This work considers the problem of robustly controlling systems that have an implicit parametric coupling, and specifically considers the problem of lateral control of passenger vehicles at highway speeds. Passenger vehicles collectively have a wide range in dynamic behaviors mainly due to the ranges in size between different models. However, as vehicle size increases, the length, mass and mass moments of inertia also increase in predictable relationships that strongly couple these parameters to each other. The proposed control technique exploits this inherent parametric coupling in order to design a single robust controller that can be easily adapted parametrically from vehicle to vehicle. Parameter decoupling in the design model is achieved in the control synthesis step using a dimensional transformation. The resulting design model presents a system representation suitable for robust control of a very wide range of passenger vehicles using only a dimensional rescaling. This method is distinguished from prior work in that the structure of parametric dependence is included in the controller synthesis. The resulting design is tested on a scaled vehicle test setup developed at Pennsylvania State University. Both simulation and experimental results have shown the effectiveness of the technique for the proposed application.