An Estimate Method for Accuracy of Fitting Horizontal Alignment in Old-Highway Based on Fitting Normal Error

After discussion about definition and constitution and properties of fitting normal error, one new method is put forward, that suggests the fitting normal error represents the error of fitting the horizontal alignment in old:highway. In addition, the accuracy indexes of fitting horizontal alignment in old:highway based on fitting normal error is established. The algorithms of swinging approach on compressible size step can be used to calculate the fitting normal error. From the way and basic norm of decision about fitting normal error’ sign discussed, It is practicable that the quantity of fitting the horizontal alignment in old:highway is controlled by the accuracy index of fitting the horizontal alignment in field and interior work. Finally, an example of estimate for accuracy of fitting horizontal alignment in reform design of the State Highway G321 is offered.