Displays for transportation

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Passenger information visualization systems

Passenger information is an extremely important part of any trip. Especially if it is update in real time. This creates increasing demand for dynamic content visualization solutions. The challenge, therefore, is to arrange travel messages in such a way that they are clear, accessible, and useful in locations important from the passenger’s point of view. As a result, transportation-related spaces are filled with various types of displays in the form of timetables, boards announcing arrivals and departures, digital signage leading to the bus stops, stations, gates, various vending machines such as ticket machines or parking meters, but also the information we see inside vehicles.

Providing the best possible access to the displayed content

Passenger information systems are still dominated by LCD-TFT displays, which are effectively displacing previously used solutions such as LED displays.

It is crucial from the passenger’s perspective to reach the desired content, so – in addition to placing the screens in appropriate locations – it is important to ensure optimal readability of the content presented on them. It is worth using solutions with exalted optical parameters, each time adapted to the conditions of the environment. Here, among other things, brightness will be key – spaces such as train stations and airports are intensely lit, so solutions with a brightness of at least 1000 cd/m2 are placed there. Full viewing angles (achieved, for example, with IPS matrices) will also be important, allowing content to be read from any plane. Some of these types of carriers are designed to operate around the clock – continuously. In such cases, it is best to use LCD-TFT displays with the longest possible LED life. For some models, this parameter is specified at 100,000 hours, which – given the right environmental conditions – can promote trouble-free operation for up to 10 years.

The parameter to pay attention to when implementing LCD-TFT displays in outdoor applications is the operating temperature range. For number of models it ranges from -20 to 70°C, which is considered “wide” in the industry, and it performs well in typical applications. However, in extremely low or hot temperatures, exceeding the standards indicated by manufacturers, the device should be additionally equipped with heaters or fans to maintain the appropriate temperature. When the LCD-TFT module is placed in a sunny location, the brightness of 1000 cd/m2 will be insufficient. Achieving optimal content readability will be then possible at a brightness of at least 1500 cd/m2 (and certainly at 2500 cd/m2). What is more, in such places it is a clever idea to use LCD-TFT displays with implemented high-TNI technology, which nullifies the risk of liquid crystal damage when exposed to direct sunlight. Any electronics intended for use in outdoor applications needs protection from potential contaminants such as dust and water. This requires implementing additional protection – one of the primary ways to secure display modules are gaskets. In addition, all electronics should be housed in an enclosure with an appropriate level of waterproofing.

E-paper as an alternative to LCD-TFT displays?

EPD displays may be an interesting alternative to LCD-TFT displays. For transportation applications, e-paper solutions are increasingly being used as timetables.

E-paper technology will be perfect where paper is a common solution. They are similar in terms of content readability – the only requirement for e-paper, as with paper, is access to an external light source. At the same time the EPD technology, when compared to other methods of data visualization, excels in energy efficiency – because the current is consumed only when the image reloads. If e-paper operates outdoors, e.g., at bus stops or stations, it is possible to make them more eco-friendly by powering them with green energy, like solar panels. A shortcoming of EPD technology is the limited

operating temperature range, most often between 0-50°C. Here, however, one can apply a similar solution to LCD-TFT display, which is to introduce heaters or fans to ensure the optimal temperature for trouble-free operation of all the electronics inside.

E-paper-based solutions that can be successfully used as timetables, for example, are the USEC and USEM modules designed by Unisystem engineers.

Touch solutions in transportation

In devices intended for public spaces, capacitive solutions will work best. Their design and method of operation make them resistant to heavy use, without being as susceptible to distinct types of mechanical damage.

Protective or decorative glass is used in all touch-enabled display modules. By changing glass thickness, you can create display solutions that will reduce the risk of damage to the screen surface not only in case of accidental damage, but also in the intentional acts of vandalism. Additional anti-shatter (AS) coating gives even more protection, because when the screen surface is broken, AS coating will prevent the spread of glass shards.

Touchscreen modules are customizable according to application requirements. Enhancements such as water rejection mode (which detects the presence of water on the screen surface) and palm rejection (which detects the presence of larger objects on the screen surface) may be necessary to ensure that the display module functions properly even under adverse circumstances.

Display solutions for vehicles

Screens are also increasingly popular inside vehicles. For example, a display solution for presenting the actual route. And the technological advance here is significant, since not so long ago most popular were route lightboxes, which today are replaced by wide-format LCD-TFT displays. When implementing any electronics in vehicles, it is necessary to meet the requirements defined by specific standards. One of them is EN 50155, known in the industry as the “railroad standard” because it provides guidelines for the use of electronics in rolling stock. Some of those describe required resistance of equipment to signal interference and vibration.

LCD-TFT displays are the most common choice for this kind of use in transportation. Our suppliers offer products that are created with transportation application in mind (and their primary advantage is to meet the requirements of the EN 50155 standard). Designers and engineers just need to choose parameters like those that affect the readability of the content presented on the screen. Transportation solutions should have the best possible quality – the highest possible resolution, proper brightness and contrast, and full viewing angles.

When screens work in vehicles, a common issue is limited space available inside – like in train or subway there is just a small gap between the door and the ceiling to display current route. In this case the customized solutions – tailored to the customer’s requirements – will fit in best. One can achieve special sizes and shapes by cutting LCD-TFT matrices, which means the literal cutting from standard LCD-TFT matrices, usually found in 16:9 format. The cutting is then sealed to prevent damage to the liquid crystals, as well as to protect against the ingress of contaminants. A noteworthy way to achieve unusual shapes and sizes of LCD-TFT displays is the TARTAN technology developed by AUO engineers, which is based on native photomask manufacturing processes.

Displays for ticket validators dispensers

Although LCD-TFTs dominate in transportation industry, there are still niches implementing classic LCM displays, like the cash registers. These displays are rather small-sized modules on which content presents in contrasting ways (e.g., light content on a blue background or dark content on a yellow-green background). They are perfect for communicating short messages. LCM displays are resistant to shock and vibration. They can work for years without single failure. What is more, those are cost-effective solutions, when compared to other data visualization technologies, because of low production and maintenance costs in the end device.

However, one can expect that in the near future, the LCM technology will be fully replaced by LCD-TFT, especially as public transportation vehicles like streetcars and buses are increasingly using devices that can punch a ticket, but also sell it and make payment using a bank card or smartphone.

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