Making Neighborhood Streets SaferRegardless 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. 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.
- 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.
Why Cut-Thru Traffic Is A ProblemAs 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.
Cul-De-Sac to Thru-Street ConversionThere 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.
“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”:
- 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
- Traffic calming measures were installed to force most traffic to obey a 25 mph speed limit.
“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 BenefitsThose who live on cul-de-sacs paid a premium 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…”
“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 ExamplesBetween 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 StreetWhile 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.”
At What Point Does Main Road Congestion Cause Excessive Cut Thru TrafficCommuters 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
Assessing the Effect of Transportation Projects on Neighborhood Street SafetyA 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 TrafficIf 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.
Ensuring Measures Really Do Calm Cut-Thru TrafficMany 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.
- 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.
Cul-De-Sacs & Quality of LifeFollowing 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:
- “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.
- 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.
- 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.
- 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.
- 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.”
Preventing Cul-De-Sac ExtensionsIf you’re concerned about a proposal to turn your cul-de-sac into a through-street then contact CEDS at 410-654-3021 or Help@ceds.org to discuss strategy options.
Why Excessive Cut-Thru Traffic Reflects Flawed Growth ManagementResponsible 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 ManagementSo 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 ZeroThe 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.”