Speed humps are a gradual rise and fall in the pavement surface, usually with a circular profile, to a maximum height of three inches over a distance of 12 feet in the direction of travel. Typically they are installed in a series of two or more separated by a minimum of 200 feet. This type of speed hump is installed only on local residential streets. The primary purpose of speed humps is to produce sufficient discomfort to a driver to reduce travel speed to 15 mph, which should be posted as the advisory speed. The spacing of speed humps is such as to result in an average 85th percentile speed of 25-30 mph between humps, depending on the spacing. This design causes drivers to reduce speed, yet allows them to maintain control of their vehicles. Drivers of longer wheelbase vehicles, such as trucks and buses, will normally have to reduce speeds to less than 15 mph to avoid discomfort. For this reason, this type of speed hump is not usually installed on transit, truck, or emergency response routes. A primary characteristic of speed humps is their high-speed control effectiveness at a minimal cost.
Some of the advantages and disadvantages of speed humps are as follows:
Speed humps are effective in reducing the speed between humps and the degree of speed reduction depends on spacing between humps. Studies have shown that with minimum spacing of 200 feet, the 85th percentile speed is usually reduced to about 25 mph between humps.
Noise level at speed humps will increase due to braking, accelerating and bouncing.
Due to required signing and striping, there is substantial negative visual impact.
Speed humps and striping require maintenance and during resurfacing of the street, humps must be removed and reinstalled.
Speed humps will increase the response time for emergency vehicles and according to fire fighting experts, including the South County Fire Fire Marshal, they cause severe damage to the suspension systems and chassis, resulting in an increased cost for repairs.
These devices should not be installed simply because the residents request or petition. The City must have an adopted policy to be applied when a petition is submitted.
Any request for installation of speed humps must meet the following conditions:
1. The street must be a local residential street (Arterials and Collectors excluded)
2. Minimum 85th percentile speed must be 30 mph
3. Minimum 24 hour volume of traffic must be 1,200
4. Street grade must be less than 5%
5. The humps shall not be placed closer than 200 feet
6. The humps shall not be installed within 10 ft. of any manhole, fire hydrant, or a driveway
7. The street must have raised curbs or other barriers to prevent motorists from driving off the street to avoid the speed humps
8. Advance pavement legends to note “Bump” and 12 inch reflective white stripes on the speed hump (parallel to the direction of travel) must be installed
9. At least 67% of the residents on the block must sign a petition for installation of speed humps.
10. The homeowners and residents on both sides of the street where a hump is to be installed must agree in writing.
11. All traffic calming devices, especially Speed Humps, divert traffic to neighboring streets. Therefore, the Traffic and Transportation Commission should consider the impact on other streets and the residents of all impacted streets should be informed before a final decision is made.
12. The property owners/residents must pay 100% cost of construction, including the required striping.
13. The property owners/residents will not be responsible for maintenance of the humps and the striping. In case of necessity for removal and reinstallation, due to street resurfacing, property owners/residents will not be responsible for the cost.
14. Speed humps must be installed in accordance with design and specifications approved by the Public Works Director.