## 6 Experimental Results  
### Environment and Scenario  
The data that were used for the evaluation were collected during the normal operation of a bus in the city of Poznan. It includes the sequences from two different bus lines: no. 160 and 176. The system starts up automatically when the bus approaches the charging stations requiring no driver input to be enabled, and then steering suggestions are shown to the driver using the HMI monitor in the cabin. Thanks to the fully automatic solution, it was possible to remotely record the necessary data across multiple days whenever the bus was approaching the charging station. For the evaluation, we chose the recorded approaches from a single bus in December 2022 during the usual operating hours from 4:30 A.M. to 11:00 P.M., resulting in 50 sequences of attempted docking to the selected charging station. December was chosen as the most challenging month due to the poor weather conditions (i.e., snow, short sunlight hours, cloudy sky, smog) that affect both driver's perception and GNSS signal strength. We expect that these conditions are the most challenging to the GNSS localisation accuracy in the entire period of the experiment. All the data were recorded to the hard drive of the onboard computer in the form of a _.bag_ file, which is a format used in ROS for storing different message types. It also offers multiple tools for the analysis and visualisation of recorded sequences and also makes it possible to replay the data for simulation purposes. In our case, each _.bag_ file corresponds to a single docking approach so that we can process them individually and verify whether they are complete and contain the data that are necessary for evaluation. The most important data from this perspective are the actual position of a bus and the reference path, generated by the motion planner, as it is necessary to calculate the path  
Figure 12: Human–machineinterface in ADAS system. The top purple coloured bar indicates the path error: that is, the displacement of the bus’s guidance point from the reference path. The main bar provides steering guidance, consisting of a solid blue line visualising the desired steering angle, and a coloured-filled area indicating the actual steering angle. The colour of the bar is sensitive to the value of the steering error: an acceptable error is shown by green colour, while the bigger the error becomes, the colour changes to orange and red. The vertical bar placed on the right side of the window indicates the remaining distance to the charger; at zero, the pantograph is located exactly below the charger. (**A**): At this state, the centre of the rear axis of the bus (guidance point) is more than one metre away from the reference path, and the driver must turn the steering wheel to the right to align the actual steering with the blue line indicating the desired steering angle. The red portion of the right vertical bar shows the bus still has to proceed further to reach the charger. (**B**): The actual and reference steering is aligned with acceptable precision; however, the guidance point is still more than one metre away from the reference path. From the vertical bar, it can be seen that the bus is closer to the goal pose compared to the image on the left. (**C**): At this state, the reference steering angle is shown around zero, and the actual steering angle is shown around the same value. As the driver follows the guidance and keeps the wheels straight, the bus remains on the reference path and finally reaches the goal pose. error and also to determine whether the manoeuvre was successful. For validation and debugging purposes, we also recorded the GNSS data, as it allows us to confirm the RTK mode of localisation.