WRI Low-Speed Zone Guide - Guidance on how agencies can plan, design, and implement effective low-speed zones from the World Resources Institute. This guide includes information on bringing low-speed zone designs together to fit the context as well as operating and evaluating a low-speed zones.
NACTO City Limits Guide - This guidance provides practitioners a detailed, context-sensitive method to set safe speed limits on urban streets and includes a checklist guide setting context sensitive and safe speeds based on certain conditions and presence of all road users.
Traffic Calming - combination of physical measures to reduce the effects of motorist behaviors and improve conditions for all street users.
Self-enforcing road - a road that encourages drivers to select operating speeds consistent with the posted speed limit.
While there are at least 4 Es for safety in the transportation profession, the first 3 Es—engineering, enforcement, and education—are critical to transportation professionals looking to reduce speeds and implement a speed management program.
Transportation professionals can implement engineering strategies and countermeasures, often referred to as traffic calming, to reduce speeds on a road with higher than desired speeds. Engineering strategies and countermeasures can also be used more broadly, to change a road behavior in order to create a safer condition. A strategy is a policy or plan to heighten awareness of speed, road context, multiple road users or other safety element that may impact traveling at the safest speed. A countermeasure is an intentional alteration to the road or surrounding environment that changes the behavior of road users. The Federal Highway Administration (FHWA) Traffic Calming Eprimer module and the National Association of City Transportation Officials (NACTO) Urban Street Design Guide and Urban Bikeway Design Guide are resources related to traffic calming for transportation professionals. Additionally, NACTO also recently released a City Limits: Setting Safe Speed Limits on Urban Streets Guide that provides practitioners a detailed, context-sensitive method to set safe speed limits on urban streets. NACTO's City Limits includes a checklist to guide setting context sensitive and safe speeds based on certain conditions and presence of all road users.
When selecting an engineering strategy and/or countermeasure, transportation professionals should consider road environment, type and classification, users, crash history, cost, and effectiveness to determine the most appropriate method of traffic calming and speed reduction.
Engineering strategies are usually comprehensive plans to re-design a road and surrounding area to change a road condition to provide a safer environment all road users. The following speed management strategies may be considered to raise awareness for safe speeds in predominantly denser land use settings:
Context Sensitive Solutions - are driven by a collaborative, interdisciplinary design process that involves all stakeholders, including citizens, to develop a road facility that fits the physical setting and the needs of the public. Context sensitive design involves accommodating all street users, making decisions that reflect a shared stakeholder vision, and demonstrating an understanding of the tradeoffs that come with balancing multiple needs on, typically, complex urban roads. The ITE Implementing Context Sensitive Design on Multimodal Corridors: A Practicioner's Handbook, Designing Walkable Urban Thoroughfares: A Context Sensitive Approach and FHWA Context Sensitive Solutions and Design are helpful resources for transportation professionals considering a context sensitive solutions related to speeding and safety. The World Resources Institute (WRI) Low-Speed Zone Guide presents strategies for planning, designing, building, and evaluating low-speed zones in cities in the U.S. and internationally.
Complete and Shared Streets – Complete are roads designed for use by all modes of transportation and shared streets are roads where all users are given equal priority by minimizing the segregation between modes of transportation. Roads have predominately been designed giving priority to motor vehicles, but now roads, especially urban streets, are being re-designed to incorporate safe paths of travel for all road users, from pedestrians to bicyclists. The type of street, the context and diversity of users determine whether a complete street or a shared street are the safest strategy for a road. Providing facilities for all road users reduces congestion by motorists and creates a safer environment for all road users. The Smart Growth America National Complete Streets Coalition provides resources for transportation professionals on completes streets, including the Safe Streets Academy and the Dangerous by Design reports. Additionally, the American Planning Association report Complete Streets: Best Policy and Implementation Practices and the FHWA guide Achieving Multimodal Networks Applying Design Flexibility & Reducing Conflicts are helpful resources when implementing complete streets.
Self-enforcing Roadways - The application of self-enforcing roadways is one possible approach to manage speeds. It encourages driver speed choice that is compliant with the regulatory speed limit. The FHWA report Self-Enforcing Roadways: A Guidance Report published in January 2018, describes six self-enforcing road concepts that may be used to design roadways that produce operating speeds consistent with the desired operating speeds of the roadway.
Engineering countermeasures are used on an existing road to change undesirable behaviors, such as reducing speeds and/or congestion on a road or road network. Traffic calming is a physical alternation implemented either based on engineering strategies or when speed is identified as a problem. Speed management countermeasures consist of horizontal, vertical, lane narrowing, roadside, and other features that use physical or psycho-perception means to produce desired effects. Traffic calming measures can be categorized into the following categories:
Horizontal deflection hinders the ability of a motorist to drive in a straight line by creating a horizontal shift in the roadway. This shift forces a motorist to slow the vehicle in order to comfortably navigate the measure. Examples of types of horizontal deflections are features are lateral shifts, chicanes, roundabouts, etc.
Vertical deflection creates a change in the height of the roadway that forces a motorist to slow down in order to maintain an acceptable level of comfort. Examples of types of vertical deflection are features such as speed humps, cushions, tables, raised crosswalks, etc.
Street width reduction narrows the width of a vehicle travel lane. As a result, a motorist slows the vehicle in order to maintain an acceptable level of comfort and safety. The measure can also reduce the distance a pedestrian walks to cross a street, reducing exposure to pedestrian/vehicle conflicts. Examples of types of street width reduction are features such as road diets, corner extensions, medians or pedestrian refuge islands, on-street parking, etc.
Other countermeasures may not fit into any of the above categories but are often awareness mechanisms to reduce speeds, including, but not limited to speed feedback signs, high visibility pavement markings, enhanced curve delineation, stoplight reflective borders, etc.
Most often, multiple engineering countermeasures are installed to create a truly safe road for all users, often referred to as a self-enforcing road. The FHWA Engineering Speed Management Countermeasures: A Desktop Reference of Potential Effectiveness in Reducing Speed outlines engineering countermeasures appropriate for implementation based on road type, volume, speed, and safety concern. The ITE Traffic Calming website outlines all types of engineering countermeasures available to reduce speeds. The FWHA document Making Our Roads Safer One Countermeasure at a Time, 20 Proven Safety Countermeasures that offer significant and measurable impacts to improving safety is very helpful in providing basic design guidance and statistical information on the safety benefit of each engineering countermeasure. The FHWA Road Diet Informational Guide and Pedestrian and Bicycle Safety Guide and Countermeasure Selection System, the National Highway Traffic Safety Administration (NHTSA) Countermeasures That Work: A Highway Safety Countermeasure Guide For State Highway Safety Offices and the iRAP Road Safety Toolkit also provide guidance on traffic calming.
Enforcement is critical to achieving a safe use of roads, compliance with speed limits, and ensuring overall movement at a safe speed. According to NHTSA, more than half of all traffic stops result from speeding violations. Transportation professionals assist enforcement authorities to ensure speed enforcement is fair, rational, and motivated by safety concerns.
Traditional enforcement involves patrol officers monitoring where crashes related to speeding have occurred and/or where violations of the speed limit occur. To be effective over the long term, traditional enforcement measures need to be consistent, sustained, and must provide data back to transportation professionals to assist in evaluation of road designs. Transportation professionals should remain involved in traditional enforcement to monitor proper posting of signs and other elements of maintaining a speed management program.
Enforcement of speed limits can also be accomplished through the use of automated speed cameras that record a vehicle speed using radar and a camera that captures the vehicle when the threshold speed is exceeded. Violation evidence is processed and reviewed in an office environment and violation notices are delivered to the registered owners of identified vehicles after the alleged violation occurs. Transportation professionals should be involved in determining the location and type of automated speed enforcement with law enforcement professionals. Fixed ASE units are permanently mounted in fixed locations, in areas such as school zones; semi-fixed and mobile ASE units are mounted to housing, a vehicle or trailer to allow for mobile enforcement as needed, such as in construction zones; and speed-on-green ASE units are typically used to detect red light violations but can also detect speed violations through intersections.
Automated speed enforcement allows for a high rate of violation detection, increases safety of first responders, and ensures consistent enforcement of speeds. However, automated speed enforcement delays violation and penalty, is limited in the range of enforcement, and may limit the ability to educate offenders. Automatic speed enforcement should be used to solve a safety problem where engineering measures cannot be installed to calm traffic. Often, state laws determine the use of automatic speed enforcement and limits local implementation.
The NHTSA Speed Enforcement Camera System Operational Guidelines provides guideance on ASE operations. The Insurance Institute for Highway Safety (IIHS) Highway Loss Data Institute tracks state laws on automated speed enforcement and also provides other resources related to ASE. The National Transportation Safety Board (NTSB) Reducing Speeding-Related Crashes Involving Passenger Vehicles, the NHTSA System Analysis of Automated Speed Enforcement Implementation and the Pedestrian and Bicycle Information Center An Overview of Automated Enforcement Systems and Their Potential for Improving Pedestrian and Bicyclist Safety are also helpful resources on automatic speed enforcement.
IIHS has also conducted research into Intelligent Speed Assistance (ISA) and provides information on how ISA technology is being explored to encourage safer vehicle speeds. The European Union recently passed legislation requiring Intelligent Speed Assistance in all new car by 2022.
The NHTSA Highway Safety Program Guideline on Speed Management suggests the following actions for education and communication: