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In particular on heavy duty commercial vehicles, the continuous braking systems “engine braking system” and “retarder”, which are independent of the service braking system, are installed to handle the continuous braking load on downhill stretches. These systems are also used to reduce lining wear and thermal loads of the service braking system. Exhaust braking systems are the most widely used form of engine braking systems. The current state-of-the-art in retarders is represented by two basic concepts, the electrodynamic retarder and the hydrodynamic retarder. A performance comparison of the different systems shows that low mountain descending speeds are the domain of engine braking systems, whereas retarders are more effective for medium and high descending speeds. The electrodynamic retarder is more favourable for lower road speeds, while the hydrodynamic retarder develops its effectiveness during higher downhill speeds.

The settings of adaptive suspension elements may be switched from a comfortable “soft” characteristic to a safe and “firm” characteristic. Thus the possibility is given to not only improve the ride comfort, but the dynamic driving behavior as well, since no compromise must be made between these two criteria when tuning the suspensions. Such systems seem to be very promising for commercial vehicles, as - because of their changing loading conditions - it is very difficult to design an optimal suspension system using conventional springs and dampers. This paper describes the influence of shock absorbers and air springs with variable characteristics on the ride comfort and the dynamic behavior of a 15-t-truck by investigations done with a simulation system. A series production vehicle without adaptive suspension elements serves as basis. At first the results of measurements and simulations are compared and show a very good concurrence.

Economical and technical aspects justify intelligent suspension systems in commercial vehicles. The tasks of suspensions of vehicles are contradictionary and the prevailing problems cannot be readily solved with conventional suspension systems in a satisfying manner. However, advantages are acquired by the use of adaptive suspension systems. Varying the properties and characteristics of suspension systems in respect to the different loads transported by a commercial vehicle, to vehicle speeds and to dynamic maneuvers, nearly present as good results as closed loop controlled adaptive suspension systems do. For economical reasons fully active suspension systems are only installed in commercial vehicles performing special tasks and services. Partially active suspension systems reduce power consumption and demonstrate satisfactory efficiency.

The consequent means towards improved enhancement of the safety of commercial vehicles will in future times require more and more electronic intelligence, in case a distinct optimization of the systems will not be possible with conventional means. In forefront, endeavours are aimed at the improvements of the functions of the system in regard to driving safety, as well as driver stress relief at lowest possible costs, in order to increase the total cost effectiveness of commercial vehicles. Starting with currently implemented electronic systems up to systems now under development, a continuous development of standalone electronics up to integrated electronic compounding is the current trend. This trend shows advantages of reduced wiring and the number of sensors while it increases the function at the same time.

The simulation of the driving performance of motor vehicles offers the possibility of analyzing the behavior of new commercial vehicles or new systems to be integrated into the vehicle, already before the stage of the first prototypes. Thus, simulation technology may contribute to shorten the time and costs needed for the development of new vehicles and new vehicle systems. As an example, this contribution describes the simulation of a commercial vehicle with adaptive suspension elements. The simulations were used to coarse-tune the suspension elements before installation and fine-tuning them in a prototype vehicle, and to define and optimize the control strategies of electronically controlled suspension systems. A comparison between the costs of the simulation and estimated costs of corresponding field tests substantiates the economical benefits of the simulation.