Bench grinders

Our 'crazy gadgets', a tour of Metro's most extravagant, unknown and useful vehicles

You've seen so much of Metro that you may well think you've seen it all. Of course. We're sorry to tell you that you're probably wrong... Not only have you not seen everything, but in our world there are things you can't even imagine. Yes, such as an extensive and varied collection of trains and other 'mobile contraptions', rare to the average person, but essential in specialised missions of maintenance, inspection and repair of tunnels, tracks, catenary, etc. These are the Metro's auxiliary vehicles, our 'craziest gadgets', which we invite you to discover here at Crazy About Metro.

1965 saw the release of 'The Great Race', a Blake Edwards film starring Jack Lemmon, Tony Curtis, Natalie Wood and Peter Falk, the main plot of which is the celebration of a crazy international race featuring the most outlandish and bizarre vehicles of the time. The film was a success and had a sequel in the form of a cartoon called 'Wacky Races', where the most extravagant cars reached extreme exaltation. Well, if this same plot had a replica in the railway world, Metro de Madrid would undoubtedly achieve a prominent place in the cast thanks to a family of trains and other very unique and difficult to know 'crazy gadgets'.

This is the 'family' of Metro's auxiliary vehicles, used in the maintenance and repair of our network so that trains can run at all times with the utmost reliability, day after day, 365 days a year. Their work is mainly carried out in the early hours of the morning, when Metro closes its doors to passengers, between 2 am and 6 am, making them difficult for the general public to see.

These vehicles are unique, highly specialised and capable of performing a multitude of tasks ranging from treatment of the railway rails (the rails on which trains travel), inspection and diagnosis of the network, catenary and track, tamping of ballast (the layer of gravel spread to settle the railway sleepers), loading of coils, rails and other materials, intervention in train incidents, cleaning of manholes and drainage channels, as tugs, and for working at heights, with lifting towers and cranes, among others.

This special fleet is currently made up of 80 auxiliary vehicles divided into 10 specialities, which in turn are grouped into three main types: diesel traction vehicles, towed vehicles and electric traction vehicles. They are as follows:



Tamping machine

Reel holders

Bivials (with truck wheels)

Bench grinders


Auscultation trains

Rail carriers



The dresins are the largest group of auxiliary trains with up to 8 types of specialities. We will devote some time to them to learn more about them.

Tower dresins. They are so called because they have a tower the main mission of which is to work at heights, as well as incorporating elements such as lighting, air intakes, electrical sockets and a control desk to manoeuvre the train from this elevated post. These dresins are mainly intended for the maintenance of the overhead line, the catenary, that supply the trains with electricity.

Tower dresins

Dresins with crane and loading platform. These vehicles are equipped with a loading platform, which varies in size depending on the manufacturer's series, and a crane to facilitate loading and unloading operations of all types of shipped materials. They are mainly intended for track maintenance.

Dresins with crane and loading platform  Dresins with crane and loading platform

Dresins with loading platform without crane. These are vehicles with a variable load area that can also be used to tow wagons. They are available with a single cab and with opposing cabs, for driving and operating in both directions. Within this group, there was a dresin that had a concrete mixing vat, which has now been replaced by another loading platform.

Dresins with loading platform without crane

Warehouse dresins. Specialised in transport and storage of several materials and tools. On their sides they have a folding lifting platform to facilitate loading and unloading at platform and track level. They have a load capacity of 1,500 kg.

Warehouse dresins

Manhole dresins. Vehicles designed for the extraction of sludge for the unblocking of manholes and gutters in our network. They are equipped with a tank dedicated to the transport of liquids and solids from the cleaning of wells and sewers and have a high-pressure pump for the hydrodynamic cleaning of the pipes.

Manhole dresins

Rail welding dresins. their design responds to the need to provide assistance and transfer of all types of material and tools for track maintenance. The design of these vehicles is variable. Two of them form a coupling tandem in which the first has a large loading area for transporting rails and the second is used exclusively for transporting tools and staff members. The other vehicle is devoted to the transport of light material and tools.

Rail welding dresins

Intervention dresins. Vehicles designed and equipped with all types of materials and tools to provide assistance to trains within the Metro network. Specifically, these dresins form a coupling tandem when they are moved, with one of them having a large loading area and incorporating a crane to facilitate the movement of materials, while the second having a storage area for the necessary equipment and tools.
Intervention dresins


We leave the world of dresins to visit other auxiliary vehicles with really interesting and specialised functions. Let's dive in!

Tamping machines. These are vehicles specialised in the treatment of the trackbed, in particular the ballast, which is the layer of gravel or small stones spread to settle and support the railway sleepers. They have a tamping unit that stabilises, levels and conditions the trackbed when it is made up of ballast.

Tamping machines

Bivials. The design of these vehicles allows them to be driven both on roads, with truck wheels, and on railway tracks, as they have hydraulically-operated axles with railway wheels. One part is initially designed to transport the material and tools required for any type of intervention. Another of these vehicles has been designed primarily for overhead line (catenary) work. They can also be used for work involving signalling installations, tunnels and other hard-to-reach areas.


Grinding trains. Specialist rail maintenance vehicle commissioned in 2008. It is a five-module articulated train in which car A is the propulsion unit. Car B is the laser measuring vehicle and the remaining three cars, C1, C2 and C3, have the grinding trolleys with which the rail surface defects are repaired. Various types of rotating grinding wheels are available for the specific treatment of the rail geometry. This train is prepared to run on heavy metro, light metro and tram lines. Several modifications were made to improve it between 2017 and 2018.

Grinding trains

Grinders. Another special vehicle designed for mechanical rail treatment. It incorporates a grinding unit consisting of 16 grinding wheels and its own drive system.


Rail carriers. Vehicles constructed and designed for the transport of rails.

Rail carriers  Rail carriers

Hopper cars. Designed specifically for the transport of aggregates: sand, gravel and grit commonly used in tunnel works and repairs.

Hopper cars

Gondola cars with and without crane. Due to the distance between bogeys (which are the systems that encompass all the suspension, braking and running gear elements of a train), these cars are specialised in loading track coupons and other types of materials.

Gondola cars with and without crane  Gondola cars with and without crane

Hinged-edge cars with and without crane. These are cars on which, in some cases, the sides of the load area can be hydraulically folded down. This operation is done manually on other vehicles.

Hinged-edge cars with and without crane  Hinged-edge cars with and without crane

Reel cars (reel carriages). These vehicles are designed for the transport of reels for the installation of catenary wires. They are used exclusively for overhead line work.

Reel cars

Bench grinders. The speciality of this machine is the removal of grease from the rail and the surface treatment of the rail. It lacks autonomous propulsion and is towed to the work area by other vehicles.

Bench grinders

Special vehicles (auscultation train). Metro de Madrid converted the R-2025/M-2026 unit into an Facilities Auscultation Vehicle (FAV), renumbered as AR-101/AM-102. This unit is designed to monitor the condition of the track and overhead line throughout the Metro network, for which it was equipped with a second pantograph for wide gauge lines. It has advanced auscultation systems to make all kinds of measurements. These systems are based on optical technology, laser group, infrared thermographic camera, video, noise analysers, accelerometers and other recording equipment.

Auscultation train  Auscultation train

Classics. These are former passenger cars, mostly 500 series, adapted as auxiliary vehicles. This adaptation has been different according to the assignment of each vehicle. All are engine trains, with two pantographs, for wide gauge and narrow gauge, so they can run throughout the network at 600 volts continuous. These trains were built between 1924 and 1964 and converted to auxiliary vehicles between 1980 and 1994. Four of them were used for train towing and two for intervention.

Self-propelled tractors for incidence intervention

Self-propelled tractors for incidence intervention

Classic tug

Classic tug

Classic twin-voltage tug

Classic twin-voltage tug


Most of the vehicles we have just seen were built by third-party companies in accordance with Metro's requirements, but some of them, mostly dresins, were partially built by the company itself, between 2009 and 2011, in an attempt to gain experience and reduce costs.

This mainly involved crane platforms, environmental and welding vehicles. At the time, Metro reached an agreement with several manufacturers for our workers to "perform 22% of the workload, with the aim of allowing Metro specialists to gain experience. Mixed teams of workers from the manufacturers and Metro were trained and it was carried out", as Francisco García Rodríguez, head of the Dresin Macrosection, explains.

"The manufacturer created the structure of the carriage and the engine, and then Metro took care of all the electrical wiring, the creation and assembly of the control desks, and the connection boxes and equipment, among other elements." "Everything was assembled in our workshops and we also carried out the set-up tests. It was a positive experience because of the knowledge we gained."

The auxiliary vehicles respond to unique designs tailored to the needs of its major customers, which are trackbed maintenance services, overhead line maintenance and construction sites. According to García Rodríguez, "in the end, the design of these machines is the result of a joint decision between users, who will be working with them, and the engineering department, which is in charge of making the specifications. Basically, the design of the machine, he continues, depends on the needs of its operators, which is why each vehicle is so different, so handcrafted and so specific."

Most of these vehicles are operated by Metro's Track and Overhead Line services. María Teresa de los Ángeles de Miguel, expert Maintenance manager, stresses that there are many variables to take into account in its design, "such as the gauge and the layout of the network itself, which conditions the access of some vehicles, to give just a few examples. We have to take all the requirements and all the conditions of our network into account in order to give final shape to the design and decide what its use will be and what needs it has to cover."


The tightening of anti-emission measures also affects Metro's auxiliary vehicles and their future, which is increasingly geared towards the comprehensive electrification of their propulsion systems. Metro is studying technological alternatives so that its auxiliary vehicles can continue to operate in coming years. At the moment, it is a bit like the automotive industry, the current customers of which are already seriously considering the purchase of electric or hybrid cars.

But unlike cars, where there is already a lot of technological development, "in the railway industry we are still in pilot and prototype processes, and the manufacturers of this type of vehicle still find it difficult to assimilate change, even more so in customised developments, as in our case", says María Teresa de los Ángeles. "We are facing an important challenge that we have to face, step by step, because everything related to new technologies makes us take a cautious approach; but we have to move forward. This is increasingly required by regulation."

The future of auxiliary vehicles is entering a new chapter, with its lights and shadows, although there is no doubt that we will continue to see and study them, since without them, the maintenance of an infrastructure such as that of Metro de Madrid cannot be conceived. We haven't talked about its past in this Crazy About Metro, but we can assure you that it is a whole other world full of interesting surprises, starting with its origins... which already spoke of the expertise that Metro's pioneers had to develop in those early days. But this is a story for another day that we will tell you here at Crazy about Metro of course.


1919 Airline Dresin