CSS and Safety

CSS and Safety
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What makes a road safe? The issue of safety for all users is a fundamental goal inextricably related to all other CSS design controls and criteria.

Safety for Motor Vehicles
  "It is not uncommon to have a road that is nominally safe (i.e., all of its geometric features meet design criteria) but substantially unsafe (i.e., there is a known or demonstrated high crash problem.)"
Pedestrian and Bicycle Safety
The call for more walkable, livable, and accessible communities, has seen bicycling and walking emerge as an 'indicator species' for the health and well-being of a community. People want to live and work in places where they can safely and conveniently walk and/or bicycle and not always have to deal with worsening traffic congestion, road rage and the fight for a parking space.
Safety for Transit Riders
  "While the safety record of transit bus operations, in general, has been very good, accidents do occur. The resulting injuries, fatalities and property damage often result in expenditure of scarce resources."
Article Icon Article / Paper / Report Nominal and Substantive Safety - CSS Quick Facts
Highway engineers and stakeholders can improve the quality of analysis and discourse through better understanding of what constitutes a “safe” design or decision. First, the subject of safety should always be addressed carefully. There is no such thing as perfectly “safe” highway; one should never promise this nor characterize safety in absolute terms. Second, properly understood, highway safety has been described as having two dimensions, nominal safety and substantive safety.
  • Nominal safety refers to adherence to design practices, standards, warrants, etc.
  • Substantive safety refers to actual (or expected) performance as defined by the frequency and severity of crashes.

Article Icon Article / Paper / Report Synthesis of Safety Research Related to Speed and Speed Management
"This report presents a synthesis of research findings on the safety effects of speed, speed limits, enforcement, and engineering measures to manage speed. The report updates a similar synthesis published in 1982. A great deal of speed related research has been carried out since that time. This synthesis highlights the results of significant safety research related to speed completed since the last update. Some of the earlier benchmark studies are incorporated where appropriate."
--  National Highway Traffic Safety Administration
Federal Highway Administration

Book Icon Book Traffic Calming: The Solution to Urban Traffic and a New Vision for Neighborhood Livability
"Traffic Calming is a holistic, integrated approach based on common sense which seeks to maximize mobility while creating a more livable city by reducing the undesirable side effects of that mobility. One definition of traffic calming is 'environmentally compatible mobility management.'"
-- Citizens Advocating Responsible Transportation (CART)
Article Icon Traffic Fatalities and Injuries: The effect of Changes in Infrastructure and Other Trends
"...Changes in highway infrastructure that have occurred [in the U.S.] between 1984 and 1997 have not reduced traffic fatalities and injuries and have even had the effect of increasing total fatalities and injuries ... Other factors, primarily changes in the demographic age mix of the population, increased seat-belt usage, reduced per capita alcohol consumption, and improvements in medical technology are responsible for the downward trend in total fatal accidents."
-- Robert B. Noland
Article Icon Article / Paper / Report NCHRP REPORT 500: Guidance for Implementation of the AASHTO Strategic Highway Safety Plan
In 1998, AASHTO approved its Strategic Highway Safety Plan, which was developed by the AASHTO Standing Committee for Highway Traffic Safety with the assistance of the Federal Highway Administration, the National Highway Traffic Safety Administration, and the Transportation Research Board Committee on Transportation Safety Management. The plan includes strategies in 22 key emphasis areas that affect highway safety. Each of the emphasis areas includes strategies and an outline of what is needed to implement each strategy.
--  American Association of State Highway and Transportation Officals
Odense Town Center, Denmark
"In connection with Odense's 1000th years' anniversary in 1988 a number of new developments were inaugurated in the town centre: pedestrian streets, a bus street, and a bicycle route network. This has given the already lively town centre a significant lift, has stimulated the activity in the area, and has markedly improved the visual environment."
Merritt Parkway: Greenwich, Connecticut
Greenwich, CT
Much has been written and reported about the safety improvements and landscape restoration of the Merritt Parkway which started in the 1990s in Greenwich, Connecticut, a unique community that shaped the approach that was ultimately taken to improve this roadway. The community's influence started long before any formal design process was undertaken, and in fact, and was instrumental in motivating the context sensitive design approach (although not called such at the time). Overall this project can be considered an excellent example of how a road represents so much more to a community than simply a transportation conduit. The future of this roadway was community driven and while the DOT provided the leadership and expertise to accomplish the improvements, their use of other professionals, such as landscape architects and historians, improved the final result. This case study focuses on the initial context sensitive design process which preceded the first improvements to the highway and revitalization of the setting.
Merritt Parkway Gateway Project
Greenwich, CT
Since its opening in 1940, the Merritt Parkway has been recognized not only as an essential component of Connecticut's transportation system but as an asset with unique design features and scenic character. During the 1990s, ConnDOT sought to improve the Parkway's safety and operational efficiency while preserving the road's unique characteristics. This case study illustrates this project and the importance of framework development, being flexible in the use of design criteria, and addressing safety problems with specific actions.

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