Digital LCD Displays in Transit Venues

With indoor environments, everything is nice and comfortable. It does not rain inside, temperatures and humidity levels are controlled, the sun does not shine indoors, ambient light conditions do not change that much, the air is clean, electrical power is consistent, the wind does not blow and vandalism is rare. Basically, digital displays deployed indoors are in a controlled environment in virtually every respect.

However, in transit settings, everything changes — and it changes dramatically.

Most transit venues are outside like bus shelters or semi-outside like train platforms or subway entrances. Even when they are underground, these venues are not as clean and controlled as true indoor environments like shopping malls. Not even close. Brake dust from trains and buses is a major concern. Digital displays deployed in these areas are in an uncontrolled, harsh environment that is constantly changing. Anything can happen to them. Therefore, it’s important to consider many factors and how they will affect your digital display initiative before choosing and deploying digital LCD displays.

Conditions Outdoor Digital Displays Have to Endure

It’s imperative to keep all of the factors in mind when evaluating outdoor/semi-outdoor displays. While all of the factors must not be ignored, special attention should be given to the impact of the sun. 

The sun puts out an incredible amount of energy that cannot be overlooked. Before placing displays in direct and indirect sun conditions, consider:

• Sunny environments require high-bright displays for optimum viewing.
• Display luminance should normally be between 1,500 to 2,500 nits or candelas.
• Brightness should be measured through cover glass/film, not just at the surface of the LCD.
• Displays that maintain set brightness levels over time are highly preferred — up to 10 years.
• Most displays will naturally lose 10 to 12 percent brightness per year. This is not good.
• Some displays will lose 10 to 15 percent brightness in hot or cold ambient conditions. Also not good.

Solar clearing of the LCD screen is also a primary concern. With direct sunlight and a backlight at full brightness, the LCD crystals receive a large amount of heat and could go through a phase change from solid to liquid, causing black blotches on the screen. This solar clearing will cause degradation in the display thereby reducing the operating life. To prevent solar clearing several factors must be addressed. 

• LCDs are rated to different temperatures; 68C, 80C and 110C. The higher the better, so ask your hardware provider which LCDs they use and the clearing point temperature of the LCD cell.
• Cold cathode fluorescent lamps (CCFLs) are inadequate for outdoors. Only use LED direct backlight systems. More reliable, longer life, less power consumption, better uniformity. 
• Ambient light sensors should be used to automatically adjust backlight brightness based on light conditions.
• Avoid digital displays that are optically bonded to cover glass. If glass is broken then the expensive LCD is also lost. Also, they are more difficult to keep cool in direct sunlight. 
• Cooling systems must be robust and reliable and consume minimum power and take up little space. 
• The sun is worse in winter with clear skies/lower haze than in the summer.
• East/west orientations are worst. North/south orientations are best.

There is a great deal to consider when thinking of how the sun alone will impact outdoor displays. The LCD is not the only critical component that is affected by the harsh environments. Most electrical components are rated up to certain temperatures and cannot be exposed to moisture or particulate debris. Consider the following when it comes to the impact of temperature and humidity on outdoor/semi-outdoor digital LCD displays.

Transit displays must:

• Be designed for ambient temperatures down to -40F and up to 122F.
• Be designed and validated for high temperatures and direct sun load.
• Have a sealed display to prevent condensation forming inside the cover glass.
• Have a start-up procedure for low-temp power up if temperature is below -40 F.
• Be designed for excessive shock and vibration
• Plan for when the display is not to be run. Consider just turning off the backlight, not the entire digital display.
• Have embedded electronics, such as player, modem, etc., that are rated for internal display temperatures.
• Cooling is critical. Conventional A/C systems will drip, require maintenance and consume significant power. Pick a display that has the fewest failure mechanisms. If the cooling system fails, the display will too. Consider alternative cooling methods.
• Be prepared for how temperature fluctuations can affect brightness. 
• Digital display and the mounting structure must be able to withstand significant wind loads, including gale winds and hurricane force.

While the considerations related to sun, temperature and humidity may seem overwhelming, once they are factored into your outdoor display purchase and deployment, you can rest easier knowing you have taken every precaution to protect your investment. Beyond environmental conditions, also mull over installation, operational and service conditions.

Installation and Operation Requirements

If you are thinking of placing your digital displays on or near public property, you would be wise to do the research about the area. Cities may require permits and there could be restrictions relative to full-motion video content or static transitions, especially near streets. Find out the rules about nighttime operation. Many structures on public properties must be certified by a professional engineer and union or safety personnel may be required for the installation. Beyond government regulations, it is important to consider some of the more practical issues that are often times overlooked.

Communication to your display through a cellular modem must be reliable. How is the cellular service in the area? Cellular service has proven to be more reliable than Wi-Fi. How will power be run to the display, and who is responsible for paying for it? Remember, outdoor displays consume three to five times more power than indoor. Furthermore, power comes in many different forms. It's a good idea to get a display that comes with a universal power supply of 85 volts to 265 volts. Also, check if the complete digital LCD display, housing and cooling can operate on the available power so additional power does need to be provided.

The investment required to implement an outdoor digital signage campaign is not trivial, but don’t be shortsighted and only consider the upfront capital costs (CapX). Take the time to find a hardware solution that minimizes the operational costs (OpX). While power costs can be easily calculated once you have the total annual power consumption, the service costs can be more unpredictable. Vandalism, power outages, periodic cleaning and emergency maintenance can add up to a sizeable chunk of money. The following are specifications you should look for in an outdoor digital display:

• What type of cover/safety glass will be used? It must be able to withstand a beating.
• Glass should be separate from the LCD screen, that way you can replace damaged glass without replacing the LCD.
• Can the digital display be serviced in the installed position? Very important.
• How easy is the service considering that repairmen will be working in outdoor conditions, such as cold, rain, wind-blown dust?
• How modular are the replacement components?
• Can the display be controlled, diagnosed and updated remotely?
• Can the display report back operational data and alerts to the network operations center?
• Can the embedded player, 3G modem and switch be automatically or remotely re-booted?
• How intelligent is the display? Can it verify that the correct image is being displayed on the screen?
• Are there provisions for the mini-UPS system so unit can “phone home” if it experiences a failure?
• What is the sealing rating of the display? NEMA 3, IP 54, etc. 
• How is the unit protected from insects and rodents?
• The glass should have an anti-reflective (AR) coating to reduce reflections from 8 percent to under 2 percent. AR coating helps with reflections from buildings, cars and direct sun.
• Does the paint finish provide protection against harmful UV rays over time?
• What is the overall projected life-cycle of the display? Three years, 5 years, 10 years? This factors greatly into the ROI model.

Though there are many considerations and questions that come with properly deploying outdoor and semi-outdoor digital LCD displays in transit venues, the benefits of reaching the out of home (OOH) marketplace are significant. The fact that these displays can provide day-parting and emergency alerts is huge. Advertisers can now decide when they want their ads run, such as Starbucks in the morning, McDonalds at noon, Bud Light in the evening, to better target their desired audience. City officials now have an immediate way of communicating schedule changes or delays to commuters and they can take control of the entire inventory of digital displays in case of an emergency like Hurricane Sandy in New York City. This is all possible by going digital.

Digital LCD displays for transit venues are not re-packaged indoor displays. Because of the unpredictability of the transit environment, outdoor displays must be both intelligent and robust, and they need to have a long lifecycle to justify the investment.

With temperature variations, brake dust, constant vibration, sun load and the elements provided by Mother Nature, transit venues do not provide for a comfortable living environment for digital displays. However, by researching and asking the pointed questions outlined above, you will be better prepared to select the best solution for your application.

Peter Kaszycki is the president and CEO of LG-MRI, an Atlanta-based provider of robust digital LCD displays for outdoor and semi-outdoor environments. He will be presenting a roundtable discussion entitled, "Digital Displays in Transportation Venues,” at Digital Signage Expo 2015 on Wednesday, March 12 from 12:30-1:30 p.m. at the Las Vegas Convention Center. For more information visit www.dse2015.com.