Adjusting acoustic signals and deciding: Whose road is it?

Some people find the sound of signals disturbing, especially at night. Many citizens from different municipalities demand the option of adjusting the volume of the signals. Prisma Teknik’s Pedestrian Signals provide just that to the elderly or visually challenged pedestrians – an automatic noise controlled environment in which volume can be moved higher or lower. It is the company’s proven technology since many years. It helps to activate sound changes & speech messages and adjust the volume of acoustic pedestrian signals. There are applications for special groups who need to activate “their” specific functions like speech messages to tell them where they are and provision to raise the volume and prolong the signal’s green period to cross the street safely. Acoustic signals are very helpful for such pedestrians. For example, a preschool pupil crossing a street to enter a playground needs extra green time to cross the street before the signal turns to “red” for other pedestrians. In Sweden, such pupils get “double green time” at special intersections when they use a tag with a security code.

Wireless sound activation from a remote unit is another feature of these interactive signals. The concept is simple. The visually challenged pedestrian uses a wrist strap with a receiver. When he approaches the intersection, the small remote in the strap begins to vibrate and beep. When he presses the button ‘nr 1’, the location tone in the APS unit gets started for the pedestrian giving him directions to find the push button and get further directions. The sound remains on during “green” (the walk phase) and stops after one cycle. Using button ‘nr 2’ on the remote unit, he can activate a speech message that gives him information about his whereabouts and the name of the crossing he is at.

The optimal solution is to have the sound on with locator tone 24 hours a day. Both normal sighted and visually impaired people need to be able to travel and explore new cities just like anybody else without extra remotes or smart phone applications to be able to cross the street safely. The signals don’t separate pedestrians with vision from vision impaired pedestrians. The challenge is to provide the visually impaired pedestrians with information and tools to walk safe on the streets.

Adjusting the Sound

In order to cross an intersection, we normally go through four steps using our eyes, ears and senses. This is clearly defined in several reports like the WPI report, “Accessible Pedestrian Signals Evaluating Pedestrian Signals For Visually Impaired Persons In Copenhagen” (2009).

But for a visually impaired person, these four steps get all the more emphasised as he needs to compensate for his lack of vision. The Prisma APS products support all the pedestrians to cross the roads safely based on this concept. These four steps are;

1. Locate intersection

The push button has a locator tone which sounds during the red phase (don’t walk phase). It helps the pedestrian locate the intersection and the correct crosswalk. The volume level is automatically controlled by the ambient noise.

2. Correct orientation

To help the pedestrian locate the direction of the crosswalk, there is a tactile arrow – with or without a vibrator – placed on either the top or the bottom cover. On the right side of the push-button there is a tactile map for the visually impaired to “feel” the intersection obstacles – number of lanes and also to know if there is an island or a tram.

3. Determining when to cross

When the traffic light changes from “red” (don’t walk) to “green” (walk), there is a distinct change in the sound – the most common is a change to faster frequency of the sound. The volume level is automatically controlled by the ambient noise.

4. Crossing the street safely

Following the sound from the opposite side, the pedestrian can now cross the street safely. The sound from the other side of the street gives direction to the pedestrian to walk straight at the zebra crossing. At large intersections, external speakers at the top of the pole are used to increase the sound during Green and flashing green (flashing red in some countries) colours.

This is the basic safety concept for pedestrians that needs to be implemented in many cities in all parts of the world. Even if the technology develops with new interesting products, these four steps will still be the basis of all of them.

As the technology develops, we can now see the next generation of pedestrian safety equipment. System interaction between different components in the traffic environment like emergency vehicles, buses, cars, traffic control systems and traffic monitoring systems get connected to control the traffic situation. These systems need information from all kind of sensors and equipment at the road side including the assessable pedestrian signals. The pedestrian push–button is a part of this infrastructure to provide information about the pedestrian and/or the exposed pedestrian (child, elder, week sighted) to the traffic control system.

The ITS systems will develop faster in the next 10 years from now compared with the last 10 years. Wireless solutions will become more common along with solar power solutions. Low power consumption is one of the most important demands developing new electronic products. We are supporting wireless connections from APS unit to traffic controller as soon as the traffic security approves the technology.

Marcus Lidhed

CEO, Prisma Teknik, Sweden

(Marcus Lidhed has 20 years of experience in the IT industry with specialisation in operating system development. He is with Prisma Teknik AB in Tibro, Sweden since 2009. The company drives the development of modern products for road safety for pedestrians.)