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Layout is one of the most important missions of the surveying engineer, which aims to carry out the designed horizontal and vertical geometries of an engineering structure by satisfying the required accuracies. It is necessary to satisfy the required accuracies through the "achieved point standard deviation" which is defined by the product of the errors derived from known point coordinates and the layout measurements. In order to satisfy the required accuracy, the achieved accuracy should be smaller than the required one. The mission of the surveying engineer is planning the layout process by taking into consideration the required and the achieved standard deviations. In this paper, the planning process concerning the measurement error components is explained. The issues regarding the network design, the measurements, and the selection of the proper instruments for the layout are explained to make optimal decisions. The given decision making methods in this study are rather valuable in the special applications which require high accuracy.

A new transition curve-3 (NTC-3), joining two straight lines by providing second-degree contact related to the properties of vehicle–road system without the necessity of a circular arc, is presented. The NTC-3 is offered by curvature and superelevation functions and is compared with the new generation transition curves-1 and -2 (NTC-1, NTC-2) and spiral curves. The properties of vehicle–road system, represented by function of lateral change of acceleration (LCA), are examined for these curves. Three criteria are taken into account to compare the curves. The NTC-3 and NTC-1 are compared in five-different motion models: model with constant velocity, model with positive acceleration, model with negative acceleration, model with negative acceleration – positive acceleration, and model with positive acceleration – negative acceleration. Examination of three criteria shows that NTC-3 is superior to the other curves on the basis of vehicle–road system.Key words: route design, transition curve, vehicle–road system, curvature, lateral change of acceleration, superelevation, motion model.

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