In one implementation, sets of probe data are collected by probe vehicles. The probe data describes the driving characteristics of the probe vehicles. The sets of probe data are sent to a server or a mobile device for analysis. A polycurve, including a piecewise function of map data, is modified based on the probe data. The polycurve may be a spline curve for an advanced driver assistance system. The modified polycurve may be used in the advanced driver assistance system for a vehicle traveling along the same path previously traversed by the probe vehicles. Based on the polycurve modified by the probe data, a driver assistance feature is provided to the vehicle.