**4. Wagon 4.0 contributions**

#### **4.1 Train formation and setup**

Assisted brake tests as well as automation in train data handling rely on information on train set-up, especially the order and orientation of wagons is important. Although human operators intuitively capture the order and completeness of the wagon group and convey information, a technical system needs to gather and transfer information explicitly.

In automatic brake test systems currently implemented, the completeness of the wagon group is assured by comparison of the rake to a wagon list transmitted beforehand [14]. This information regarding wagons in the rake and their order may be potentially supplemented by GNSS localisation. The intra-train communication relies on point-to-point radio or mobile communication.

The authors expect that both point-to-point and mobile communication may lead to problems limiting the availability of the systems, for example, in areas with poor cell coverage. Further, the usage of wagon lists for train topology generation may yield disadvantages over the detection of the actual state of the rake, since such lists may contain errors and need to be generated first.

For this reason, the W40 follows a different approach. Each wagon is equipped with controllers at both ends of the wagon. A local area network connects both controllers as well as sensors and actuators installed in the wagons. Adjacent wagon ends are connected by a V2V communication system. This creates a linear network closely replicating the rake structure. Each wagon is able to identify its neighbouring wagons and may share this information on the network. This makes it possible to maintain a digital representation of the wagons in the rake as well as their state on each wagon.

This yields the advantage that communication throughout the train can be implemented comparatively easily and reliably. The physical layer of the wagon-to-wagon interface can be formed by the recently proposed digital automatic coupler [15] or with the help of short-range radio communication. It is reasonable to assume that such a radio connection is at least as reliable as a galvanic connection since a lineof-sight connection is always available. The radio connection between wagon ends is realised with the help of a WifiDirect (trademark of Wifi Alliance) connection. Additionally, a Bluetooth Low Energy connection may be used to measure distances in order to safely connect to the next wagon [16].

Since the W40 concept implements remote-controlled end cocks and BP pressure sensors, as indicated in **Figure 5**, this distance measurement is not strictly necessary since adding wagons to the train consists that are not pneumatically coupled will not lead to a successful brake test, and thus any wrong connections will be contained and will not endanger the mainline operation.

Operating personnel connect to the wagon with the help of Wifi formed *ad hoc* using a smart device such as a tablet. **Figure 6** shows the corresponding user interface.

In the target market of freight wagons, it is reasonable to expect non-equipped wagons. The W40 concept is not intended to pass by any non-equipped wagons. Instead, the basic equipment of the wagon to allow communication and detection of neighbouring wagons (termed W40 class 1) comprises only low-cost, low-maintenance components. The class 1 equipment enables the wagon to identify its neighbouring wagons and to participate in the V2V communication. This equipment uses semiconductors from the consumer range and can be operated for years on battery power; thus no wheel set generator is required.


*Web interface of a device connected with WagonOS showing the train list.*

#### **4.2 Brake test**

An analysis of accidents [17] highlights discontinuities in the brake pipe (BP), untimely brake applications and the inappropriate use of hand brakes and scotches as causes for catastrophic outcomes. Irregularities or damages to the brake rigging or brake calipers reduce the brake effort only for single bogies or wagons, with no significant effect on the train.

The observed failures and errors causing the accidents are


In the investigated cases, all of the above went undetected using the existing brake test procedures conducted prior to the accidents. Most of these are difficult to detect using only visual inspection and the common static brake test procedure. Further, in some cases, the failure developed during the train mission, such as in the Llangennech rail disaster [18].

The W40 approach introduces a novel definition of system borders for brake tests based on the brake-related accidents analysed in Ref. [18]. Based on this analysis, a different split of test steps between brake tests and inspections is proposed.

The effectiveness of visual checks for brake application and release or cylinder stroke needs to be questioned. Such visual checks are costly and do not sufficiently mitigate errors such as discontinuities in the BP.

On the other hand, irregularities in and damages to the brake rigging appear at a very low frequency in accident reports. In contrast to the failures in handling and operation of brake systems reported above, these typically result in the unavailability of brake functionality on single wheelsets, bogies, or wagons. Such singular failures

are not likely to endanger the safety of the train as a whole. From a perspective of the overall safety of the railway system, an automated test based on brake cylinder pressures rather than visual checks of brake block travel may be an appropriate alternative.

The required sensors are robust and cost-efficient pressure sensors for brake cylinder and BP pressure, whereas for the detection of an untimely application of the brake, a position sensor on the brake cylinder is required.

A pneumatic scheme with added pressure sensors is depicted in **Figure 7**. This set-up is able to detect the following states:


3.Brake command state (by BP pressure sensor).

Thanks to continuous measurements of brake pipe and brake cylinder pressures, it is also possible to observe both the propagation of the brake command in the BP and the filling and release time of the brake cylinder. This enables the development of further diagnostic systems, for example, to detect deterioration of the distributor valve or an incorrect brake mode. The propagation also serves as a second channel beside WIFI for the verification of the consist order.

The information on the ongoing brake test is displayed on the user interface screen, effectively assisting the operator in the brake test by providing information formerly obtained by walking to the brake system in question. The user interface is shown in **Figure 8**.

Further, the sensor equipment can continue to observe these values during mainline operation, which improves safety over the singular observation in classical brake tests. The continuous observation is capable of detecting untimely service brake applications as well as inappropriately applied hand brakes.

#### **Figure 7.**

*Pneumatic scheme of a wagon brake system with sensors for BP and brake cylinder pressure, from [13] (CC-BY 4.0).*


#### **Figure 8.**

*User interface displayed during the assisted brake test.*
