How to Specify Silicon Constellations Inc. LumiCrosswalk™

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1.0 Wireless Lighted Crosswalk Warning System

All in-roadway warning lights are affixed to a depression created in the road surface. The depression in the road surface varies in shape and size between different manufacturers and their light models. In case of the wireless lighted crosswalk, once the step of securing the lights into their road base is done, the entire installation is considered complete. In case of the hard-wired lighted crosswalk, one also has to route a multitude of buried electrical wires spanning the full length and width of the crosswalk.

Hard-wired crosswalk lighting systems are outdated for obvious reasons:

  1. The in-roadway lights require wired connections for power and communication. The electrical connectors used in this application have been known to fail due to incorrect installation, moisture ingress, corrosion, and mechanical stress. In some cases, failure of one connector causes malfunction of all subsequent lights in the wired chain.
  2. There are 200 linear feet of electrical wires in an average hard-wired lighted crosswalk installation. All of these wires typically lead back to the single controller cabinet situated on the side of the road. The wires are buried in the roadway by the means of trenching or saw cutting. This significantly increases the risk of permanent road surface degradation. The road surface is unnecessarily weakened and can crack or shift under the repetitive loading of heavy traffic. The shifting of the road surface tends to apply additional mechanical stress to the buried wires, often causing electrical circuit failure.
  3. These buried wires must be sealed and protected with epoxy, which leads to unsightly stains crisscrossing the entire crosswalk area.
  4. The additional labor for installation of the wires adds significant cost to the price of the system.
  5. The malfunctioning of individual lights or entire wired strings of lights is difficult to troubleshoot. The failure point in the wires may not be easy to find and repair. The long-term maintenance of hard-wired crosswalk lights can be expensive. While some of the system components might be covered by manufacturer’s warranty, the repair labor is typically the end user’s responsibility.
  6. Additional cost and time are required to secure the connection to the electrical utility grid. In many cases, electrical utility company also requires a separate cabinet for the electric power meter.
  7. In case of a solar powered hard-wired lighted crosswalk, the solar panel requirements are exacerbated. The entire system is powered by a single large solar panel. The rating of these solar panels is frequently 70 or more watts. The wind loading forces are directly proportional to the wattage and surface area of the solar panels. Therefore, they require extra large and tall mounting poles. The poles required are heavy, expensive, often more than 25 feet tall, and more than 6 inches in diameter. The concrete foundation and large pole requirements only make an already expensive system more costly.

The state of the art lighted crosswalk warning system consists of solar powered, wireless in-roadway lights (IRWL) and wireless controllers. The solar power and wireless control features together eliminate the need for trenching or saw cutting of the roadway. Each IRWL and wireless controller is self-powered by its own individual solar cell. The IRWL solar cell is embedded in its compact waterproof housing inside the road surface. The wireless controllers, one on each side of the road, require only a 10-watt solar panel. The distributed solar power approach alleviates the sizing requirements of their mounting poles. The standard traffic sign poles, only 12 feet tall and 3 inches in diameter, are reused for this purpose. Each IRWL and wireless controller contains a radio frequency circuit for remote control and bi-directional wireless communication. The self-contained wireless in-roadway lights are simply epoxied in the 5-inch diameter asphalt core. These unique advantages of the solar and wireless approach to lighted crosswalks are outlined in the U.S. Patent number 7,429,919.

Trenching or saw cutting of the roadway or sidewalk shall not be permitted. Electrical conduits inside the roadway or sidewalk shall not be permitted. Wires inside the roadway or sidewalk shall not be permitted. Solar panel size shall not exceed 20 watts per controller unit. The system shall be solar powered with rechargeable battery backup. Solar batteries shall maintain uninterrupted operation during cloudy periods for at least 30 days under normal use.

2.0 Wireless In-Roadway Lights

Pavement Intrusion Limitation

The most common type of the top road surface layer is asphalt concrete (A.C.) pavement. The damage to the roadway surface due to the coring or saw cutting shall be minimized. Every penetration of the road surface potentially creates a weakness zone. This can lead to accelerated fatigue cracking of the A.C. pavement. The weakness zone shall not propagate beyond the topcoat surface. Therefore some limits should be imposed on both the depth and the diameter of the core for IRWL installation. The thickness of the A.C. pavement layer varies depending on the Road Classification and Traffic Indices. The standards for industrial, commercial, and residential roadways call for A.C. pavement layer thickness of 3 inches. The LumiStar is the least invasive of all IRWL models in use at pedestrian crosswalks. The LumiStar light base has the smallest diameter and core depth of any IRWL currently in use in the United States.

  1. Depth

    Coring or saw cutting beyond the first asphalt layer shall not be allowed in order to minimize the risk of cracking and erosion of the underlying layers. The top layer of the roadway surface shall not be fully penetrated under any circumstance. The in-roadway light base shall not penetrate the roadway beyond 1.5 inches in depth.
  2. Diameter

    The surface area occupied by the in-roadway light is a discontinuity in the structural integrity of the roadway. The tire contact surface area is defined by the tire width, tire air pressure, and the wheel load. For an average tire, width is 10 inches, air pressure is 32 psi, and wheel load is 1000 lbs. This results in a tire contact area of 3.125 inches long by 10 inches wide. Ideally, most of the load from the vehicle tire should transfer directly to the asphalt. Therefore the diameter of the IRWL core should kept to a minimum or no more than half of the tire width. The core diameter for IRWL installation shall not be greater than 5 inches. The in-roadway light base diameter shall not exceed 4.75 inches.

In-Roadway Lighting Light Snowplow Resistant Base - IronStar

For snowplow resistant installations this specification replaces the normal base specification: The in-roadway light base shall not penetrate the roadway pavement beyond 1.70 inches in depth. The in-roadway light base diameter shall not exceed 8.80 inches. The snowplow resistant base shall contain the removable shield manufactured from heat treatment hardened 17-4PH stainless steel. The shield shall be replaceable without the need for coring or saw cutting of the roadway. The shield shall be secured to the anchor with eight tamper resistant screws.

Visibility And Brightness

The IRWL LED lamps shall be located above the road surface. The location of the LED lamps above road surface is a key factor in the prevention of dirt buildup in the areas where the light is emitting from the fixture. Certain competing solutions claim IRWL installation flush with the grade. This means that the LED lens is located in a depression below the grade where dirt and debris tend to fall and collect. Some roadways are kept cleaner than others depending on the cleaning schedule and nature of the surrounding terrain. Therefore, for maximum visibility it is advantageous to keep the light emitting surfaces above the road surface.

Flush mounted in-roadway warning lights shall not be permitted.

The in-roadway light geometry shall be designed such that dirt, dust, and debris will not accumulate in front of the LED lenses.

The in-roadway lights shall be light emitting diode (LED) type.

The amber LEDs shall emit light at a wavelength of 590 nanometers.

The luminance of each IRWL LED shall be a minimum of 4,000,000 cd/m2.

LED visibility distance shall be at least 2,000 feet on a sunny day.

The LED protective windows shall be designed such that direct contact with vehicle tires is not possible.

Durability And Toughness

Inside the wireless IRWL waterproof enclosure are light emitting diodes (LED), light focusing optics, solar cells rechargeable battery, and electronics circuit boards. All of the internal components must be fully protected from dust, rain, and mechanical stress.

External power connections shall not be permitted.

The in-roadway light housing shall be made of 17-4PH stainless steel.

The light fixture housing materials shall withstand repetitive ASHTO HS-20 vehicular loading without sustaining deformation or cracking.

The LED housing shall be fully O-ring sealed to prevent moisture ingress. The ingress protection rating shall be IP 68.

The in-roadway light shall be attached to its base with stainless steel screws ¼–20, 1.5” long.

Each in-roadway light shall have its own solar battery unit.

Each in-roadway light shall have its own wireless controller.

3.0 Wireless Controller

Wireless controller shall be triggered by pedestrian push button or IR bollard system. Wireless controller shall activate all associated in-roadway lights, LED enhanced crosswalk signs, and flashing beacons within 1,000 feet (line of sight) distance. The wireless signal transmission shall ensure synchronized activation of all crosswalk-warning devices. Wireless controller shall operate within 2.4 GHz FCC approved license-free spectrum. Wireless controller shall not interfere with other installations. A waterproof fiberglass enclosure shall be provided. The enclosure shall meet or exceed NEMA 4X rating. The controller enclosure size shall not exceed 8 inch (height), 6 inch (width), 4 inch (depth).

4.0 Wireless LED Enhanced Signs

LED enhanced signs shall be self-contained. The LEDs, wireless controller, rechargeable battery, and solar charger circuit shall be enclosed in one low profile, sign shaped, housing. The sign housing shall be waterproof. Vandalism and aesthetics should be taken into consideration of the LED sign construction. The self contained LED sign should be designed to appear like its normal passive sign equivalent. The depth of the sign housing should not exceed 1.4”. Separate or additional enclosures for batteries or electronics shall not be permitted.

W11-2 (24 inch size)

Sign face shall be Federal Designated Type W11-2, fluorescent yellow-green (FYG) color.
Sign face shall be LED-enhanced using 8 amber LEDs.

W11-2 (30 and 36 inch size)

Sign face shall be Federal Designated Type W11-2, fluorescent yellow-green (FYG) color.
Sign face shall be LED-enhanced using 16 amber LEDs.


Sign face shall be Federal Designated Type S1-1, fluorescent yellow-green (FYG) color.
Sign face shall be LED-enhanced using 8 amber LEDs.


Sign face shall be Federal Designated Type R1-1, red color.
Sign face shall be LED-enhanced using 8 red LEDs.


Sign face shall be Federal Designated Type R10-15.
Sign face shall be LED-enhanced using 8 red LEDs.

The sign LEDs shall be wirelessly flash synchronized with all other wireless crosswalk system lights.

Total luminance from the sign face shall be a minimum of 4.5 million cd/m2. The LED lights shall be visible in full daylight from a distance of at least 4,000 feet.

Pedestrian crossing sign shall contain a wireless radio frequency controller. The wireless signal range of the built-in controller shall be at least 1,000 feet (line of sight). The wireless controller shall be integrated into the sign enclosure and operate in the 2.4 GHz license free ISM band.

5.0 Wireless Communications

The system shall be wirelessly accessible with information data retrieval capability.

The IRWL shall be wirelessly configurable for flash frequency, flashing duration and flashing duty cycle.

The wireless controllers and in-roadway lights shall be based on a high-speed embedded micro-controller with radio interface and shall include system operation software with user adjustable parameters accessed wirelessly via a portable computer.

6.0 Warranty

All system components shall be covered under normal use by a 5-year manufacturer’s warranty.

7.0 Manufacturer Proof of Insurance

The manufacturer shall provide the purchasing agency with “Proof of Product Liability” Insurance covering “In-Roadway Warning Lights” for use at crosswalks.