IMC Electric bus

Solaris Trollino with IMC in Esslingen am Neckar, Germany.

An IMC electric bus (In-Motion Charging electric bus), also known as a battery trolleybus or trolleybus with extended autonomous run, is an electrically powered public transport vehicle that draws power from an overhead contact network (catenary) via trolley poles while simultaneously charging an on-board traction battery. This technology allows the vehicle to operate continuously: drawing power and charging while under the overhead wires, and operating as a battery electric bus on sections of the route lacking infrastructure.

This concept is a further development of the traditional trolleybus, evolving from vehicles with small auxiliary power units for emergency use to modern systems where vehicles operate autonomously for significant distances, often between 15 to 70 kilometres (9.3 to 43.5 mi).

Modern In-Motion Charging (IMC) trolleybus systems can offer significant cost advantages over fully battery-electric bus networks. Studies indicate that upgrading existing trolleybus infrastructure to IMC can reduce capital costs for rolling stock by approximately 50% and lower operational expenses by around 20% over a 15-year lifecycle compared to deploying new battery-electric buses. When building an IMC system from scratch with partial overhead lines, capital expenditures can still be roughly 10% lower than a fully battery-based system, due to reduced battery capacity requirements and more compact vehicle fleets.

Terminology

The term In-Motion Charging (IMC) was introduced as a branding concept by Erik Lenz of Vossloh Kiepe (now Kiepe Electric) in 2014 during the trolley:motion conference in Hamburg. The terminology was intended to improve the public perception of trolleybuses by highlighting their main advantage over static-charging electric buses: the ability to recharge batteries while transporting passengers, eliminating stationary charging times.

In Russia and CIS countries, these vehicles are often referred to as a Trolleybus with Extended Autonomous Run (Russian: Троллейбус с увеличенным автономным ходом, abbreviated as TUAH) or simply an Electrobus with dynamic charging.

History

Off-wire power developments

On this articulated , the operator guides poles to the wires. Modern IMC buses can often reconnect automatically.

The concept of a trolleybus operating away from wires dates back to the early 20th century. While the word trolleybus originates from 1882 when Werner von Siemens presented an early electrically powered vehicle, modern trolleybuses have long used sliding current collectors.

In the United States, the Public Service Company of New Jersey, in conjunction with the Yellow Coach Manufacturing Company, developed "All Service Vehicles" (ASVs) between 1935 and 1948. These were trackless trolleys capable of operating as gas-electric buses when off-wire.

From the 1980s onward, systems such as Muni in San Francisco, TransLink in Vancouver, and Beijing, among others, began buying trolleybuses equipped with auxiliary batteries or diesel engines to allow them to operate over longer distances off-wire or to bypass route blockages.

Dual-mode buses

A dual-mode bus operating as a trolleybus in the Downtown Seattle Transit Tunnel in 1990.

Before the maturity of high-capacity lithium batteries, dual-mode buses were common. These vehicles used overhead wires for electric power and a separate diesel engine for off-wire travel.

• Seattle: King County Metro used special-order articulated Breda buses in the Downtown Seattle Transit Tunnel from 1990 to 2005.
• Boston: The Massachusetts Bay Transportation Authority (MBTA) used dual-mode buses on the Silver Line (Waterfront) route from 2004 until 2023, when they were replaced by diesel hybrids and battery-electric buses.

Shift to IMC

With the development of battery technology (specifically Li-ion) in recent years, the focus shifted from diesel auxiliary units to purely electric autonomy. In Shanghai, experiments began in 2006 with "capacitor energy storage" electric buses that charged at stops. By the 2010s, the "TROLLEY project" in Central Europe was established to promote sustainable trolleybus strategies, leading to the widespread adoption of In-Motion Charging to extend routes without building new infrastructure.

IMC electric bus in Dayton, USA.

Technology

In-Motion Charging batteries charging at Palmovka, Prague.

IMC trolleybuses are equipped with a high-capacity traction battery adapted to the specific line profile. The vehicle typically operates with a mix of wire connection and battery power (e.g., 60% of the time on the wire and 40% on battery).

• Charging: Charging occurs dynamically while the vehicle is in motion under existing overhead wires. Current transfer can reach powers up to 500 kW (e.g., the IMC500 system).
• Range: Modern units can travel significant distances off-wire, often in excess of 15 kilometres (9.3 mi).
• Advantages: Unlike stationary charging electric buses (Opportunity Charging or Overnight Charging), IMC does not require long charging stops at terminals or the construction of dedicated charging stations in public spaces. It allows for the electrification of bus routes by extending existing trolleybus lines.

Comparison with other electric buses

Feature	Overnight Charging (ONC)	Opportunity Charging (OC)	In-Motion Charging (IMC)
Charging Method	Slow charging at the depot (overnight)	Ultra-fast charging at specific stops	Dynamic charging under overhead wires
Infrastructure	Requires high-power grid connections at depots	Requires charging stations at stops/terminals	Uses existing trolleybus network; no new chargers needed for extensions
Downtime	4–10 hours (in depot)	5–25 minutes (at stops)	None (charges while driving)
Battery Size	Large/Heavy (reduces passenger capacity)	Moderate	Moderate/Small
Heating	Often requires diesel heater in winter	Electrical (limited)	Electrical (powered by overhead wire)
Grid Impact	High peak load at night	High spikes during fast charging	Distributed load throughout the day

Some operational issues have been noted in systems such as Saint Petersburg and Barnaul, where overheating of the contact wire can occur due to high charging currents if the vehicle is moving too slowly or is stationary while charging.

Global adoption

Asia

• China: China has been a leader in adopting battery trolleybuses. Beijing and Shanghai operate massive fleets. In Beijing, BRT lines were converted from diesel to dual-source trolleybuses between 2015 and 2016. The city of Baoding launched a system exclusively based on battery trolleybuses.
• Saudi Arabia: In 2011, the King Saud University in Riyadh established a system with 12 articulated trolleybuses for campus transport.

Europe

• Germany: Cities like Solingen, Eberswalde, and Esslingen utilize IMC technology. In 2020, Berlin announced plans for a new trolleybus system with 190 battery trolleybuses, though plans were shifted toward battery-only buses in early 2023.
• Switzerland: Zürich, Geneva, and Lucerne operate extensive networks. For example, the "Swiss Trolley Plus" by Carrosserie Hess was tested in Zürich.
• Czech Republic: Cities like Prague and Ostrava have integrated battery trolleybuses to extend routes into areas without wires.
• Italy: Lecce opened a dual-mode system in 2012.

North and South America

• USA & Canada: San Francisco (Muni), Seattle (King County Metro), and Dayton operate large fleets of trolleybuses with battery off-wire capability (replacing older dual-mode diesel units). Vancouver also utilizes these systems.
• Argentina: Cities like Rosario and Córdoba have imported Trolza vehicles with autonomous capabilities.
• Mexico: Mexico City has integrated Yutong battery trolleybuses into its updated fleet.

Russia and Belarus

Trolza-5265 with dynamic charging in Saint Petersburg.

The region has seen aggressive development of "Trolleybuses with Extended Autonomous Run" (TUAH).

• Saint Petersburg: Launched a major initiative in 2017 to expand the network without building new wires. By late 2023, over 13 routes and 200 vehicles were operating, linking metro stations to new housing developments.
• Belarus: Manufacturers BKM Holding and MAZ produce IMC buses used domestically (Minsk, Gomel, Vitebsk, Grodno) and exported abroad. Minsk has utilized IMC technology to return trolleybus service to the entire length of Independence Avenue.
• Other Cities: Novosibirsk, Krasnodar, Cheboksary, and Khabarovsk have actively purchased and deployed IMC vehicles to extend routes to suburbs.

Manufacturers

Major manufacturers of IMC buses and propulsion systems include:

• Kiepe Electric (Germany/USA) – Provides electrical systems for chassis manufacturers.
• Solaris Bus & Coach (Poland) – Produces the Trollino series.
• Carrosserie Hess (Switzerland) – Produces the lighTram series.
• Van Hool (Belgium) – Produces the Exqui.City series.
• BKM Holding (Belarus) – Produces the 32100D and Olgerd series.
• MAZ (Belarus) – Produces the MAZ-203T series.
• PC Transport Systems (Russia) – Produces the Admiral series.
• Yutong (China).
• Trolza (Russia) – Defunct, formerly a major supplier of the Megapolis series.

See also

• Trolleybus
• Electric bus
• Battery electric bus
• Dual-mode bus

References

This article "IMC Electric bus" is from Wikipedia. The list of its authors can be seen in its historical and/or the page Edithistory:IMC Electric bus. Articles copied from Draft Namespace on Wikipedia could be seen on the Draft Namespace of Wikipedia and not main one.

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