Automotive industry has been integrating growing number of buses and electrical control units (ECU) into the vehicle to cope with the stringent emission and fuel consumption regulations, and to improve driving safety and comfort. The fast evolving electronics hardware and software technologies complicate the system design effort even further. To cope with trend in integrating complex embedded software into modern vehicles, we propose an UML-based automotive system object (ASO) software environment to support the vehicle system integrator in developing their vehicle electronics system. To the specific ECU provider, ASO environment provides the vehicle system model as a whole with constituent models to support the ECU designer in assessing ECU collaboration with other components of the vehicle.