Regardless of where you live in the U.S., CEDS can help with making neighborhood streets safer by preventing excessive cut-thru traffic or winning the installation of speed humps and other traffic calming measures.  To learn more read on or contact CEDS at 410-654-3021 or Help@ceds.org for an initial no-cost discussion of strategy options.  Also, consider participating in a CEDS one-hour online workshop on what works with regard to making neighborhood streets safer.

Click this sentence to see examples of how we’re making neighborhood streets safer.

Of all our roads, neighborhood streets have the highest accident rate. And these accidents involve a substantially higher percentage of pedestrians and cyclists when compared to those occurring on other roads. 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. Main road congestion is a result of poorly managed growth. There are a number of measures for making neighborhood streets safer by reducing cut-thru traffic. Other measures can then prevent future growth from threatening safety once again.

The map above shows a road network typical of many residential areas. As main roads (blue arterials and gold collectors above) become increasingly congested, drivers seek out ways for getting around traffic jams. Unfortunately, the alternative usually involves a neighborhood through-street like those in red and gold above. This cut-thru traffic makes neighborhood streets noisier and more dangerous.

Cut-thru traffic tends to operate at a higher speed, which increases the likelihood of accidents and the severity of injury because as the graphic below shows:

• 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 driver field of vision narrows, which makes it more likely that pedestrians will not be seen nearby 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.

To measure the speed and volume of traffic on a street see the CEDS Traffic Evaluation Procedures.

Of even greater concern are situations where traffic volume increases because a court or other cul-de-sac (dead-end) street is turned into a through-street.

Congested roads and rising neighborhood cut-thru traffic are a result of poorly managed growth. In this webpage we’ll explain how to resolve both in ways that can make neighborhood streets safer while accommodating a reasonable amount of growth. Contact CEDS at 410-654-3021 or Help@ceds.org if you have any questions or would like our assistance making your street safer.

Why Cut-Thru Traffic Is A Problem

As traffic volume increases on a neighborhood street so does vehicle speed, accident frequency, noise, and even crime. All of these impacts then decrease property value.

Table 1, below, is from a Texas Transportation Institute report and shows that local roads/streets in urban areas have the highest crash (accident) rate. In an urban setting, most of these local roads would be residential or neighborhood streets.

Table 1, shows that neighborhood streets are our most dangerous. Research has determined that those using neighborhood streets to avoid main road congestion tend to drive at a higher speed. The combined effect of cut-thru traffic increased speed and volume makes a neighborhood street even more dangerous.

It is generally true that as traffic volume increases, the value of homes along a street declines. This is especially true for those living on courts and other cul-de-sac streets where homes can sell for up to 20% more than those located on through streets.

Cul-De-Sac to Thru-Street Conversion

There is a large body of literature touting the benefits of maximizing street connections. This research has prompted many local planning agencies to require conversion of cul-de-sacs to thru-streets. Usually this opportunity only arises when a proposed development project abuts a cul-de-sac neighborhood. An example of this situation is pictured below.

Burnt Hills Drive is located in Queensbury, NY. Note that in 2015 Burnt Hills Drive was a cul-de-sac. It was then converted to a thru-street when new homes were built. After clicking on the map above to get a closer view you’ll see that Burnt Hills Drive became the only connecting street along a three-mile stretch between Luzerne Road and Upper Sherman Avenue and between I-87 and Route 58. As a result whenever the two east-west streets become heavy drivers use Burnt Hills Drive in hopes of bypassing the congestion.

There were two dozen homes on Burnt Hills Drive before the connection. These homes would have generated about 25 peak-hour trips. A recent traffic study revealed that peak-hour traffic on Burnt Hills Drive is now more than ten times higher! Burnt Hills Drive residents are now seeking to win the cooperation of their elected representatives to employ measures to reduce and slow down the large volume of cut-thru traffic.

The irony of the Burnt Hills Drive situation is that the local comprehensive plan contained the following text regarding cul-de-sac to thru-street conversions:

“Despite the advantages that connections bring, it is not practical or even necessary to force every residential subdivision to open up roads to its neighbors. Rather, it is important to establish the right connections between the right places.”

Here’s an example of a “right connection”:

1. If funds had been available to convert a number of other cul-de-sacs to thru-streets between Route 58 and I-87 so the impact to any one neighborhood would be minimized, and
2. Traffic calming measures were installed to force most traffic to obey a 25 mph speed limit.

The reality is that local officials have resisted installing traffic calming measures on Burnt Hills Drive post-connection. So if they cannot afford these relatively inexpensive safeguards it is unlikely they would have had the funds to convert other cul-de-sacs to thru-streets.

Of course local officials should have required that the developer who profited from the Burnt Hills Drive connection pay for installing calming measures. Why this was not done is unclear even though the following comprehensive plan text clearly called for this:

“Any new automobile connections must be accompanied by specific and extensive traffic calming interventions to mitigate the possibility of increased traffic on some residential streets.”

Finally, in most existing communities cul-de-sacs are so numerous that conversions of all to thru-streets is exceedingly unlikely. It is only in the few instances where proposed development abuts a cul-de-sac neighborhood that conversion is likely. In other words, a few neighborhoods fall victim to an unrealistic policy.

However, it would be far less expensive and beneficial to use development projects to enhance neighborhood quality of life by creating connecting pedestrian-cyclist paths. As the last bit of irony, the following town comprehensive plan text encouraged this:

“Pedestrian and bike connections can achieve many connectivity goals at a fraction of the cost.”

Following is a description of the many benefits enjoyed by cul-de-sac residents.

Cul-De-Sac Benefits

Those who live on cul-de-sacs (dead-end streets) paid a premium of 20% to as much as 29% to enjoy the enhanced quality of life motivating their choice.

Converting cul-de-sacs to through streets interferes with the close neighbor relations that adds so much to quality of life. For example, one sociologist found that:

“people who live in traditional bulb cul-de-sacs have the highest levels of attitudinal and behavioral cohesion (covering both how they feel about their neighbors and how much they actually interact with them). People who live on your average residential through-street have the lowest levels…”

For parents living on courts or other low-volume streets, a rise in traffic volume may increase anxiety about allowing children – particularly younger kids – to play outside. Children between the ages of 5 and 9 are particularly at risk to traffic-caused injury. Converting cul-de-sacs to through-streets robs both children and their parents of a sense of safety and freedom many cherish.

With regard to crime, one study noted that:

“Furthermore, hierarchical, discontinuous street systems have lower burglary rates than easily traveled street layouts; criminals will avoid street patterns where they might get trapped. For example, the troubled Five Oaks district of Dayton, Ohio, was restructured to create several small neighborhoods by converting many local streets to cul-de-sacs by means of barriers. Within a short time traffic declined 67 percent and traffic accidents fell 40 percent. Overall crime decreased 26 percent, and violent crime fell by half. At the same time, home sales and values increased.”

Making Neighborhood Streets Safer Success Examples

Between 2013 and 2016, New York City reduced traffic-related fatalities by 23% while nationally they increased by 7%.

Speed humps and tables have reduced crashes on neighborhood streets by up to 45%.

Holding back left-turning traffic for 3-7 seconds at signalized intersections has reduced pedestrian injuries by 60%.

A sizable portion of cut-thru traffic can be attributed to apps that steer drivers from congested main roads onto neighborhood streets. Very frustrated officials in one town felt they had no choice but to close off neighborhood streets to rush hour cut-thru traffic.

These are but a few of many examples of measures that can make neighborhood streets safer. 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 detached home generates one peak-hour trip and ten trips per day. This includes not just the cars and SUVs driven by residents but 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. In other words, land use decisions should not cause traffic volume to exceed 600 vehicles per day on a neighborhood street.

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 (mid-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. Of course the alternate route is frequently a through-street passing through a residential neighborhood.

As shown in the figure below, traffic congestion is rated using a system known as Level of Service ranging from A to F. That “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.

Best Options for Reducing Congestion

Unfortunately, few plans present these ratings in a way that makes it easy for tax payers to see how projects will make their lives better by improving mobility.  One of the exceptions is the Metro Washington, D.C. Plan which was based in part on the following graphic showing that ten project categories would reduce congestion by 2% to 24%.
Note that the projects involving new roads or adding lanes to existing highways are among the least effective.  To understand why, see the 11-minute video Why Is It So Hard to Fix Traffic?

Assessing the Effect of Transportation Projects on Neighborhood Street Safety

A number of states and localities use a level of service system to rate the impact of increased motor vehicle traffic on pedestrian or cyclist safety.  One of the earliest rating systems was developed by the Florida Department of Transportation.

The systems rate streets on a scale of “A” to “F” for walking-cycling suitability.  A rating of “A” to “C” is considered acceptable while “D” to “F” indicates a street is increasingly less suited for walking-cycling.  The rating declines as traffic volume and speed increases if all other factors remain the same.  In other words, an increase in traffic volume could lower the suitability of a street for walking-cycling.  If the increase is due to cut-thru traffic, which tends to operate at a higher speed, then the negative effect on suitability will be compounded.

The walking-cycling level of service system should be used to assess the effect of all transportation projects on neighborhood street safety.  The following Walkable Communities posters illustrate the factors making for a more pedestrian or cyclist friendly street.

Reducing Existing Cut-Thru Traffic

If traffic on your street exceeds the good to excellent range (300-600 vpd) given above, then consider calling for one or more of the many measures listed proven to reduce both cut-thru speed and volume. The permanent measures given below are more effective and long-lasting. For assistance in forming a traffic management strategy for your street(s) contact CEDS at 410-654-3021 or Help@ceds.org.

Roundabouts & Rotaries Reduce Main Street Congestion & Cut-Thru Traffic

Converting an intersection from one controlled by traffic lights or stop signs to a roundabout or rotary (aka traffic circle) provides substantial benefits:

• Main road traffic congestion can be reduced by 50%, which reduces cut-thru traffic on nearby neighborhood streets.
• About a fourth of fatal traffic accidents occur at signal- or stop-controlled intersections. Converting these intersections to a rotary-roundabout reduces fatal accidents by 75%.
• A lot of fuel is burned and air-pollution produced while drivers are idling at a red light. A rotary-roundabout eliminates this waste, expense, delay and climate-changing greenhouse gas emissions.
• It costs less to convert a stop-controlled intersection to a roundabout-rotary than converting it to traffic signals.
• Converting a signal-controlled intersection to a rotary-roundabout saves money, as well as lives, in the long run.

For further detail see:

• The Insurance Institute for Highway Safety (IIHS) Roundabouts webpage, and
• Freakonomics podcast 454 Should Traffic Lights Be Abolished?.

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 making neighborhood streets safer. 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 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 does not meet these specifications then they may be less than fully effective. Contact CEDS at 410-654-3021 or Help@ceds.org to discuss.speed hump design

Cul-De-Sacs & Quality of Life

Following is a summary of research demonstrating why cul-de-sacs and other dead-end neighborhood streets should not be converted into through-roads.

In a paper entitled The Cul-de-sac Effect: Relationship between Street Design and Residential Social Cohesion, published in the Journal of Urban Planning and Development, Volume 141 Issue 1 – March 2015, sociologist Thomas R. Hochschild reported:

“This study utilized a quasi-experimental design to assess differences in residential social cohesion for residents of “bulb” cul-de-sacs, “dead-end” cul-de-sacs, and through streets. My data reveal that bulb residents experience the highest levels of attitudinal and behavioral cohesion, followed by dead-ends, then through streets.”

5 Benefits of Cul-De-Sacs:

1. “Eliminates Through Traffic: Cul-de-sacs are dead-end streets. There is no drive-through or commuter traffic speeding down the street. Because there is no reason to pull into a cul-de-sac unless your destination is on that street, the flow of traffic is reduced.
2. Safer Streets For Residents and Children: Due to the reduction of traffic on a cul-de-sac, the streets are safer for children and residents on the street. Cars also tend to drive much slower on a cul-de-sac because they are approaching their destination. They realize the street is a dead-end and this adds to the safe environment for families and their kids.
3. Promotes A Neighborly Environment: A cul-de-sac emphasizes the closeness of homes and families. With a quieter street, the opportunity for playing on the sidewalk, front yard and even the street is more appealing. This environment promotes more interaction with other Fountain Hills residents and invites block parties and other cul-de-sac events creating a closer bond between the families.
4. Lower Burglary and Vandalism Rates: In addition to the safety provided by the lack of speeding traffic, the homes on cul-de-sacs themselves experience lower crime rates. With more street play and activity, the families are more connected and this adds protection to the homes. Criminals are denied easy access and egress and with the increased visibility, cul-de-sacs have a significantly lower rate of burglary than their neighbors on the drive-through streets.
5. Increased House Values: All this adds up to increase property values for Fountain Hills homes situated on a cul-de-sac. Due to the layout of the street, more homes can take advantage of the extra space of a pie-shaped lot. The lifestyle and curb appeal of a quiet street appeal to buyers and results in higher sales prices. Corner lots are particularly desirable.”

Reconsidering the Cul-De-Sac: “Residents also preferred the cul-de-sac as a place to live, even if they actually lived on a through or loop street. People said they felt cul-de-sac streets were safer and quieter because there was no through traffic and what traffic there was moved slowly. They also felt they were more likely to know their neighbors. One resident’s comment was typical: “Our pets and kids are safer when there is a no-outlet street; you feel kidnapping is less likely—there is more of a sense of neighborhood.” Thus, the study generally corroborated earlier transportation research on the values of a hierarchical discontinuous street pattern. It also supported claims that cul-de-sacs are more frequently and more safely used by children.

The Benefits of Living in A Cul-De-Sac: “Because cul-de-sacs tend to have fewer homes than traditional streets, it is easier for people to get to know their neighbors in the cul-de-sac. Cul-de-sacs also are a natural place for neighbors to plan block parties or picnics because with proper permits from the local authorities, a cul-de-sac can be blocked off to any incoming or outgoing traffic during the block party. Homes in a cul-de-sac generally face outward toward the other homes, creating a greater sense of community for the residents as they can see their neighbors’ front doors from their own.”

Residential Street Design and Play: A literature review of policy, guidance and research on residential street design and its influence on children’s independent outdoor activity: “Both traffic speed and volume have been found to have an effect on how streets are used. Appleyard’s study of three similar streets in San Francisco showed that residents’ quality of life was measurably affected by the volume of traffic in the street (Appleyard, 1981). Those living on a light-trafficked street knew more of their neighbors, felt a greater sense of belonging and were more familiar with its physical features. The study was replicated on residential streets in Bristol in 2011 and the findings resonated strongly with Appleyard’s (Hart & Parkhurst, 2011).”

Preventing Cul-De-Sac Extensions

If you’re concerned about a proposal to turn your cul-de-sac into a through-street then contact CEDS at 410-654-3021 or Rklein@ceds.org to discuss strategy options.

Take a look at the streets highlighted black, above. About a fourth to a third of the streets are courts or other cul-de-sacs. The same is probably true for most of the U.S.

Those who live on these cul-de-sacs paid up to 20% more for the increased safety and tranquility of these low-volume streets. It is understandable then that cul-de-sac residents become irate when a proposal is made to open their street to cut-thru traffic. It’s even more infuriating when this is done to allow an adjacent property to be developed.

Usually the justification for the extension is to provide a second means of emergency vehicle access should the main entrance ever be blocked by a downed tree, floodwaters, vehicle accident, etc. Another justification is to increase road connectivity to relieve congestion on main routes. The relief is achieved, of course, by increasing neighborhood street cut-thru traffic.

As stated above, increasing neighborhood cut-thru traffic to relieve congestion is a symptom of poor growth management. While a second means of emergency access is certainly a legitimate need, there are ways of accommodating this need without forcing residents to sacrifice the safety and tranquility of their neighborhoods.

Before a cul-de-sac conversion is considered, all other options must be exhausted.

CEDS has helped a number of communities with this issue. We can frequently find an alternate, second access such as creating a new road off an existing collector or arterial that prevents neighborhood impact.

If an alternate access is not available then other options must be considered. If cul-de-sac extension is the only means for creating a second access and the second access is genuinely needed for public safety, then consideration should be given to gating the access so it can only be opened by fire, ambulance, police and other emergency services personnel.

To see an example of how CEDS can help you protect your cul-de-sac from being turned into a through-street click on: Preventing Cul-De-Sacs From Becoming Through Roads.

If for some reason an emergency-access-only gate is not an option, then a number of measures should be considered that reduce cut-thru traffic speed, volume and crash rates, like the speed humps referenced in the table above. Public officials may argue that these measures interfere with snow-plowing and emergency vehicle travel time. Rarely though do the benefits of the measures come up in these arguments.

As stated at the beginning of this webpage, neighborhood streets have the highest accident rate of all road types. Homes located on cul-de-sacs are valued for up to 20% more, which generates higher property-tax revenue. It’s simply wrong to ask people to sacrifice the safety and tranquility of their neighborhood without exhausting all other options. I suspect that if elected officials were aware of the higher accident rates, lower tax revenue, and injustice then more responsible policies would be adopted with regard to the conversion of cul-de-sacs into through streets.

How Much of the Traffic on Your Street is Cut-Thru?

Each home adds one vehicle (or trip) to the morning or evening peak traffic hour.  The aerial below shows seven homes on Bushey Road between Liberty Road (north) and Old Liberty Road (south).  Note Bushey Road has seven more morning peak-hour trips at the north end then at the south where it intersects Old Liberty.  But there’s another 43 morning peak-hour trips coming from those turning north onto Bushey Road from Old Liberty.  So, 82% of morning traffic is from commuters using Bushey Road to reach Liberty Road – a main highway.  For guidance on doing a traffic count see: CEDS Traffic Impact Evaluation Procedures.

Most neighborhood street systems are not as simple as that depicted above.  Some have connecting streets which in turn connect to highways.  Others have a mix of single-family detached homes, townhouses or apartments which each respectively add about 1.0, 0.5, and 0.4 peak-hour trips.  Nevertheless, one can still get a rough idea of cut-thru traffic volume even in these complex situation using the peak-hour method described above for Bushey Road.

Why Excessive Cut-Thru Traffic Reflects Flawed Growth Management

Responsible growth management seeks to prevent congestion from reaching the threshold (Level of Service D-E or F) where cut-thru traffic harms neighborhood quality of life.

Ironically, increasing main road congestion seems to create pressure on public officials to engage in two practices that exacerbate neighborhood cut-thru traffic:

• Allowing cul-de-sacs to be converted into through streets, and
• Resisting calls for speed humps and other measures that would slow cut-thru traffic speed-volume.

Winning Responsible Growth & Traffic Management

So how would responsible growth management prevent main road congestion from reaching the point where rush-hour cut-thru traffic becomes excessive? More importantly, how can you provide elected officials with the public support they need to manage growth responsibly?

Responsible growth management begins with a plan that identifies existing and future congestion problems then recommends solutions. Next elected officials must allocate the funds required to make the infrastructure improvements many solutions require. Finally, Concurrency and Adequate Public Facilities Ordinance (APFO) laws must be in place to prevent additional growth from being approved before solutions are fully implemented.

CEDS has found that far too many growth management plans fail to show both existing and future congestion. Without this information plan readers are left in the dark as to whether growth will make their streets safer or more dangerous. To see what a good plan should provide see the Traffic Congestion section of the CEDS Comprehensive Plans, Master Plans & Quality of Life Growth Management webpage.

Infrastructure improvements frequently come years after congestion has become excessive. Instead, the infrastructure projects must be included in capital improvement plan then fully funded, preferably through the use of impact fees.

Far too many APFO-Concurrency laws are so poorly written or enforced as to be ineffective. This leaves local residents wondering if congestion is inevitable. Of course it isn’t. A common flaw is that the congestion cut-off is set well beyond the point where cut-thru traffic becomes serious.

Earlier this point was given as when average speed is cut in half and Level of Service drops below C-D. Urban-suburban growth restrictions should kick in and postpone development which would add traffic to roads that will be at or below Level of Service D-E. Instead the cut-off is frequently set at the point where average speed is reduced by 75% and congestion reaches Level of Service E-F.

Winning responsible traffic and growth management begins with homeowner and other neighborhood associations taking the following actions:

• Identify issues affecting the safety and tranquility of your streets,
• Develop solutions for each issue (see CEDS Traffic webpage),
• Employ Politically Oriented Advocacy to provide elected officials with the public support needed to implement the solutions, then
• Form a coalition with kindred groups throughout your town, city or county to create the political clout needed to effectively advocate for better growth plans, full funding of solutions, and effective, fully enforced APFO laws so growth is postponed until it can be accommodated without making neighborhood streets more dangerous.

Vision Zero

The Vision Zero website describes this concept as…

“…a strategy to eliminate all traffic fatalities and severe injuries, while increasing safe, healthy, equitable mobility for all. First implemented in Sweden in the 1990s, Vision Zero has proved successful across Europe — and now it’s gaining momentum in major American cities.”

Vision Zero seeks to achieve this goal by…

• “lowering speed limits
• redesigning streets,
• implementing meaningful behavior change campaigns, and
  enhancing data-driven traffic enforcement.”

Consider urging your local elected officials to adopt a Vision Zero plan for your village, borough, town, city or county. For further detail visit the Vision Zero resources page at: https://visionzeronetwork.org/resources/