A long time ago, there was a person aboard the buses whose role was double: ensure that all people had paid the tickets and announce the next stop. The second role was important, especially for people new to the respective bus line. Today, this is no longer necessary. More and more buses are equipped with Passenger Information Systems (PIS) that do the job in a much more effective way. But what is such a system ?
The beginning of PIS
The first generation of information systems used loud speakers. Prerecorded messages were played when required. This was the first step towards an automated PIS. Passengers wanted just to know when to get off the bus or subway, especially when it was crowded and visual contact with the surrounding environment was not possible.
The PIS today
A PIS is a device mounted overhead, just under the ceiling of the bus. There are two places were most of the PIS are installed: the front of the bus and the middle of the bus. There are other places where it can be placed, but the vast majority of the buses with such a device use the front or the middle position.
The front-mounted PIS
The front position is close to the driver. The natural position of the people traveling in the bus is towards the front, The seated passengers are facing the PIS anyway. The standing passengers are distributed randomly, but the longitudinal placement of the handles and bars make them face the front in most of the cases. It is very comfortable to look at a display with 10 cm letters placed at 3 to 8 meters.
The central PIS
The other choice is the middle position. This is a good choice, too. Passengers that enter the front door of the bus have a natural tendency to face the rear of it. The display panel is double sided. People that face the front of the bus can still read the PIS. A bus having both a front and a middle PIS would look as the ideal choice. One of the advantages of the middle PIS over the front one is the width of the panel. In buses with a driver cabin, placing the PIS at the front can limit the width. For the people in the back, in window seats, there can be difficult to read the display. The middle PIS has the advantage of a much wider field of view, plus a good reading distance.
The PIS in subways and trains
In the case of subways, the double-sided PIS is installed in every car, at regular intervals. The device is much larger than the bus version. Most of the subway cars have flat ceilings and the PIS can most of the time stretch over more than a full 2m span. The greater PIS can have additional information, like flashing arrows indicating the side which the doors will open at.
For a subway car, the LED display can sometimes have a TV display variant, depending on the height of the ceiling. This has the advantage of being able to present more information. There is a drawback, too. The small letters can limit the distance at which the PIS is readable. In some cases, the TV screens are mounted sideways, near the doors. This is useful for narrower cars, but requires many such displays, according to the number of doors.
According to Guo, Huang, Huang, and Juras, the PIS can communicate by using different technologies, among which we find mobile and Bluetooth. There are advantages and drawbacks for each technology. We will consider the two candidates mentioned above.
The mobile networks develop at tremendous speeds. 2G, 3G, 4G are already in place. 5G is no longer a dream. They have high data rates and they have become world standards. Machine to machine systems, based on 2G are ideal for low to moderate speeds, which the PIS need. unorthodox telecom operators using exotic technologies like Ultra Narrow Band or LoRA have re-invented the world of industrial communications. The mobile-based PIS can be controlled either by the computer of the bus or from the headquarters of the public transportation company.
For places where mobile coverage is an issue, there comes Bluetooth. This low-range technology is great when it comes to local data reliability. The computer of the bus communicates with the device via wireless channels and the driver can insert custom messages depending on the needs of the moment.
We can mention the PIS connected through wires. It is the firt generation of PIS and there are many buses or subways that use this old technology. Once put in place, the PIS is hard to change, sometimes requiring many hours of manual work.
More and more PIS combine the visual information with audio messages. We are talking about an enhanced version of PIS. In crowded spaces, direct line of sight may prevent people from seeing the screen. In such cases, audio comes to the rescue. Also, in loud environments, the message cannot be heard, but the visual one is still available.