian crossing is also essentially a speed table, with a flat portion the width of a crosswalk, usually 3.0 to 4.6 m (10 to 15 ft). Raised intersections and crosswalks encourage motorists to yield. On one street in Cambridge, MA, motorists yielding to pedestrians crossing at the raised devices went from approximately 10 percent before installation of the project to 55 percent after installation.

Purpose

  • Reduce vehicle speeds
  • Enhance the pedestrian environment at the crossings

Considerations

  • Don't use if on a sharp curve or if the street is on a steep grade.
  • May not be appropriate if the street is a bus route or emergency route. One device may be necessary and serve the primary need. Several raised devices may be disruptive, so other measures should be considered.
  • Speed tables and raised crosswalks and intersections can be an urban design element through the use of special paving materials.
  • Detectable warning strips at edges enable pedestrians with vision impairments to detect the crossing.
  • Care must be taken to manage drainage.

Estimated cost

Raised crosswalks are approximately $15,000 to $100,000, depending on drainage conditions and material used. The cost of a raised pedestrian crossing is highly dependent on the size of the roads.