Russia: A significant highlight of the INNOPROM 2025 exhibition was the full-scale prototype of the three-car low-floor tram 71-233. This is the first proprietary tram developed by Sinara – Transport Machines (STM), created as part of the holding’s long-term strategy to expand its presence in the urban public transport segment. The engineering group spent several years developing this model.
Work on the 71-233 project began in 2023 at the project office of Sinara – GRT, part of STM. A team of engineers, combining expertise from railway engineering to aviation systems, set out to create a modern tram ready to challenge traditional market players. In 2024, the cab design was already unveiled, assembly of the prototype commenced, and preparations for serial production began in Ekaterinburg. In effect, the creation of the 71-233 model was a clean-sheet design, taking into account the experience of Russian cities and modern international standards.
Key design features
The 71-233 tram features a fully-welded, all-steel load-bearing body frame with the integration of composite materials. The core structure consists of a welded frame and semi-skeletons made from sheet and open-profile elements, eliminating the need for a traditional tubular frame. Vertical frames and longitudinal H-shaped beams are welded into a single, rigid structure, capable of withstanding major bending and torsional loads encountered on challenging track sections.
The roof is constructed from corrosion-resistant sheet material, ensuring maximum airtightness and durability in all climate conditions. Composite sandwich modules are used for the exterior side and end panels, mounted onto the steel frame and fixed with welded joints and sealing adhesives. This modular approach simplifies panel replacement and repair. The use of composites increases body stiffness while reducing overall weight and minimising corrosion. Additionally, the new design allows for flexible interior module configurations, enabling operators to adapt the vehicle to various requirements and facilitating product portfolio development.
The bogie is the key element of the running gear. The low-floor bogie technology of the 71-233 is notable for its unconventional kinematic arrangement. The frame and bolster are of fully welded construction, while the motor-reduction drive unit is mounted externally on a dedicated structural element, the “link”, which is supported on the axle via a bearing assembly and is also spring-suspended from the bogie frame using a set of adaptive springs.
Scheme of the low-floor bogie used in the 71-233 tram. Source: Sinara – GRT patent
The use of adaptive springs in the primary suspension makes the system adjustable, allowing the suspension stiffness to be tuned as required, which in turn ensures a smooth ride tailored to the infrastructure. The external placement of all major components (motor, reduction drive, electromechanical brakes, etc.) on the bogie significantly improves maintainability in depot conditions and reduces maintenance labour.
The tram’s running gear is designed to allow bogie replacement for different track gauges—both the standard Russian 1,524 mm and the European 1,435 mm. The latter is particularly relevant for export potential, but this gauge is also found in Russia, for example in Rostov-on-Don. Accordingly, another prototype of the 71-233 tram fitted with 1,435 mm bogies was being presented at INNOPROM for guests of the Ural Locomotives plant.
The first 71-233 tram from STM at INNOPROM. Source: STM
The traction control system incorporates algorithms to maximise energy recuperation during braking. The 71-233 is equipped with a wheel flange lubrication system, which reduces friction by 20%. This solution has enabled a reduction in noise, while simultaneously extending wheelset life and reducing rail wear. The use of biodegradable lubricant ensures the system is environmentally friendly. According to our estimates, the combination of energy-efficient solutions will reduce electricity consumption on the line by approximately 15% compared to the previous generation of trams.
Interior space and interface
The innovative body and rational interior layout have enabled a longer tram and higher capacity without increasing vehicle mass. The tram can accommodate up to 308 passengers, including 70 seated.
The tram is fitted with wide doors—four 1,340-mm-wide double-leaf doors and two 840-mm-wide single-leaf doors. This arrangement ensures rapid passenger flow and eliminates delays during boarding.
Interior of the 71-233 tram. Source: STM
The interior is designed around the concept of spaciousness and openness. Large windows and light-coloured finishes, together with the absence of podiums in the main passenger area, create a bright and airy environment. The floor is as low as possible with minimal gradients, ensuring accessibility throughout the passenger area.
A modern climate control system with two service zones has been installed, along with an air duct system designed using airflow modelling. The driver’s cab follows aviation principles: an ergonomic seat with four-way adjustment, interactive displays and controls within easy reach, and large glazed panels for maximum visibility and comfort.
Safety technologies
The LRV is equipped with the latest active and passive safety systems. The crash system incorporates energy-absorbing elements in the end cars of the vehicle, reducing the risk of injury to passengers and the driver in the event of a collision. Surveillance cameras are installed throughout the passenger area and cab, and the Govoryashy Gorod (literally Talking City) system is integrated. The automated sand delivery system adapts to track conditions and autonomously enhances safety on any section of the route, including curves, while optimising sand usage to reduce the frequency of refilling.
Design of the tram control panel, presented by STM at INNOPROM 2024
Real-time IoT monitoring of key components has been implemented, enabling control room staff to monitor the operation of motors, doors, brakes and more. This provides a foundation for the future introduction of Level 2 ADAS functions.
Outlook
Mass production is planned to be launched in Yekaterinburg, with the project expected to create more than 600 new jobs. The tram is 100% Russian-made, with 70% of components supplied by companies within the Sinara Group. For example, bogies are manufactured in the Kaluga region at the Lyudinovo Diesel Locomotive Plant, while control and autonomous running systems are produced by IT company Algorithm S.
The 71-233 tram is a platform solution from STM, forming the basis for the company’s entire urban rail electric transport portfolio. The unified architecture includes a set of standardised mechanical units and electronic modules used across all tram models.
In addition, the platform is designed to share its architecture with STM’s trolleybuses and electric buses, which have been in serial production since 2023. This reduces the range of spare parts required and simplifies service centre logistics, while the modular design allows new models to be brought to market quickly with minimal modifications. Furthermore, the external design of all vehicles is unified, from the driver’s cab to the roofline, emphasising family identity and strengthening brand recognition.
Following INNOPROM 2025, trams for 1,435 mm and 1,524 mm gauges are scheduled to undergo running and certification tests, after which the start date for serial production will be finalised. The transition to mass production of the new vehicle will enable STM to enter the light rail market and play an active role in the renewal of tram fleets in the regions.
In memory of Dmitry Sergeyev, a talented engineer and designer who made a significant contribution to the development of the Sinara tram family.
Authors:
Nikolay Bogoslovsky, Head of Product Development, Sinara – GRT
Grigory Menaker, Head of the Mechanics Group, Sinara – GRT Design Bureau
