Palos Verdes Estates Safe Neighborhood Streets Alliance

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Making Palos Verdes Estates Neighborhood Streets Safer Through Improved Traffic Calming and Pedestrian-Cyclist Measures

Nationally, neighborhood streets have some of the highest pedestrian and cyclist injury rates of all road types. California Highway Patrol data shows that 37 pedestrians or cyclists were struck by vehicles on Palos Verdes Estates streets between 2014 and 2018. The map below shows the location of these and other Palos Verdes Estates accidents.


It appears that an unusually high number of bike-involved collisions occur on Palos Verdes Estates streets.  The following graph compares 2014-2018 bike collisions in Palos Verdes with those of other Los Angeles County cities with a similar population size.  Note that of the eight cities, Palos Verdes Estates had the second highest bike-involved collision rate.

Excessive cut-thru traffic is a key factor jeopardizing the safety of our neighborhood streets. As main roads become more congested, cut-thru traffic increases.  Fortunately, there are a number of measures for making neighborhood streets safer by reducing and slowing cut-thru traffic.  Unfortunately, few Palos Verdes Estates neighborhood streets benefit from these measures.  We believe this is because we Palos Verdes residents have not provided our elected City officials with the public support they need to make greater use of raised pedestrian crossings, bike lanes, and other traffic calming measures.  So, please join with us in supporting the Mayor and City Council by signing our Palos Verdes Estates Safe Neighborhood Streets petition.

What is the Palos Verdes Estates Safe Neighborhood Streets Alliance?

The Alliance was founded by Via Zurita residents who became increasingly concerned by the growing volume of traffic speeding along their quiet neighborhood street.  For several years they sought to work with City staff and the Traffic Safety Committee to find solutions.  They were repeatedly told there was nothing the City could do.  The Via Zurita residents eventually realized the obstacle to safer neighborhood streets was more of a political-financial one than technical.  This prompted the residents to form our alliance with other Palos Verdes Estates residents wrestling with the same issue on their neighborhood streets.  For further information contact acting Alliance chair Gayne Brenneman at or (310) 722-2084.

Why does cut-thru traffic make neighborhood streets more dangerous?

Cut-thru traffic tends to operate at a higher speed, which increases the likelihood of accidents and the severity of injury for the reasons shown the following graphic:

  • a pedestrian is nearly twice as likely to die if struck by a car traveling at 30 mph compared to 20 mph,
  • as speed increases a driver’s field of vision narrows, which makes it more likely that pedestrians and cyclists will not be seen until its too late to avoid an accident, and
  • a car travelling at 30 mph requires twice the distance to fully stop compared to 20 mph.

Making Neighborhood Streets Safer Success Examples

Here are a few making neighborhood streets safer success examples:

These are but a few of many examples of successful neighborhood street safety campaigns. This goal is best achieved by mobilizing the widespread support needed to allow government to conduct a comprehensive analysis of opportunities such as those serving as the basis for Vision Zero plans. These and other measures are addressed in further detail below.

How Much Traffic Is Too Much for a Neighborhood Street

While every through-street will carry traffic from one main road to another, neighborhood quality of life suffers when the volume crosses a certain threshold.

Where is that threshold?

The table below is from a paper that appeared in the Institute for Transportation Engineers Journal. The term “environment” in the table is defined as:

“one where residents can live, work and move about in freedom from the hazards of motor traffic.”

To put these numbers in perspective, each single-family home generates one peak-hour trip and ten trips per day. These trips include the cars and SUVs driven by residents along with delivery trucks and all other traffic entering-exiting a neighborhood. One would anticipate that those who live on a residential street prefer that traffic volume remain in the good to excellent range or less than 600 vehicles per day.

At What Point Does Main Road Congestion Cause Excessive Cut Thru Traffic

Commuters begin seeking alternate routes when congestion cuts main road (arterial-collector) speed to half the free-flow (late-morning) speed. For example, if free-flow speed is 40 mph then drivers begin seeking out alternates when congestion causes average speed to drop to 20 mph. Sadly, the alternate route is frequently a through-street bisecting a residential neighborhood.

As shown in the figure below, traffic congestion is rated using a system known as Level of Service or LOS.  The rating goes from A to F.  The “half-free-flow-speed” where drivers begin seeking alternate routes in earnest lies between a Level of Service of C to D. So, to keep cut-thru traffic at a reasonable volume main road traffic congestion should not reach Level of Service D-E or F.

Traffic Calming Measures

The goal of these measures is first to slow traffic speed then reduce excessive traffic volume. Both actions make neighborhood streets safer for those crossing or walking-biking along the street and less hazardous for children playing nearby.  The following table summarizes the effectiveness of three categories of approaches for making neighborhood streets safer.

Traffic calming is divided into three areas: education, enforcement and engineered measures. While all three are vital, only engineered measures provide lasting benefits. The following discussion is based mostly on the Center for Problem-Solving Policing webpage Responses to the Problem of Speeding in Residential Areas. Other traffic calming resources can be found at:


These measures can range from a brochure to half-day programs given at local schools. Education must be the first step in any traffic calming effort. Before installing speed humps or other engineered measures on a neighborhood street it is essential that residents learn why they are needed. Residents must then have an opportunity to participate in decision-making about what approaches will be used. If done right most residents will support the effort.


Police departments have found that enforcement can be effective if four criteria are met:

  • drivers believe they’ll be ticketed if they speed,
  • it has meaningful costs to offenders,
  • police apply it generally, rather than at specific times and locations, and
  • drivers are not tipped off by cues as to when enforcement is or is not happening.

Speed cameras can be effective.  Other measures, like the speed sign to the right, only reduce speed for a few weeks. Every neighborhood seems to have a couple of residents who insist upon driving ridiculously fast. Most police departments will visit these individuals at home if alerted by other residents. This can be effective. Arresting the most severe offenders is quite effective but may require legislation giving police the authority to take this action.

Engineered Measures

These traffic calming measures range from safer crosswalks to closing off a street to through traffic.

Speed Humps span both travel lanes and are typically two- or three-inches high. They reduce speed to 20 or 30 mph. They are easier to cross and more acceptable to emergency services than speed bumps.

Traffic Circles reduce mid-block speed by 10% and intersection collisions by up to 70%. Roundabouts or rotaries are similar but are used where larger traffic volumes are anticipated and typically have two lanes of traffic in the circle. traffic circle

Chicanes are installed mid-block to narrow a street or to impart gentle curves, both of which cause drivers to slow-down. By narrowing the width of the street, chicanes also make it safer for pedestrians to cross.

Center Island Narrowing provides a safer crossing for pedestrians and can reduce speed. Some emergency service agency find this to be the most acceptable calming measure. center island

If cut-through traffic becomes excessive on a narrow, neighborhood street then one option is to close the street off at one end. Simply making a street one-way can reduce cut-through traffic by half.

Measures With Limited Effectiveness

The following measures have been found to have minimal impact upon speeding:

  • Reducing speed limits,
  • Increasing fines and penalties,
  • Stop signs, and
  • Speed bumps (as opposed to humps) and rumble strips.

Ensuring Measures Really Do Calm Cut-Thru Traffic

Many transportation agencies face a conflict when it comes to traffic calming measures. On the one hand, no one would argue that calming measures make neighborhood streets safer by discouraging cut-thru traffic. On the other hand, traffic agencies rely upon cut-thru traffic to reduce main road congestion.

This conflict can result in the design of calming measures that serve more as a pacifier rather than achieving the goal of safer neighborhood streets. For example, one study showed a substantial difference in the effectiveness of speed humps with an entrance ramp slope of less than 5%. This same study documented that speed humps spaced 82 feet apart achieved a 25% lower speed compared to a spacing of 1300 feet. Combined, a slope of >5% and spacing of 82 feet slowed traffic by an average of 5 mph more compared to speed humps with <5% slope and 1300-foot spacing.

It is not uncommon that folks say that while their neighborhood streets have speed humps or other calming measures they do not seem to have much effect on cut-thru traffic volume or speed. We suspect the poor performance is mostly due to poor design. In other words, the measures may have been designed more as pacifiers than to achieve a significant improvement in neighborhood street safety.

The recommended spacing for speed humps is every 260- to 500-feet. A typical speed hump:

  • Extends from edge of street pavement to edge of pavement,
  • Has a length of 12 feet, which
  • Means it must be at least 3.6-inches high to achieve a 5% entrance ramp slope.

If the speed humps on your street do not meet these specifications then they may be less than fully effective. Contact CEDS at 410-654-3021 or to discuss speed hump design.

Liability & Traffic Calming

Concerns about liability are occassionally voiced by cities, counties, or other jurisdictions considering the use of speed humps and other traffic calming measures.  The following text from a U.S. Federal Highway Administration guidance document shows the liability concern is exagerated when it comes to traffic calming:

“2.7 Legal Issues Liability

Few jurisdictions have been successfully sued over liability issues related to traffic calming measures. The successful lawsuits have generally been the result of improper or inadequate maintenance of signs or pavement markings, not because a traffic calming measure was determined to be inherently unsafe.

It is the duty of the public entity to make sure the roadway system is safe for the intended use of that roadway. In order to establish negligence on the part of a public entity, the injured party must establish (1) that the government agency owed a duty to that person, (2) that the duty was breached by an act or a failure to act, (3) that the breach of duty was the proximate cause of the injury or loss to the complainant, and (4) that the government had adequate notice of the dangerous condition.

In order to minimize the potential for any liability, a public agency should develop and maintain documentation of every step in the traffic calming program process.

Emergency Vehicles & Traffic Calming

Some traffic calming measures slow both passenger vehicles as well as fire, ambulance, police, and other emergency traffic.  There’s a strong correlation between how long it takes emergency service vehicle to reach a scene and the loss of life or property.  Measures which significantly slow emergency vehicles should be avoided on main travel routes while neighborhood streets can fully benefit from calming measures.  The Federal Highway Administration guidance document Effects of Traffic Calming Measures on Non-Personal Passenger Vehicles provides detailed guidance regarding Traffic Calming Measures Developed to Address Emergency Service Vehicle Delay Issues.