A processor operatively coupled to a speed sensor adapted to generate a
measure of a longitudinal speed of a vehicle on a roadway, and to a
source of a measure of yaw rate of the vehicle, provides for selecting a
most likely roadway model of a plurality of different roadway models and
for outputting a corresponding associated at least one curvature
parameter as an estimate of curvature of the roadway, wherein the
processor incorporates a plurality of curvature estimators associated
with the corresponding plurality of different roadway models.