the pavement, or specially designed markers are used which include a protective metal casting that is embedded in recesses in the pavement, allowing the marker to protrude slightly above the pavement surface for increased visibility, much like a cat's eye. Lit LED in-pavement Raised Pavement Markings (RPMs), help improve road safety, as they are more generally visible than reflective RPM markings as they are internally lit and don’t require headlights to show up. And, whilst the RPMs are usually raised, being so visible, in snowplow areas, these types of RPMs can be installed flush-mounted within the pavement so that they completely avoid the snowplows. There are a number of types, ranging from a single LED point source RPMs, with limited daytime visibilities, (road studs), to multi-LED linear type RPMs, visible in all full sunlight and nighttime applications. Some lit RPMs can be visible and useful in both bright sunlight as well as nighttime applications, whilst others are only visible at nighttime or in low light applications. One of the key differences between these types is that lit linear RPMs, being linear, each lit unit provides both positional and directional guidance to viewers. For single-point source viewer directional guidance, a number of these units must all be viewed at the same time. In severe weather, such as fog or snow whiteouts, this may not be possible. Therefore, as each linear visual aid provides both positional and directional guidance, this type is more helpful as in a wider variety of weather conditions and light conditions. Some lit linear visual aids / RPMs, melt snow, without needing any additional heating elements, as such, these types or self-cleaning RPMs are more energy-efficient compared to those that need additional heating elements to melt snow so are NOT self-cleaning. Linear visual aids are also more useful since they can be used for creating in-pavement signs and messages such as lit merge arrows. Whilst point source RPMs could be used for such signage, in practice, because they are installed so close together and much deeper within the pavement compared to linear RPMs, such usage would tend to damage the road, especially within the asphalt roads. Usage of color in Europe In almost all European countries, such markers will include reflective lenses of some kind. Most appear white or gray during daylight; the colors discussed here are the color of light they reflect. Because of their inconspicuousness during