Speed Prediction for Two-Lane Rural Highways

2000PDFTech Reporthttps://www.fhwa.dot.gov/publications/research/safety/ihsdm/99171/99171.pdfhttps://www.fhwa.dot.gov/publications/research/safety/ihsdm/99171/FHWA-RD-99-171DTFH61-95-R-00084Design speedTwo lane highwaysRural highwaysRural roads--United States--Design and construction--EvaluationSpeed limits--United States--EvaluationUnited StatesUnited States. Federal Highway AdministrationFitzpatrick, Kay; Elefteriadou, Lily; Harwood, Douglas W.; Collins, Jon M.; McFadden, John; Anderson, Ingrid B.; Krammes, Raymond A.; Irizarry, Nelson; Parma, Kelly D.; Bauer, Karin M.; Passetti, KarlUnited States. Federal Highway Administration. Office of Safety Research and Development; Texas Transportation Institute; Turner-Fairbank Highway Research CenterFederal Highway AdministrationDesign consistency refers to the conformance of a highway\u2019s geometry to driver expectancy. Drivers make fewer errors in the vicinity of geometric features that conform to their expectations. A technique to evaluate the consistency of a design is to evaluate changes in operating speeds along an alignment. To use operating speed as a consistency tool requires the ability to accurately predict speeds as a function of the roadway geometry. In this research project, several efforts were undertaken to predict operating speed for different conditions such as on horizontal, vertical, and combined curves; on tangent sections using alignment indices; on grades using the TWOPAS model; and prior to or after a horizontal curve. The findings from the different efforts were incorporated into a speed-profile model. The model can be used to evaluate the design consistency of the roadway or can be used to develop a speed profile for an alignment. The model considers both horizontal and vertical curvature and the acceleration or deceleration behavior as a vehicle moves from one feature to another.79