1. A method for determining roadway curvature in a vehicle system on a vehicle, said method comprising: determining a range of interest for determining the roadway curvature; collecting shape points from a map database on the vehicle from a current position of the vehicle to an end of the range of interest that define the location of the roadway, where the shape points are defined by World Geodetic System 84 (WGS84) coordinates; converting the shape points from the WGS84 coordinates to Universal Transverse Mercator (UTM) coordinates; fitting a single set of polynomial equations to define a roadway curve using the converted shape points; determining that the single set of polynomial equations exceeds a predetermined curvature accuracy threshold; fitting multiple sets of polynomial equations to multiple roadway segments over the range of interest using the converted shape points; and determining the roadway curvature at a roadway location using solutions to the multiple sets of polynomial equations.