Tübingen: Boosting environmental performance of full hybrid buses



Sierre (Switzerland)

Challenge area:

Pollution Reduction

Implementation period:


The Challenge

Noise pollution from vehicles remains a major environmental health problem in Europe. Full electrification will significantly reduce these emissions. However, transition towards 100% electromobility will be a gradual process due to several challenges such as adequate availability of charging infrastructure. Therefore, in the years to come the will be other bus technologies still being purchased. Today, from societal and environmental perspective full hybrid technology offers second-best choice offering benefits of partial electrification without operating constraints. One unique aspect of full hybrid technology applied to public transport (PT) is that buses operate on fixed routes. This creates new possibilities to optimise full hybrid buses via the emerging technologies. Specifically, geofencing technology combined with connectivity and data analysis of operating conditions allows to increase electric distance share travelled by full hybrid buses and to turn them into true part-time electric vehicles. It allows to achieve the following goals:

  • Reduction of GHG emissions and energy consumption (environmental goal).
  • Targeted noise emission reduction from full hybrid buses (citizen oriented goal).

Targeted noise reduction means focusing on noise-sensitive areas such as bus stops, narrow streets surrounded by building, etc. The indirect benefit of noise reduction is increased attractiveness of public transport (operated by full hybrid driveline technology).

The Solution

The solution improves environmental and societal performance of full hybrid buses by extending their default electric behaviour with zero emission zones that enable the bus to be electric in additional locations. Key elements of the solution are:

  • Euro VI Volvo full hybrid bus (solo and articulated)
  • Geofencing technology,
  • Connectivity between bus and offboard control,
  • Data analysis of operating conditions detecting optimal locations of zero emission zones

The solution was firstly prototyped in Luxembourg in public transport lines operated by Sales-Lentz. The first large-scale test was carried out in Sierre, Switzerland, where all city routes operated by hybrid were optimised via zero emission zones.

The solution can be deployed in different ways. The most common one is that route analysis is carried out by electromobility specialist from bus provider to determine optimal locations for the zones. The possible locations are determined by energy recovery profile on a given route. There is however certain flexibility in choosing where to implement the zones. This is when the voice of the operator can be taken into account (e.g. the operator can communicate prioritised locations).