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Transportation Division
Transportation Division

Traffic Calming in Berkeley

July 1997, revised May 1998


Traffic calming refers to a variety of physical measures intended to reduce the effect of motorized vehicle traffic in urban areas.  The first diverters were installed in 1964/65 to keep through-traffic from running alongside San Pablo Park. Berkeley began a citywide neighborhood traffic study in 1972 to address concerns regarding traffic impact on residential streets. There were numerous neighborhood meetings identifying issues and various traffic control and policy strategies. An environmental impact report was prepared. Recommendations went to the Planning Commission and then to the City Council, which adopted the Traffic Management Plan in 1975. Most of the Plan's proposed diverters and street barriers were installed by the end of that year.

In 1976, a ballot initiative to have the diverters removed failed with 44% voter support. In 1977, the "Unobstructed Access" Initiative to remove all diverters installed after July 1, 1975 also fell short, with 47% of the vote. A year of legal challenges beginning at this time resulted in a court order to remove all of the diverters since they did not conform to CalTrans standards for traffic control devices. However, the California legislature then passed a bill legalizing all existing diverters as roadway design features (California Vehicle Code 21101 (F)).

In order to allow easy installation and adjustments, the diverters consisted of specially designed concrete bollards, sometimes linked with wooden planks. Once the full effects of the barriers were known and locations were finalized, it was intended that they would be reconstructed as permanent, landscaped features. However, as cities across the state saw increasingly constrained budgets following the passage of Proposition 13, less money was available for diverter reconstruction. Thus, most of the original "temporary" diverters still consist of bollards. In some neighborhoods, residents have attempted to beautify the bollards by planting flowers in them.


There are several types of diverters in place today - semi-diverters (closing half the street) and full diverters, which either create a cul de sac or are placed diagonally across an intersection and force vehicles to turn the corner. Most full diverters have a gap between the bollards and a low steel under-carriage device, which is supposed to allow only passage of fire trucks and other high-clearance vehicles. Nearly all diverters allow bicycles to pass through on the street, while a few require bicycle passage on the sidewalk.

Speed Humps

Despite successful efforts to channel traffic out of residential blocks and onto major arterial and collector streets, auto speeds in neighborhoods remained a complaint among some Berkeley residents. In 1990 the City placed 14 speed humps on six blocks of residential streets as a pilot program. By 1996, 156 speed humps on 99 blocks had been installed. Many of the speed humps were installed at the request of the Police Department to help reduce the adverse effects of special crime related problems. In other areas, speed hump installation was initiated with a petition signed by two-thirds of the households on a block. Guideline criteria were developed and requests were prioritized to direct yearly allocations, as demand far exceeded funding. Potential locations were evaluated by a point system which took into account the volume and speed of traffic passing through the block, the number of accidents reported, the presence of schools and parks, the street width and the length of the block. The response to these slowing measures, with a few notable exceptions, was very positive.

In 1994 the Fire Department expressed its growing concern with what they saw as the rapidly spreading use of speed humps. They began opposing further construction of speed humps after complaining of slowed response times and damage to large vehicles. Compared to smaller cars, fire trucks must maintain very low speeds throughout affected areas, and passing over speed humps may cause large vehicle frames to flex awkwardly and could result in vehicle damage. Additionally, some Berkeley residents with special health problems spoke out, saying that speed humps caused them pain even when traveling over the humps at a very low speed. In response to these criticisms, City staff began working from the principle that "speed hump locations chosen must provide clear safety benefits to balance any potential negative impact" on emergency response. From a priority list of 19 blocks under consideration for speed hump construction, four critical locations were decided upon and recommended with the concurrence of both the Fire and Police Departments. Berkeley then imposed a moratorium on speed hump installation in 1995 and began an evaluation of the program. A draft report was completed in October 1997 and is available from the Planning & Development Department.  

Other Devices

Speed humps and diverters make up the bulk of the traffic calming devices in Berkeley, but they are not the only ones. The City has also installed traffic circles, curb extensions, chicanes, and textured paving. 

Traffic circles sit in the center of an intersection and are designed to force vehicles to slow down and turn right around them in order to proceed. They may be simply a cluster of bollards or a fully reconstructed and landscaped island. The recently renovated circle at Woolsey & Regent has been landscaped with rocks and a tree through the efforts of neighborhood residents. Examples of bollard-type traffic circles can be seen on California Street at Channing and at Allston.

A curb extension (or bulb-out) narrows the street at an intersection, making it easier for pedestrians to cross at the intersection while possibly slowing traffic. Chicanes are basically a series of curb extensions along a street which force drivers to shift direction as they travel down the street, thus slowing traffic. Textured pavement is designed to provide a visual or physical sensation which reminds drivers that the road is shared with pedestrians. Milvia Street between University and Cedar, known as a "slow street," has examples of curb extensions, chicanes and textured pavement, as well as speed humps.

The following table summarizes the traffic calming devices installed in Berkeley to date. The table does not include special striping, stop signs, turn restrictions, or traffic signals. For perspective, there are roughly 1,000 total blocks in the City.

Traffic Calming Device Number of Devices Number of Blocks
Speed Humps* 156 99
Traffic Circles 5 n/a
Chicanes 6 6
Curb Extensions 11 6
Textured Pavement 5 5
Street Closure 33 n/a
Full Diagonal Diverter 14 n/a
Semi-Diverter 14 n/a
* Includes two long humps (or "speed tables") on Santa Fe Avenue.
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