1. Field of the Invention
The invention relates to pedestrian warning devices, particularly those that are incorporated into roadway corners or sidewalks for pedestrian use.
2. Discussion of Background Information
Sidewalks are well known structures that provide a walking surface for pedestrians, and that are frequently used on the sides of roads, parking lots, and other similar areas where pedestrians and vehicles are both routinely present. Such sidewalks are typically made from a form of pavement and are typically anywhere from 4 to 8 inches above the road surface.
To make sidewalks safer, particularly for users with disabilities, ramps are used to create a sloped transition from the sidewalk to the road surface. These ramps and associated landings are subject to numerous government regulations, particularly under the Americans with Disabilities Act, that are intended to ensure that the surface is safe for use by pedestrians and disabled persons.
In general, these ramps or landings have a concrete base, similar to the sidewalk itself, that is covered with a tactile panel, such as the Universal Radius Tactile Warning Surface Product (U.S. Pat. No. 9,365,985 B2), which is a glass and carbon composite panel that is enhanced with fiberglass truncated domes. Traditionally, tactile panels are either cast-in-place or surface applied.
Although cast-in-place tactile panels are easy to install in fresh concrete, they are difficult and costly to replace because once the concrete is set, the underlying substrate must be at least partially destroyed in order to remove and replace the tactile panel. One variation of cast-in-place tactile panels features spaced honeycomb-like lower walls. However, because of the nature of the honeycomb, air can become trapped between the lower walls, creating areas that lack support from the underlying substrate. This trapped air can result in a lack of support that can lead to fatigue, and cracking failure of the tactile panel due to repetitive and heavy loading.
Surface applied tactile panels are tactile panels applied to a finished substrate. Surface applied tactile panels are typically mechanically fastened and adhered to the underlying substrate. In addition, in order to compensate for irregularities in the substrate and minimize water intrusion that would otherwise damage the tactile panel, the surface applied tactile panels require additional caulking around the perimeter. Because surface applied tactile panels are mechanically fastened, they are easier and cheaper to remove than cast-in-place tactile panels. Once the fasteners are removed, the panel is heated to break the adhesive bond then stripped away from the underlying substrate. As a result, the underlying substrate remains intact, reducing the cost and time associated with replacing the tactile panel.
Although the surface applied tactile panel improves upon the cast-in-place tactile panel, both cast-in-place and surface applied tactile panels suffer from similar shortcomings. Both fail to remove the potential for air and water infiltration, which in turn compromises the structural integrity and functionality of the tactile panels.
These shortcomings are particularly problematic because the intersections of pedestrian ramps and sidewalks and street gutters are often locations where it is difficult to drain away standing water that remains after a rain or snow-melt event. Frequently there is insufficient pitch in these areas to provide positive drainage relief and puddles and ice may form resulting in hazards to pedestrians. If water is able to enter around the tactile panel at such a location or between the panel and the concrete slab, over time it will expand or contract, thus causing numerous problems to the long-term safety and stability of the ramp. To address these issues, ramp manufacturers go to great lengths to create water-tight or water-resistant tactile panels to prevent water from entering the ramp system. However, with a water tight ramp, pools of standing water may form at the base of the ramp during times of rain or melting snow or ice, causing puddles to form in the roadways and often back up the ramp, thus introducing a new hazard.
Porous concrete, also known as porous pavement, is distinguishable from traditional or non-porous concrete due to its high porosity, which allows for stormwater to infiltrate back into the ground naturally by passing directly through the concrete. Porous concrete has the ability to reduce pavement runoff and prevent pooling in areas that lack adequate drainage. As a result, porous concrete slabs allow water, whether the water comes from rain, melting snow or ice, or general road cleaning activities, to drain through the porous concrete and infiltrate back into the ground. However, current tactile panels do not allow water flow, thereby negating the benefits of using porous concrete as an underlying substrate.
What is needed, therefore, is a tactile warning device that is able to reduce the pooling or collection of water on or around the ramp and does not suffer structural degradation due to air and water infiltration.