El National Highway Cooperative Research Program (NCHRP) ha lanzado una convocatoria de análisis para determinar los efectos de los elementos viales, laterales y no viales en las velocidades de operación en las carreteras con un límite de velocidad de entre 30 y 40 mph, y para desarrollar recomendaciones sobre cómo pueden incorporarse los hallazgos en el proceso de diseño de la carretera.
The American Association of State Highway and Transportation Officials (AASHTO) defines design speed as “a selected speed used to determine the various geometric features of the roadway. The assumed design speed should be a logical one with respect to the topography, anticipated operating speed, the adjacent land use, and the functional classification of the highway.” The working definition for “target speed” is the operating speed that the designer intends for drivers to use. The topic of “design speed” versus “target speed” typically focuses on low-speed urban and suburban roadways, especially where the 85th percentile speed is higher than the posted speed limit. Research is needed to gain a better understanding of how roadway, roadside, and non-roadway elements influence the operating speed—the actual speed of the driver—in order to improve roadway designs and reliably achieve desired speed outcomes.
The objectives of this research are to (1) determine the effects of roadway, roadside, and non-roadway elements on operating speeds on roadways with a target speed between 30 and 40 mph and (2) develop recommendations on how the findings can be incorporated into the roadway design process.
Accomplishment of the project objectives will require careful consideration of and adherence to the research plan.
The NCHRP is seeking the insights of proposers on how best to achieve the research objectives. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers’ current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objectives. Task descriptions are intended to provide a framework for conducting the research.
Consideration shall be given to at least the following concepts and questions:
- What are the quantifiable impacts of elements or combination of various elements on operating speed (e.g., roadway and lane width, shoulder width, curb height and shape, roadway alignment, innovative intersection treatments, driveways, trees, on-street parking, street lights, bicycle facilities, transit stops, signal density, sidewalks and street furniture, building setback, land use, and pedestrian and bicyclist activity)?
- How do these impacts or elements vary for different types of roadways, including those with differing geographic distribution, roadway types, driving conditions, context classifications, functional classifications, and in particular those with multimodal users?
- Implications for traffic operations [Highway Capacity Manual (HCM)] and safety performance [Highway Safety Manual (HSM)].
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