A little girl placing a call at an accessible pedestrian signal



Accessible pedestrian signals (APS) are devices that communicate information about the walk and don’t walk intervals at signalized intersections in non-visual formats to pedestrians who are blind or who have low vision”. Accessible pedestrian signals play a crucial role in ensuring safety and accessibility for all individuals, primarily those with disabilities. As cities strive to enhance their infrastructure and comply with the 2023 PROWAG guidelines, the two main types of APS may be difficult to navigate. Independent APS and networked APS have many similarities but also a few vital differences. While both aim to facilitate pedestrian navigation, they do so through different mechanisms, each with its own set of advantages and limitations. By delving into the nuances of these two systems one can better understand their similarities and differences enabling one to make an educated decision about which is better for any intersection one may come across.


What Makes a Push Button and Accessible Pedestrian Signal?

to be considered an APS system, the system must provide pedestrians with audible, visual, and tactile information about the walk and don’t walk phases. Audible information from an APS consists of two different types depending on the distance your buttons are apart from one another at the corner of the intersection: verbal messages which can include notifications such as “wait to cross Broadway at First St.” or “walk sign is on to cross Broadway”, and tones which are standard percussive tones equated to each verbal message.


Independent APS

As an APS system, independent APS provides pedestrians with audible, visual, and tactile indications and is referred to as an independent system due to the lack of equipment in the traffic cabinet. Independent APS is often referred to as a 4-wire system as 4 wires connect from the pedestrian signal head to the button itself. For a fully actuated intersection, an independent APS utilizes two field wires from the button to the traffic control cabinet to place calls.

With PedSafety’s Guardian® lineup of independent APS systems, an APS is provided with power and indications from the pedestrian signal head through SPI (Signal Power Interface). Within the button itself is where all the main information is stored such as data storage, settings, configurations, etc. and the SPI is housed within the pedestrian signal head, routing signal status back to the button. Each APS has a 1 to 1 relationship between the pedestrian signal head and the APS itself.


Networked APS

On the contrary, networked Accessible Pedestrian Signals (APS) systems offer significantly more flexibility in intersection setup. Often referred to as 2 wire systems, networked APS systems incorporate all the essential APS functionalities while enabling integration into an agency’s network for remote monitoring, troubleshooting, and adjustments.

As a networked APS system, the intersection is designed to allow remote configuration and monitoring. Due to its architecture, the networked system can control up to 16 buttons at the intersection across 8 different pedestrian phases, making it particularly suitable for large or complex intersections. With fewer wires attached to the button compared to an independent APS, all logic is stored in the controller within the cabinet (which can be either a card rack or shelf mount). Additionally, the system can be powered through field wires, SPI, or solar power, offering extensive customization options.

PedSafety’s WiAAPS® range of networked APS systems are 2-wire systems powered by the existing two field wires. In situations where field wires are non-accessible, WiAAPS® can be powered without any field wires through an SPI in the pedestrian signal head or by using solar power, eliminating the need for any wires to run back to the traffic control cabinet. WiAAPS® consists of the WiAPC/WiAPC-C (controller) and the WiAPB (push button). The WiAPC/WiAPC-C maintains continuous communication with each WiAPB within a network-based control system that operates wirelessly through secure 900MHz narrow-band communication. Users benefit from both safety and security, as well as reliability, with the WiAAPS®’ mesh network protocol.


Which is a Better Choice?

When comparing independent and networked APS systems, the key distinction lies in the remote networking capabilities offered by networked APS. The ability to remotely monitor button status and make system adjustments is invaluable. networked APS can integrate smoothly into existing intersections, whether or not field wires are present, without compromising the ability to activate an APS call. The fact that networked APS can be installed without the need for new wiring is particularly significant when upgrading older intersections to include APS.

On the other hand, an independent APS fulfills all the essential requirements of an APS system but derives its signals directly from the pedestrian signal head instead of the traffic control cabinet, allowing for quick installations. This approach reduces costs for the agency and offers a simpler product that does not add additional equipment to the already crowded cabinet. For intersections with pedestrian phases on recall, an independent APS is an ideal solution, providing visually impaired pedestrians with necessary audible and tactile cues without requiring communication with the cabinet.

In summary, both Networked and Independent APS systems have their roles at intersections. If your focus is on networking capabilities within the cabinet or you need to retrofit an older intersection without digging up the street for new field wires, WiAAPS® is the ideal solution. Conversely, if budget constraints are a concern or you have intersections on recall that still require audible and tactile indications for the visually impaired, the Guardian® is the appropriate choice.



In conclusion, while both independent and networked accessible pedestrian signals serve to enhance safety and accessibility at intersections, they differ in their operational mechanisms and adaptability. Independent APS offers simplicity and a direct 1-to-1 relationship between the pedestrian signal head and the APS itself. In contrast, networked APS systems provide greater adaptability, allow for remote configuration and monitoring, and can provide the ability to place calls with or without field wires.

Ultimately, the decision between independent and networked APS depends on factors such as intersection setup, budget considerations, and the need for future adaptability. By carefully considering these factors, stakeholders can ensure the effective implementation of APS to improve pedestrian safety and accessibility in urban environments. For more information on the intricacies between the two systems, contact our sales team or your local distributor.