Raised Crosswalks

(Continued from Bumps, Humps, & Other Raised Pavement Areas)

Raised crosswalks are essentially broad, flat-topped speed humps that coincide with pedestrian crosswalks at street intersections. The crosswalks are raised above the level of the roadway to slow traffic, enhance crosswalk visibility, and make the crossing easier for pedestrians who may have difficulty stepping up and down curbs.

Raised Crosswalks Design Considerations:
• Can be constructed of brick, concrete block, colored asphalt or cement, with ramps striped for
better visibility.
• Raised crosswalks are applicable:
(1) On roadways with vehicular speeds perceived as being incompatible with the adjacent residential                       land uses.
(2) Where there is a significant number of pedestrian crossings.
(3) In conjunction with other traffic-calming devices, particularly entry treatments.
(4) On two-lane or fewer residential streets classified as either “local streets” or neighborhood
collector streets.”
(5) On roadways with 85th percentile speeds less than 45 mph.

Next… Intersection Humps/Raised Intersections

The most fundamental traffic-calming goal is to reduce the speed of vehicular traffic . With the reduction of speed, the following important objectives can be realized:

1. Improved “feel” of the street.

This objective calls for increased community involvement in and “ownership” of the street. If people feel more comfortable on the street, they are more likely to walk or bicycle there and to engage in other street oriented activities with their neighbors. A key aspect of achieving this objective is reducing the perceived threat of danger from motor traffic.

2. Enhanced aesthetic values and a sense of nature.

Several traffic-calming techniques, such as street landscaping, pedestrian amenities, and reclamation of roadway areas can serve as community open space.  Not only do these techniques make the neighborhood more attractive, but they also break up long, uninterrupted street vistas conducive to speeding and convey the message that “this is a pedestrian place.”

3. Reduced crime.

It’s harder to make a speedy getaway if a fleeing felon has to deal with speed humps, woonerfs, and traffic circles. It’s harder to get away without being spotted if there are “eyes on the street” – if the street is a positive, community focus.

4. Equitable balance among transportation modes.

With reduced motorist speeds, safety is improved. Pedestrians and bicyclists have more time to detect and avoid motor vehicles. Traffic calming sends the message that “motor vehicles don’t exclusively
OWN the roadway” – that other modes have equal rights. Studies that evaluate traffic-calming improvements show increased levels of walking, bicycling, and transit use following installation.

5. Increased safety/decreased severity of injury in traffic crashes.

With reduced speeds comes a significant reduction in the number and severity of crashes involving motor vehicles. Traffic-calming facility evaluations uniformly show fewer crashes, fewer fatalities, and less severe injuries.

6. Improved air quality and noise levels.

Slower moving vehicles make less noise and, generally, emit fewer pollutants.

7. Decreased fuel consumption.

With more trips made by walking, bicycling, and transit, and with slower traffic speeds, fuel consumption reductions of 10 to 12 percent have been reported.

8. Continued accommodation of motor vehicle traffic.

An important objective is the continued accommodation of motor vehicle traffic. Although traffic calming shifts the balance among travel modes, this shift should not result in severely restricted traffic volumes or in shifting traffic problems from the traffic-calmed area to other streets.

The City of Austin, Tx has an excellent FAQ section about Speed Humps.

I’ve reproduced some of that faq here in this post but you really should visit this page where the original post occurs to get the full list of speed hump Frequently Asked Questions that they’ve posted.

These frequently asked questions about speed humps are a great resource to have at your fingertips if you are responsible for designing or specifying speed humps or even if you are considering speed humps for your own project.

Q. - Why do we have speed humps?

A. - Speeding on residential streets is a common complaint of concerned citizens. Although enforcement of speed limits by police departments is an effective means of reducing speeds, limited resources do not allow such enforcement on a regular and permanent basis. Research has shown that speed humps are an effective approach to slowing down traffic on residential streets.

Q. - What is a speed hump and how is it different from a speed bump?

A. - A speed hump is a gradual rise and fall of the pavement surface along the roadway extending across the pavement width. Generally, speed humps used on residential streets are 12 to 22 feet long with a maximum height of 3 to 4 inches. Speed “humps” are different from speed “bumps”, which are seen in many private parking lots.

A speed bump is abrupt, having a height of 3 to 4 inches over a length of 1 to 3 feet. Speed bumps cause most vehicles to slow down to almost a stop to go over it. Speed humps, on the other hand, are designed so most vehicles can go over them at 20 mph without causing driver discomfort.

Q. - How are speed humps effective in controlling speeds?

A. - Speed humps cause a gentle vehicle rocking motion that causes driver discomfort, thus resulting in most vehicles slowing down to 20 mph at each hump. Depending upon street geometry, speed humps are placed every 200 to 600 feet. The presence of speed humps causes drivers to slow down at the humps and in between properly spaced successive humps. Speed humps have the advantage of being self-enforcing. They are sometimes referred to as “sleeping police officers”.

Q. - What will happen if I go over speed humps at high speeds?

A. - At high speeds a speed hump can cause significant driver discomfort. At such speeds it can act as a bump and jolt the vehicle’s suspension and its occupants or cargo.

Q. - Do speed humps reduce cut-through traffic?

A. - The primary purpose of speed humps is to reduce the speeds of vehicles traveling along a roadway. Traffic diversion due to speed humps is a side effect which may or may not result. A possible disadvantage of speed humps is that motorists may avoid the speed humps by using other nearby streets in the area.

Q. - How is a driver warned of the presence of speed humps?

A. - On any street with speed humps, warning signs such as “Road Humps Ahead” are placed before the beginning of each series of humps. These signs also indicate the speed at which drivers are advised to travel over the hump. To be properly visible, the speed hump is marked with diagonal white stripes.

Q. - Can speed humps be placed on any street?

A. - Speed humps are placed only on residential streets with not more than two lanes and with a speed limit of 30 mph or less. For safety reasons, speed humps are not installed within sections which are curved or where the street slopes uphill/downhill.

Speed humps are not typically installed on streets where emergency facilities are located. The Department of Public Works and Transportation communicates with the Austin Fire Department and Emergency Medical Services to ensure that the speed humps will not greatly impact their services. Increases in response time of approximately 2-10 seconds per hump may exist with the installation of speed humps.

This is not by any means a comprehensive list of FAQ’s about speed humps but it certainly covers the basic questions asked about speed humps.  The answers too are as related to the public works division of a local US city government but for the most part these answers to frequently asked questions about speed humps can aid in understanding the issues involved with speed humps.

Traffic Calming? What is it?

According to our friends at the Instutute of Transportation Engineers:

Traffic Calming is the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior and improve conditions for non-motorized street users.¹

Traffic calming goals include:

• increasing the quality of life;
• incorporating the preferences and requirements of the people using the area (e.g., working, playing, residing) along the street(s), or at intersection(s);
• creating safe and attractive streets;
• helping to reduce the negative effects of motor vehicles on the environment (e.g., pollution, sprawl); and
• promoting pedestrian, cycle and transit use.¹

Traffic calming objectives include:

• achieving slow speeds for motor vehicles,
• reducing collision frequency and severity,
• increasing the safety and the perception of safety for non-motorized users of the street(s),
• reducing the need for police enforcement,
• enhancing the street environment (e.g., street scaping),
• encouraging water infiltration into the ground,
• increasing access for all modes of transportation, and
• reducing cut-through motor vehicle traffic.

¹Lockwood, Ian. ITE Traffic Calming Definition. ITE Journal, July 1997, pg. 22.

This excellent article just about says it all.  It not only defines what traffic calming is it also provdes the objectives and goals of traffic calming devices.

As I am sure you can tell from this excerpt, the ITE traffic calming website is an excellent resource to use when you need information about speed bumps, speed humps, speed tables or any other type of traffic calming device.  So check it out!

This Maine Dept of Transportation article contains an excellent summary comparison of Speed Bumps versus Speed Humps which is presented here.

Speed Humps:

• Are a gradual raised area in the pavement surface extending across the entire travel width
• Typically, 3 to 4 inches in height with a travel length of 12 to 15 ft
• Have evolved from extensive research & testing
• Create a gentle vehicle rocking motion which results in most vehicles slowing to 15 mph at each hump and 25 to 30 mph between properly spaced humps in a system
• Need to be designed and installed with proper planning and engineering
• Effective at controlling speeds without creating accidents or imposing unreasonable or unacceptable safety risks

Speed Bumps:

• Are an abrupt raised area in the pavement surface
• Effective at controlling speeds on low volume, low speed roads, especially private driveways & parking lots
• Typically, 3 to 6 inches in height with a travel length of 6 in. to 3 ft
• Cause significant driver discomfort at typical residential speeds.
• Cause vehicles to slow to 5 mph or less at the bump.
• Maintenance headaches especially for plow trucks.

And as always… beware of speed bumps on the road of life!