Polara offers two versions of APS, each with unique installations and benefits. Here, we explain some of the key differences to help you select the one that’s right for your intersection.
Intersections with crosswalks and pedestrian signals typically time the Walk signals in one of two ways.
At pre-timed intersections, the pedestrian Walk interval coincides with the Green light for the parallel traffic lanes. Every crosswalk gets a Walk interval every cycle of the traffic signals. Many older downtowns are set up this way. At these intersections, crosswalk buttons are either inactive or not installed.
At actuated intersections, the traffic signals cycle without pedestrian intervals until someone presses a crosswalk button calling for a “Walk” signal at that crossing. This arrangement has wires going between each button and the traffic cabinet to allow the buttons to place calls.
At their simplest, crosswalk buttons are momentary switches; power only flows while contact is made. Some buttons have “latching” pilot lights that, once pressed, stay lit until the Walk interval; these have more complex power needs.
Accessible pedestrian signals (APS) require constant power for the locator tone and audible indications. To accurately mirror the visual Walk/Don’t Walk signals, APS connect to the cabinet for signal timing; and at actuated intersections, APS also connect to the cabinet to be able to place calls, just like the crosswalk buttons they replace.
What is an APS? [Article link] >>>
When APS are added to an existing intersection, or retrofit, these connections must either be made through existing wires or new cables must be added; a challenge at intersections with conduit that is damaged or already at capacity.
To solve this, we design our APS to operate in either of two modes: 2-wire or 3-wire.
In 2-wire operation, our APS installs directly on the button wires – a two-conductor cable. Through our exclusive protocol, we transmit both power and data over the button wires to a controller in the cabinet; either an iCCU-S2 on a shelf, or an iCCU-C2 in a card slot. This is ideal for actuated intersections, where these wires already exist.
In 3-wire operation, our APS receives power and signal timing from an iPHCU3S control card in the pedestrian signal head, piggybacking off the wires to the signal lamp. This allows these APS to operate in pre-timed intersections where no button wires exist without running new wires to the cabinet.
Our iDS2 and iNS2 models are capable of either 2-wire or 3-wire operation; the iDS3 and iNS3 models are specifically 3-wire systems.
Benefits of 2-wire systems
2-wire APS are simpler to install, often replacing the existing buttons directly. By using existing wires and requiring only one control unit, this is a cost-effective and quick way to retrofit APS. Putting the control unit in the cabinet eliminates the need for a bucket truck and reduces the number of components needed.
Polara’s 2-wire APS use this connection to the cabinet for a range of other functions, including automatic sound synchronization; false-walk detection; emergency vehicle, rail, and transit preemption; remote monitoring; and system alerts.
This connection to the cabinet and its network link also allows agencies to remotely update their 2-wire APS firmware with Polara Updater – a powerful free utility for bulk remote firmware management.
Video: What is Polara Updater, and how does it simplify firmware updates?
Benefits of 3-wire systems
At intersections where the button wires are damaged or degraded to the point where they cannot be used, or where button wires were never installed, 3-wire APS are still capable of operation. Each APS connects to a control unit installed in the corresponding pedestrian signal head with a 3-conductor cable. The typically short distance between the signal head and the APS allows this cable to be installed inexpensively.
3-wire systems are ideal for adding APS to intersections with only 1-3 crossings or for pre-timed intersections. Since each 3-wire APS is a stand-alone unit with nothing in the cabinet, some features of 2-wire APS are unavailable at these crossings, such as preemption and remote monitoring.
Uniquely, Polara’s 3-wire APS offers wireless sync between APS on the same crossing. With this feature, activating one unit activates synchronized Walk and Clearance sounds on the linked unit.
The point
With the uniquely flexible operation of the iDS series, Polara’s APS works at both pre-timed and actuated intersections, giving agencies more options.
This article focuses on the differences between Polara’s two- and three-wire systems, but they share the same platform; a rugged case, quality components, secure wireless programming, and compatibility with both our Field Service App and PedApp®. All models in the iDS series offer cities a durable, reliable, and flexible solution for making pedestrian crossings accessible to everyone.