Location: Poland

Date of publication:

Focus Areas: Vehicles.Avoid., Vehicles.Extend., Vehicles.Transform.

Conversion of Diesel Buses into Trolleybuses

Gdynia, Poland, has a long-standing tradition of operating trolleybuses as part of its sustainable urban transport network. However, in the early 2000s, a significant portion of its trolleybus fleet was high-floor and outdated, while the cost of purchasing new low-floor trolleybuses remained prohibitively high. The city sought an innovative, cost-effective, and environmentally responsible alternative: the conversion of used diesel buses into trolleybuses.

The main objectives of this initiative included:

  • Extending the lifecycle of existing bus fleet components.
  • Reducing costs compared to purchasing new trolleybuses.
  • Minimizing waste and environmental impact through a circular economy approach.
  • Enhancing accessibility and service quality for passengers.

Implementation

The project was initiated by the local public transport operator PKT GDYNIA, in cooperation with Gdynia Public Transport Authority (ZKM) and experts in electric mobility. The implementation process included the following steps:

Selection of Suitable Diesel Buses

  • Mercedes-Benz O405N low-floor buses were chosen due to their durability and availability on the aftermarket.
  • Criteria included three-door configuration, at least four ventilation windows, and a fully accessible floor design.

Technical Conversion Process

  • Removal of diesel engine, gearbox, and fuel system.
  • Installation of electrical drive components, including traction motors, current collectors, converters, and regenerative braking systems.
  • Structural reinforcement of the vehicle’s roof to accommodate trolleybus components.
  • Integration of modern electronic controls and safety systems

Certification and Testing

  • Each converted trolleybus underwent rigorous technical testing to comply with national and EU regulations.
  • Official registration as an electric vehicle, enabling full integration into the public transport network

Operational Deployment

  • A total of 28 diesel buses were successfully converted into trolleybuses between 2004 and 2010.
  • The converted fleet has operated across Gdynia for many years since then, seamlessly integrating into the city’s sustainable mobility strategy

Results & Benefits

✅ Cost Savings

  • The cost of conversion was only 25–37% of the price of a new trolleybus.
  • Allowed for the rapid modernization of the fleet within limited budget constraints.

✅ Environmental Impact

  • Advancing further public transport electrification and a significant reduction in CO2 and NOx emissions due to the shift from diesel to electric power.
  • Reusing existing diesel buses instead of scrapping them resulting in less waste and reduced raw material consumption by repurposing existing vehicles (up to 60% material savings through reuse).

✅ Enhanced Service Quality for Passengers

  • Introduction of low-floor, accessible, low-noise and zero emission trolleybuses improved passenger comfort, particularly for people with reduced mobility.
  • Modernized vehicles greatly increased the attractiveness, popularity and reliability of trolleybus transport in Gdynia.

✅ Enhanced Service Quality for Passengers

  • Introduction of low-floor, accessible, low-noise and zero emission trolleybuses improved passenger comfort, particularly for people with reduced mobility.
  • Modernized vehicles greatly increased the attractiveness, popularity and reliability of trolleybus transport in Gdynia.

Lessons Learned & Recommendations

  • Planning & Expert Consultation: Early involvement of technical experts ensured compliance with safety and performance standards.
  • Flexible Approach: Using different types of electric drive systems allowed for continuous improvement over time.
  • Scalability: Other cities can replicate this model by assessing their existing diesel bus stock and adapting conversion processes based on local infrastructure and needs. In order to assist and facilitate the conversion for others process a handbook on “CONVERSION OF A DIESEL ENGINE BUS INTO A TROLLEYBUS” has been prepared and published by Gdynia experts in the framework of the EU TROLLEY Project.

Gdynia’s approach to converting diesel buses into trolleybuses stands as an exemplary case of cost-effective fleet modernization and circular economy in public transport. This initiative not only supported sustainability goals and demonstrated the viability of circular economy approaches in public transport but also provided a blueprint for other cities aiming to decarbonize their transit networks affordably (up to 75% lower costs compared to buying new trolleybuses).