ABSTRACT The megatrends “reduction of emissions” and “fuel consumption reduction” play a predominant role in the development of powertrains. For transit buses this implies both the reduction of emissions and pollutions of the internal combustion engine, and, on the other hand, a further reduction of noise and brake dust. Also very important is the reduction of both fuel consumption and CO2 emissions. For all these targets the actual developments on the engine side have led to great improvements in the last decades, but what can be mentioned for the other components of the powertrain, especially looking for transmissions? First of all the relevant trends for transit buses have to be considered: A large increase of the torque of the combustion engines during the last years has a big impact on the development of transmissions for buses. Furthermore, due to the higher coolant temperatures of the engine's cooling systems to perceive a better emission behaviour because of a better efficiency of the combustion engine, coolant systems for the transmissions have to be improved as well. For transit buses in established markets powershift automatics have a share of more than 90%. The presentation will give the most recent developments for both hardware- and function related parts of the transmissions. The function and software parts demonstratethe increasing influence of electronics and their interactions within the vehicle's electronic architecture. All the different vehicle electronics are driven collaborative to achieve best suited solutions for the different areas of customer's requests. The development of modern powershift transmissions today means also an intensive use of simulation tools for all fields. This exceeds by far the former strength, fatigue and vibration analyses. Practical examples, also including manufacturing simulation, will show the relevance of simulation to the development process. All the simulation results lead to a reduction of development time and a better product quality and accuracy. The presentation ends with an evaluation of different hybrid solutions. Here for the future systems are needed which combine both fuel consumption reduction and improved life cycle costs. ZF with its parallel hybrid system will offer a very attractive solution for the market. INTRODUCTION With the new EcoLife powershift transmission, ZF Friedrichshafen AG has developed a city bus transmission with a three-stage planetary gear set that is already designed for future operating conditions. The objective of the development was clear: low operational costs, lots of power. With the transmission software TopoDyn Life, the transmission is in an optimal operation mode throughout the entire route. MARKET REQUIREMENTS The demands on modern city buses are steadily increasing. For one thing, the legal side must be taken into consideration: ZF EcoLife - The latest Generation of Powershift Automatics for Transit Buses2011-01-1423 Published 04/12/2011 Joachim Foth ZF Copyright © 2011 SAE International doi:10.4271/2011-01-1423Downloaded from SAE International by Univ of California Berkeley, Monday, August 06, 2018regulations regarding CO 2 emissions, noise development and safety requirements obligate not only the vehicle manufacturers, but also the suppliers of important components and systems. This places special significance on the driveline. In addition, economic aspects play an increasingly important role. A comparatively low reduction in fuel consumption per vehicle is already an important cost factor for transport services and fleet operators. That kind of savings can ensure your own long-term competitiveness. The same applies for longer maintenance intervals, which help reduce the lifelong operating costs of a bus, or the life-cycle costs (LCC). And of course comfort demands for passengers and driver must also be considered. Many passengers are not necessarily dependent on public transportation and can choose between the city bus and t