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Modern interface means safer metro services

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The paint on the walls has just dried, the office furniture has been designed and is in place. The physical work environment for the traffic managers on SL’s red line is ready for them to move in. But there is still a lot of work to be done in the project – work will now start on the digital work environment.

I joined the project nearly two years ago. I work in a project group that places orders and assesses the solutions developed by the supplier Ansaldo. You might say that I guarantee the usability of the software that the traffic managers will be using.

The time had come for the old analogue system to be replaced. A new digital signalling system is a must, as the analogue system is unable to manage more frequent services, while at the same time passenger numbers keep on increasing in Stockholm.

One of the biggest challenges for me is that all of the old systems have to be brought along – it costs too much to buy new ones, as they’re not completely outdated. This is why a lot of technology and integration is being prioritised in the project.

“Traffic managers are ultra-specialists with a high learning capacity,” is something I often hear. That may well be true, but take a look at the picture above. Here they haven’t taken stressful situations into account, or the fact that you have to be able to gain a rapid understanding and overview. Maybe you work as a traffic information officer in your team and you don’t have the experience of the technology on the track but still need to understand symbols and warnings.  Or perhaps you work outside the control room and are interested in reading logs to check how the track is behaving at the moment?  It’s important to make the threshold as low as possible, so that different roles are able to work quickly and get it right.

I’ve done a lot of work on reducing the number of colours used in the system. There used to be 14 different colour codes to indicate different things. People also wasted distinctive colours like green, red and yellow on messages that were more or less the same.

You should have no more than 4-6 colours. I simplified the colour scheme radically and used six colour codes, each with its own “message”. Partly because it’s important to see the difference between colours, but also because it has to be easy for the user to remember the significance.

The first three colours mean that something requires attention. Red is always an alarm colour, it requires intervention. The lilac colour means that the traffic manager must be aware of something and plan an action. Yellow indicates that something is deviating from the norm, but that there is no particular danger.

The blue colours indicate normal active events, to depict the flows. Black is used for switched off and green shows a special case in which optical signals actually show green lights on the track, as in older systems where the trains are not connected. This is what the new graphical user interface for the traffic control system looks like. The traffic is flowing well in the upper view, and in principle everything is blue.

The image below shows the alarm modes, the three markings that are red indicate that the traffic manager must rectify the problem.

Take a close look at the image before directing your attention to the old interface below. Easier or harder to discern the alarms? The alarm indicators are actually in exactly the same places in both layouts. The images provide a clear illustration of why you should tone down the background information and highlight what it most essential.

The size of characters and symbols is another aspect that I’ve been looking at. Here a colleague and I have calculated the distance between the eye and the screen. We then used standards to calculate how large a character on screen should be. I have to take several distances into account in a traffic control centre, which makes it more difficult. There it’s not just your own workplace that’s important, you also have to have a good view of the large summary screen in which all roles have an interest.

There is a lot of natural light in the red line’s new control room, both from the side and also from above through a number of skylights. We have tried to retain good light inflow, as it keeps people awake and alert.

But it brings one question to the fore: is it better to have a light or dark background on screens close to you and on the wall? There is no correct answer to this, it depends on both the environment and the task in hand. We can’t control how the eye focuses – it will adapt to the brightest area in the field of vision. So you have to make sure that the interesting feature in the environment, what I’m trying to look at, is in the brightest area. I’ve also worked on balancing the contrasts. As users would rather switch on the lights at night than shut out the daylight, we chose a light background for the screens.

Yes … it’s great working with control rooms. All of the things that can be seen as details contribute towards a greater whole. But the best thing of all is when you achieve something that actually improves the product and thus improves the work environment – which enables good traffic management work.  Which in turn has a major impact on transport services in Stockholm. That we can contribute to such great value for society – that’s something worth working for, I think.


Do you want to find out more about designing control rooms and command centres? Register for our inspirational lecture “A Focus on Control Rooms” on 7 October. Part 1 of this series about the control room on SL’s red line is also available to read here in the blog:  Sustainable work environment for SL’s traffic managers.