1. A system for communicating data to a vehicle control system, comprising: a vehicle bus provided within a vehicle and operable to provide message-based communication to a set of control systems for the vehicle; a server-side module, communicatively coupled to the vehicle bus, operable to: acquire path-preview data indexed to values of a metric for vehicle progress; perform regression analysis on the path-preview data to generate a set of coefficients assigned to sub-functions combined in an approximation function characterizing variation in the path-preview data relative to the values indexed; transmit the coefficients by messaging on the vehicle bus; a client-side module, communicatively coupled to the vehicle bus, operable to: receive the messaging from the vehicle bus; extract the set of coefficients from the messaging; evaluate the approximation function at the client-side module by applying the set of coefficients to a copy of the sub-functions maintained at the client-side module; utilize an evaluation of the approximation function to direct a control system.