Polara’s Wireless Pedestrian System, or WPS, is a solar-powered surface-mount ped pole with a wireless connection to a control unit in the pedestrian signal head, allowing accessible pedestrian signals (APS) to quickly and easily be retrofit into existing intersections. The WPS bolts to the existing sidewalk and does not need any wires for power or data, avoiding the need for excavation for foundations or wiring.
APS provides pedestrian signal information in audio and tactile form to people with vision disabilities. APS are a vital part of ADA-compliant accessible crosswalks, and should be placed near the crosswalk they serve to reduce confusion and aid blind pedestrians in finding and remaining in the appropriate crossing. The WPS makes compliant APS placement much simpler and more cost effective compared to traditional pedestrian poles.
In our recent WPS webinar, Ryan fielded many questions about the operation of the WPS. In this article, we’ve invited him to expand on some of his answers.
Q: What obstacles did you face in developing the WPS?
A: One of the challenges we had was the variability in traffic/pedestrian timing. For the WPS, how much of the day the APS button is idling in the Don’t Walk interval versus when it has been activated by a pedestrian and goes into the Walk interval affects the WPS’s power use.
Some “pretimed” intersections, where the Walk interval is baked into the signal timing and pressing the crosswalk button only activates the APS features, might have dozens of Walk intervals per hour. Other intersections might have only a handful of Walk intervals per hour. These cycles of interval changes have an impact on power consumption, which affects the size of the photovoltaics (solar panels) chosen and the battery capacity. As you can imagine, different sized solar panels and battery capacities could be paired together in many combinations, but this starts to become difficult for an agency to evaluate during planning and purchasing. Other factors that change from location to location and affect the choice of solar panel and battery include the amount of available sunlight, how long the system should work without sunlight, and a shading factor, which relates to how much of the available sunlight makes it to the solar panel. We decided to simplify the system and offer a single combination that would work in most locations.
Q: Have there been any problems with solar applications in larger cities with tall buildings and prolonged subzero temperatures?
A: Customers are experienced with solar in other applications and are accustomed to selecting sites well-suited for solar. Even in areas with tall buildings or low temperatures, the solar panel is sized to perform with limited light shining on the panels.
Q: Why was Bluetooth chosen over other wireless communication methods like Wi-Fi? What version of Bluetooth is being used, and is there a reason behind choosing this version vs others?
A: We chose Bluetooth LE (LE: Low Energy) for several reasons:
- Mobile devices (cell phones) have Bluetooth LE integrated, so using this technology allows installers and technicians to easily setup and configure the components of WPS without specialized hardware.
- Our existing iNS APS platform uses Bluetooth LE, so this choice gives customers a familiar experience and allows them to use the same Field Service App for iOS and Android that they already use.
- Bluetooth LE makes it simple to create a secured connection between devices, while other technologies require extra steps and can be more cumbersome.
Q: Is a Bluetooth connection secure? Isn’t it exposed to the public?
A: Bluetooth LE is secured. Upon initial setup, the two wireless components of the WPS (the WPC control board in the ped head and the Pedestrian Relay Module in the solar kit on the pole) exchange private, secured, digital keys, which are used for all further communication exchanges. The devices are also password protected. These mechanisms ensure that the WPS is only communicating the appropriate traffic information to the appropriate devices.
Q: Can the WPS crosswalk button send a call straight to the cabinet instead of to the nearest signal head?
A: We decided to limit the WPS wireless communications to a single corner of an intersection, not across streets or directly to the traffic cabinet.
The main use case for WPS is to install an APS button near a crosswalk where a pole and wires don’t exist. This is often the case for older downtown areas. Many downtown areas are pretimed, so there are no calls to place with the cabinet; but the pedestrian signal lamps are still receiving Walk interval timing from the cabinet. The WPC in the signal head communicates timing to the Pedestrian Relay Module in the solar kit on the same corner of the intersection, making a wireless connection over a much shorter distance than if we were sending a signal all the way to the cabinet.
At “actuated” intersections, where the crosswalk buttons are used by pedestrians to call for Walk intervals, there will likely already be button wires running to each corner of the intersection. The WPC can connect to those wires, allowing the system to place calls and recognize calls placed on each traffic phase.
Q: Have tree limbs/leaves or other infrastructure posed problems with obtaining wireless line of sight/connectivity?
A: This has not been an issue so far because the areas near pedestrian signal heads and crosswalks are usually cleared for pedestrians. Still, it is important to make sure the solar panel receives enough sunlight and that there is clear line-of-sight between the antennas for communication. It may be necessary to clear overgrown limbs for best performance.
Q: What happens when communications go down while a pedestrian is crossing? What fail-safe procedures does the WPS have?
A: If communications are interrupted during a Walk cycle, while pedestrians may be crossing, the system will return to playing the locate tone. This tells the pedestrian that they should make their way out of the crossing. Additionally, when button wires are available and wired into the system, the system will lock in calls to request the next Walk cycle.
