Speed Humps

• Vertical speed control measures.
• Rounded raised areas of pavement across the lane of travel.
• Designed to allow vehicles to traverse them safely and encourage vehicles to proceed at or below the posted speed limit. (Usually around 20mph)
• Ideal for residential applications.

Typical Design:

• Speed humps are generally 12 to 22 feet in length, 3 to 4 inches high, and extend across both lanes of travel. The desired design speed determines the dimensions of the speed hump.
• The design speed is usually around 20mph.
• Speed humps usually have a taper and space on each side by the curb to allow for drainage, but not wide enough for motorists to cross the hump with one wheel in the gutter.
• The most popular shape of speed hump in the United States is the sinusoidal profile known also as the Watts profile (Designed and tested by the Transport and Road Research Laboratory (now TRL) in Great Britain.). Other shapes: Circular & Parabolic.
• The Institute of Transportation Engineers has design recommendations.(2)
• The Pennsylvania Department of Transportation has design recommendations.(3)

The Flat-Top is a speed table.

Placement Issues:

• Speed humps are usually used at mid-block locations and placed in a series, with a distance of about 300 to 600 feet between measures.
• Fire trucks experience an approximate delay of 3 to 5 seconds per hump.
• Ambulances with patients can experience up to 10 second delays per hump.

Typical speed hump in Howard County MD.

Approximate Cost:

• Installation costs for speed humps are between $1,500 and $3,500, depending on the width of the road.(3)

Comments:

• A speed HUMP is not a speed BUMP for a few reasons:
  • Speed humps are much longer than speed bumps.
  • Speed bumps produce the greatest driver discomfort at low speeds; at higher speeds the suspension is able to absorb the impact before the body of the car reacts.
  • A speed hump has a design speed greater than a speed bump. The speed bump is commonly employed in parking lots where speeds are very low, while a speed hump is used on a roadway with the intention of keeping vehicles at a safe, constant traveling speed.
• According to traffic engineers and planners, speed humps do not have adverse effects on snow plows. If the hump is properly installed, the plow should glide over the hump.
• Speed humps work well when installed in conjunction with necking measures.
• Considerable attention should be given to aesthetics when designing speed humps.

Hump elevation and gutter clearance.