Traffic Calming (Traffic Taming)

The Delaware Valley Regional Planning Commission (website) is a regional agency that advises on policy and capital funding issues concerning transportation, economic development, the environment, and land use. They select two projects each year and I am pleased that they have chosen Bethlehem Pike this year for a "taming traffic" study, which they are funding. I hope you will be involved throughout the process that can lead to a more pedestrian-friendly, driver-friendly Bethlehem Pike within the near future. See Bethlehem Pike for link to the draft Traffic Taming study.

Below, I have extracted some key portions of the Pennsylvania's Traffic Calming Handbook to give you, the non-professional concerned citizen, an overview of the techniques, challenges, and outcomes of traffic calming. The full document is here [large, pdf].

Source: City of Iowa City, Iowa

Graphic showing sample traffic-calming techniques, including traffic circle, bulb-out, semi-diverter, diagonal diverter, chicane, speed humps, on-street parking, and choker. Many other techniques are available.

What Is Traffic Calming?

The combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for non-motorized street users.

Brief History of Traffic Calming

Traffic calming began in the Netherlands in the 1960s with the design of "Woonerven", or "living yards". The "Woonerven" integrated motor traffic with pedestrian and bicycle traffic on shared street space. In the late 1970s, Germany began working in this area using the term "Verkehrsberuhigung" which would eventually be translated as "traffic calming".

Objectives of Traffic Calming

Traffic calming measures are mainly used to address speeding and high cut-through traffic volumes on neighborhood streets. These issues can create an atmosphere in which non-motorists are intimidated, or even endangered, by motorized traffic. Additionally, high cut-through volumes become an increased concern when larger commercial vehicles are involved. Along with the additional amount of traffic generated within the neighborhood, cut-through motorists are often perceived as driving faster than local motorists. By addressing high speeds and cut-through volumes, traffic calming can increase both the real and perceived safety of pedestrians and bicyclists, and improve the quality of life within the neighborhood.

Education, Enforcement, Engineering

Education: Communities with educational programs seek to remind speeding drivers of the negative effects of their actions, often by stressing that the community's children are the most at risk. Educational campaigns may use brochures or neighborhood newsletters to spread this message. Newsletters may also contain information on speeding fines (particularly in school zones), pedestrian and bicycle safety tips, and information on average speeds in the neighborhood.

Enforcement involves a more intensive police presence and a greater allocation of time to enforcing the speed limit in a particular neighborhood. Unfortunately, it is often not practicable to maintain a police presence at the level needed to permanently lower speeds. However, consistent visible enforcement does lead to respect of the speed limit by motorists.

Engineering includes, but is not limited to, traffic calming measures. It can also include the use of signs and pavement markings to obtain the desired effect.

Prior to installing traffic calming measures on local or collector streets, traffic conditions on adjacent arterial streets should be investigated to determine if operational deficiencies are contributing to the identified traffic concerns. If the adjacent arterial streets are the responsibility of the local government, these deficiencies should be addressed before traffic calming is considered. In addition, when the use of traffic calming measures may divert large volumes of traffic from local streets, the effects on adjacent roadways should be addressed.

Where are Traffic Calming Measures Appropriate?

• Local residential streets
• Collector streets with predominantly residential land uses
• Arterial roads within downtown districts or commercial areas (with posted speeds of 40 mph or less)

Traffic Calming Issues

Funding
Compared to other transportation expenditures for local governments, traffic calming program expenses are rarely significant. Therefore, local governments have some flexibility in determining how to fund their programs. Local governments nationwide most frequently fund their traffic calming programs from capital improvement funds, general funds, or State gas tax subsidies. If the project is low on the priority list, many governments require neighborhood residents to pay for installation and/or maintenance of traffic calming measures and accompanying landscaping.

In Pennsylvania, Liquid Fuels funds may be used for traffic calming measures. However, no money has been designated at the State or Federal level specifically for implementation of traffic calming projects. This means that traffic calming projects must compete with other types of projects, or measures can be included as part of a larger project, if State or Federal dollars are being requested.

Emergency Service Vehicles
Police departments generally have little opposition to (and often endorse) traffic calming measures because of their potential to reduce speeds and crashes. Fire departments may also recognize their benefit for increasing safety. However, emergency service providers may be slowed or inconvenienced by certain types of traffic calming measures. Generally, longer and heavier vehicles must slow to a greater extent than passenger cars to negotiate various measures. For fire trucks, which are longer than normal passenger vehicles and have stiffer suspensions, sudden vertical deflection (speed humps, etc.) can be more jarring and may sometimes lead to discomfort for passengers. Traffic calming measures may have an even greater effect on ambulances that are transporting patients. While many municipalities have successfully implemented traffic calming programs with no resistance from emergency service providers, it is important that they be consulted very closely when any traffic calming program is formulated and projects are identified.

1. Only permit traffic calming measures with minimal or no impacts on emergency response times on major emergency response routes.
2. Alter the design of measures to improve emergency vehicle maneuvering or to allow emergency access.

Landscaping

When landscaping is considered in conjunction with traffic calming measures, the local government may consider recruiting neighborhood volunteers for routine landscape maintenance and litter removal. Without community help, the costs associated with landscaping can sometimes be large. If there are no volunteers (or if volunteers diminish over time), the local government should consider using a low-maintenance landscaping plan.

When deciding what types of landscaping to use for a traffic calming measure, one must always consider sight distance requirements and whether the landscaping will introduce "fixed objects" which may pose a potential hazard if struck by errant vehicles. In certain applications, large trees, rocks, and other similar objects could pose a potential hazard to motorists and pedestrians. In these situations, smaller shrubs and plants that do not pose a safety concern should be considered. Along with the safety concerns of introducing a "fixed object", the landscaping may also become a sight distance problem as the plants mature if they are improperly placed, not maintained, or if the wrong types of plantings are used. For this reason, it is important to consider plant type, growth, and location when landscaping is being considered.

Snow Removal

Many of the traffic calming measures identified in this Handbook may have an effect on the removal of snow and ice. Therefore, measures should be clearly identified and equipment operators made aware of the types of measures that are installed. Doing so will improve the snow removal operation and help prevent damage to the snow removal equipment or the measure itself.

Drainage

The installation of traffic calming measures may change the drainage patterns of the roadways on which they are located. It is very important to review drainage characteristics when determining which measures are most appropriate. Otherwise, problems such as ice/water accumulation on a pedestrian crossing or roadway could occur.

ADA Requirements

Traffic calming measures must be designed to accommodate all people in the community. To accomplish this goal, measures that are implemented to improve pedestrian safety, or have an effect on pedestrian travel, must be designed to meet the requirements set forth in the Americans with Disabilities Act.

Ranking System

To determine how much priority a given traffic situation should be given, you can use the following table to assess priority from 0 to 100.

There may be existing conditions, other than what is included on your project ranking system, that warrant the need for traffic calming. Establishing the ranking for these traffic calming projects will require the use of engineering judgement.

Local Traffic Advisory Committee (LTAC)

The LTAC is a standing committee which coordinates all requests for traffic calming measures made within a local jurisdiction. This committee typically includes a municipal/county engineer, a municipal/county planner, a representative from the governing body, a representative from emergency services, one or more local citizens, and a representative from public works. If the local jurisdiction does not have an LTAC, it is recommended that the local government establish one.

Categories of Traffic-Calming Techniques

• Horizontal Deflection refers to two types of traffic calming measures. The first type hinders the driver's ability to drive in a straight line by creating a horizontal shift in the roadway. This shift forces drivers to slow their vehicles in order to safely navigate the measure. The second type of horizontal deflection measure is designed to narrow the width of the travel lane. Doing so reduces the usable surface of the roadway causing drivers to slow their vehicles to maintain an acceptable level of comfort. Although horizontal deflection measures are mainly used to address speed concerns, applications that narrow the travel lane can improve pedestrian safety by reducing the width of the crossing. Horizontal deflection measures may also have the secondary effect of reducing volumes; however, the effects will typically be minor.
  
  

  Curb extension/bulb-out	Areas of expanded curbing that extend across a parking lane and may narrow a travel lane.
  Chicane	Series of 3 bulb-outs, staggered at mid-block locations on alternating sides of the street.
  Gateway	Entrance treatment, typically using physical and textural changes, that provides identity to an area.
  On-street parking	Provision of on-street parking that reduces roadway width.
  Raised median island / pedestrian refuge	Narrow islands, at mid-block or intersections, between travel lanes with breaks in landscaping and curbing for pedestrians.
  Traffic circle	Raised island in the center of an intersection that requires vehicles to travel counterclockwise around the circle.

• Vertical Deflection refers to traffic calming measures that create a change in the height of the roadway. When designed properly, vehicles must slow down over these measures in order to avoid unpleasant bumping sensations. As with horizontal deflection measures, vertical deflection measures are mainly used to reduce vehicle speeds, with only minor effects on traffic volumes. Vertical deflection measures can also be used to improve the safety of pedestrian crossings.
  
  

  Textured crosswalk	Use of pavers or other materials to demarcate crosswalks and alert motorists that they are entering a pedestrian-friendly area.
  Speed hump	Raised humps in the roadway, typically 3 inches high with a 12 or 22-foot travel length.
  Raised crosswalk	Marked pedestrian crossings elevated 3 to 6 inches above street grade at intersections or mid-block.
  Raised intersection	Intersections, including crosswalks, raised 3 to 6 inches above street grade.

• Physical Obstruction refers to measures that prevent particular vehicle movements, thereby discouraging or eliminating cut-through traffic. The overall traffic volume reduction depends upon the nature of the traffic calming measure and the number of movements obstructed.
  
  

  Semi-diverter	Directional closure created by physically blocking half the street.
  Diagonal diverter	Physical barrier placed diagonally across a four-way intersection to create two unconnected intersections.
  Right-in / right-out island	The use of raised islands to prevent left turns and through movements, to and from side streets, at intersections with major streets.
  Raised median through intersection	Median barrier through an intersection that discourages through traffic in a residential area by restricting movements.
  Street closure	The use of a cul-de-sac to close a roadway by extending a physical barrier across the entire width, obstructing all traffic movements.

• Signs and Pavement Markings can be used as traffic calming measures that regulate traffic movements in lieu of physical changes to the roadway. In certain applications, these measures may produce the same effect as the physical traffic calming measures. However, police enforcement is often required to ensure motorist compliance.

Use of Signs and Pavement Markings for Traffic Calming

Although traffic calming has gained a great deal of attention in recent years, traffic engineers have been implementing measures for the past few decades to reduce cut-through traffic and slow traffic in residential areas. These traditional methods of traffic calming generally involved the use of signing and pavement markings. This type of traffic calming can be inexpensive and it can be installed in a short period of time. For these reasons, signing and pavement markings have been used as a "quick fix" for engineers looking to improve the quality of life in residential areas, improve safety in the vicinity of schools and playgrounds, and protect pedestrians in downtown areas. The following information describes a few of the various types of signing and pavement marking devices that have been used to calm traffic.

Speed Limit Signing: Field investigations of citizen complaints of speeding on residential streets often reveal that very few, if any, speed limit signs are in-place. Although statutory speed limits exist for 25, 35, 55, and 65 mph, only a 55 mph speed limit is enforceable without the posting of speed limit signs. For this reason, residential streets must include speed limit signing if a speed limit other than 55 mph is to be enforceable. The Pennsylvania Vehicle Code (Title 75), §3362 indicates that speed limit signing must be in accordance with Department regulations to include "...posting at the beginning and end of each speed zone and at intervals not greater than one-half mile". In addition, the installation of speed limit signing will function as a constant reminder of the roadway's speed limit.

Multi-Way Stop Signs: A common request made by citizens is to use multi-way stop sign control as a means of slowing traffic. However, multi-way stop sign control should only be installed in accordance with the warrants listed in PennDOT Publication 201. If installed where not warranted:

• Traffic rarely comes to a full stop.
• Motorists increase their speed between stop signs to make up for lost time.
• Residents may gain a false sense of security.

The use of unwarranted stop signs can create disrespect for stop sign control at other locations where it is truly needed.

As the volume disparity increases between opposing traffic flows at an intersection, the stop control is increasingly disobeyed by the motorists on the higher volume street. Unwarranted multi-way stop controls are particularly dangerous where vehicle speeds through the stop sign are greater than 10 mph.

This situation is very common when streets are wide, sight distances are good, and the opposing traffic ratio is greater than 60/40. Typically, regardless of the volumes, most motorists tend to obey stop signs if the traffic split is no greater than a 60/40 ratio.

When implemented after a proper engineering study, multi-way stop control is an excellent tool to reduce right angle crashes. As previously stated, multi-way stop control should not be used for controlling speeds.

Turn Prohibitions are an excellent "quick fix" that can be used for both 24-hour or part-time applications (restrictions that address problems during specific time periods, such as 7:00 AM to 9:00 AM or 4:00 PM to 6:00 PM). One drawback is that the residents living in the area must also abide by the posted restriction. In addition, periodic enforcement is essential to ensure continued compliance with the restriction.

If the cut-through traffic occurs only during certain peak hours, part-time applications should be used. When turn prohibitions are used in this application, supplemental signing indicating the restricted hours when the prohibition is in-place must be included.

One-Way Streets: Since turn restrictions are only spot controls, they may be violated with some frequency by motorists in the absence of police enforcement. A more effective control may be to create a one-way street. One-way streets are often implemented in parallel pairs to ensure a good circulation pattern.

One-way streets should only be implemented after careful evaluation. This type of measure is far more restrictive to the residents living on the street than a turn prohibition. In addition to their restrictive nature, speeds tend to increase on one-way streets due to fewer conflicts and a wider travel lane. If this occurs, additional traffic calming efforts may be needed.

Roadway Narrowing with Edge Lines: Many residential streets have been constructed to such a width that getting motorists to obey a 25 or 30 mph posting is extremely difficult. In addition, it can be costly to physically narrow the roadway or install various physical traffic calming measures. A low-cost way of reducing speeds is to narrow the roadway lane through the use of edge lines and centerlines. A number of jurisdictions across the country have installed this type of pavement marking application to create 9 to 10-foot-wide lanes. These applications have generally reduced speeds by 1 to 2 mph with reported reductions as high as 5 mph in some locations. This pavement marking application is appropriate on local streets and low-volume minor collectors, but should not be used on major collector or arterial streets.

Transverse Markings: Double thick thermoplastic transverse pavement markings have been successful in slowing traffic in diverse areas such as school zones, hospitals, approaches to severe curves, and stop signs. These markings typically consist of five transverse, 6-inch-wide stripes, installed 2 feet on center, repeated every 100 feet. Depending on conditions, three to five sets of clusters are installed per approach. It is estimated that each cluster reduces approach speeds by 1 to 3 mph. As vehicles travel over these thermoplastic markings the noise and vibration alerts the driver. Because of the noise they generate, it may be inappropriate to use this application in locations with nearby residents.

Source: Pennsylvania's Traffic Calming Handbook [large pdf], PennDOT publication No. 383 January 2001

Recommended Websites

• Active Living by Design is a national program of the Robert Wood Johnson Foundation established to evaluate innovative approaches to increase physical activity through community design, public policies, and communications strategies.
• The American Public Transportation Association is a Washington-based advocacy organization that leads the way in increasing, expanding, and strengthening the role of public transportation.
• The Center for Community Change is committed to strengthening low-income communities through a diverse range of programs. The center's Transportation Equity program addresses the issues related to movement and people.
• The Community Transportation Association of America has been bringing together community members to identify mobility challenges and design transit solutions since 1989. The organization is founded upon a vision of the future of transportation based on the fundamental American values of freedom, independence, dignity, and choice.
• The National Center for Bicycling and Walking is the major program of the Bicycle Federation of America, a national nonprofit corporation established in 1977. The center's mission is to create bicycle-friendly and walkable communities.
• The Project for Public Spaces is a nonprofit organization dedicated to creating and sustaining public places that build communities, providing technical assistance, education, and research.
• Safe Routes to School
• The Surface Transportation Policy Project
• The Victoria Transport Policy Institute

Recommended websites from Moblility Friendly Design Standards [pdf]