Traffic Engineering Division
The Traffic Engineering Division is responsible for establishing and operating a safe and efficient transportation network. This includes the city streets and crosswalks, traffic control devices, bicycle facilities, curb space, and roadway signs and markings. Please continue reading to find out more about common traffic issues and requests and the City’s stance on each topic:
Speed Limits and Speeding
Speeding on residential roads is one of the top complaints reported to the Department of Public Works. Studies show that most motorists travel above the 25 mph speed limit on residential roads, and that those who exceed the speed limit come from all age groups. Often residents speed because they feel more familiar and comfortable on roadways they travel regularly, and others may use them as short cuts.
Many studies have concluded that drivers are influenced by the type of street and the current traffic conditions, and not the posted speed. In other words, changes in posted speed limits have little to no effect on vehicle speeds.
There are several types of roadways in which the speeds are set by the California Vehicle Code (“prima facia” speed limits apply). The speed limit on local, residential roads is 25 mph. All other speed limits must be established based on engineering studies which look at roadway conditions, accident records and the existing speeds at which most vehicles travel. Setting unreasonably low speed limits has two negative effects: (1) makes violators out of otherwise law-abiding drivers; and (2) creates difficult situations for the police and community, especially when citations are not upheld in court.
Under the right conditions STOP signs can play an important role in traffic safety, when installed at an unsuitable location they can create more problems than they solve. National standards have been established to determine when STOP signs should be installed. These standards consider traffic speed, the number of vehicles, pedestrians and bicycles, intersection sight distance, and the frequency of gaps in traffic to allow safe vehicle entry or pedestrian crossing.
Studies have shown that when all-way stops are installed at locations that do not meet requirements, they do little to slow traffic and can actually make the intersection less safe. Unwarranted stop signs are frequently ignored by drivers on the main street, putting pedestrians and cross-traffic at a higher risk. Numerous studies nationwide have shown that speeds within a block of unwarranted stop signs are largely unaffected. Naturally, motorists have to slow down when approaching a stop sign, but they often speed up quickly to make up for lost time. In addition, stopping and starting causes an increase in tire and engine noise and an increase in air pollution.
Speed humps are a common request when someone has speeding concerns in their neighborhood. While speed humps may help reduce speeds on a roadway, some potential drawbacks include:
- Noise levels increase at the hump due to deceleration/acceleration and the noise of a vehicle going over the humps
- Slows emergency vehicle response times
- Potential to divert traffic to other local streets, thus moving the problem
- Some residents may find the additional signage and striping associated with speed bumps as unattractive
- May not change driver behavior and result in other dangerous driving behavior, such as going “off road” to avoid the humps
- More potential for neighborhood conflicts since there may not be 100 percent support for the speed hump installation
- Potential vehicle damage if traversed at high speeds
- Potential reduced property values
Children at Play
Children at Play signs are not recognized by the State of California or the Federal government as official traffic control devices, and are therefore not installed on public streets in the City of Petaluma.
Traffic studies have shown that these signs do not increase driver awareness to the point of reducing vehicle speeds or pedestrian accidents. In fact, placement of the signs may actually increase the potential for accidents by providing a false sense of protection that does not exist and cannot be guaranteed.