Abstract
Design consistency refers to the condition whereby roadway geometry does not violate driver expectations. As such, most evaluations of highway geometric design consistency are based on operating speed profile analysis, which relates safety with speed variability. This paper presents a new operating speed model in which the operating speed depends on curve radius. The model uses car speeds collected for 42 curves on two-lane rural highways in Southwest Spain. A comparison between this model and several models developed previously in other European countries has been made. This comparison emphasizes the influence of the model chosen on the results obtained. In addition, the incorporation of laser, GPS and GIS for vehicle speed measurement in the inexpensive yet reliable manner is discussed.
Highlights
Design consistency refers to the condition in which roadway geometry does not violate driver expectations
In this paper the design of a data-storage system which, in addition to vehicle speeds, records their distance and speed sign and allows the location where the measurements were made to be recorded is discussed. This system consists of a laser, a low-cost Global Positioning System (GPS; SIRF III type) receiver and a hand-held computer
The use of GPS allows determining the coordinates of the points where speed measurements are taken
Summary
Design consistency refers to the condition in which roadway geometry does not violate driver expectations. Dell’Acqua and Russo (2011) have proposed two models for operating speeds on horizontal curves: one for horizontal curves with a mean CCR of less than 240 gon/km (51 curves, R2 = 0.81) that uses the variables CCR, width of travel lanes plus shoulders, length of single circular curve, number of residential driveways per kilometre, length of preceding tangent, intersection distance indicator and pavement distress indicator, and another for horizontal curves with a mean CCR of more than 240 gon/km (43 curves, R2 = 0.72) that uses the variables CCR, width of travel lanes plus shoulders, length of single circular curve, number of residential driveways per kilometre, radius of preceding curve, and pavement distress indicator In their extended model, Lamm and Choueiri (1987) use traffic (Annual Average Daily Traffic – AADT, vpd (vehicles per day)) as one of the variables, whereas various other authors take into account the speed in the approach tangent (McFadden, Elefteriadou 1997). This paper presents a combination of laser, GPS and GIS for vehicle speed measurements
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