비오는 날 차선이 안보이는 이유가 

지금까지 뉴스에서 유리가루를 빼놓고 부실시공 한 탓이라고 보도하는 바람에 그런 줄 알았습니다.

그런데 아니네요.

Dry and wet retroreflective performance: glass beads

While glass beads still have lane-marking advantages, they are problematic during rain or when under water because they sometimes seem to disappear from the driver’s vantage point. The answer to the question about why pavement markings disappear in the rain is found in the physics of retroreflectivity and the index of refraction—as it relates to pavement markings, how light is bent when entering and exiting retroreflective media.

When properly embedded in a striping binder, glass beads under dry conditions redirect light back to its source, e.g. the driver with his or her headlights on. This is called retroreflection. The driver can see that the light appears to be coming from the striping. During rainy or foggy weather, the glass beads are covered in water, which makes non-ideal refractive index layers. This is like putting on the wrong pair of glasses and seeing things out of focus. Headlights bounce off the water surface and from the beads in many directions other than back to the driver, so the driver cannot see the striping. Consider how a straw in a water glass appears to bend to one side.

Nighttime color of pavement markings is also important. Standard glass beads are clear, so they depend on a colored binder to perform adequately. When using a yellow binder, they can appear washed-out at night.

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Pavement markings that use glass beads with a lower refractive index (RI) seem to “disappear” when wet because water presence causes the light to focus differently. Refractive Index (RI) interfaces define how much light bends (refracts.)

출처는 아래와 같습니다.

https://www.3m.com/3M/en_US/road-safety-us/resources/road-transportation-safety-center-blog/full-story/~/why-do-pavement-markings-disappear-in-the-rain/?storyid=90b6c8e2-1c04-4491-adc6-9df3e09f022d

유리가루 (Glass beads)가 들어간 경우, 물이 뭍으면 빛의 회절이 커져서 오히려 더 안 보이는건 당연한 거라고 합니다.

유리가루를 사용하는 것은 '맑은 날 야간'을 위한 것이지 비오는 날 밤을 위한건 아니였군요.

또한, 내구성의 문제도 있구요.

이러한 문제로 인한여 3M에서 대체물질(세라믹) 개발을 하는 모양인데, 가격이 비싸면 사용하지 않겠네요.

맑은날 밤에 잘보이면 부실시공은 아니구요, 비오는 날 안보이는건 당연한데, 공무원들과 시공업계에 계신분들이 과도하게 욕먹는 것 같습니다.

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추가 자료입니다.

Glass bead는 대충만드는게 아니라, 특정 높이, 거리에서 라이트의 반사가 최대 효율을 낼 수 있도록 만든다고 합니다. 운전자의 시선과 거리를 감안하는 거지요.

잘못된 형식의 이미지 링크입니다.

그런데, 젖은 노면을 위해서는 추가로 확보되야 하는 사항들이 있습니다.

우천시 차선의 시인성 확보를 위해서는 Profiled Marking시공을 하거나 Glass bead를 큰걸 사용하여 수분이 맺히는걸 방지해야 한답니다. 그리고 RI값이 작은 Beads를 써야하구요. 보통 길에서 차선이 두껍게 튀어나오도록 시공된 구간이 우천시에도 잘보이기는 합니다.

잘못된 형식의 이미지 링크입니다.

잘못된 형식의 이미지 링크입니다.

<Profiled Marking>

잘못된 형식의 이미지 링크입니다.

<Large Glass Beads>

Wet / Night Visibility In dry weather, traditional glass beads can provide excellent retroreflective visibility. During wet conditions, however, it can be beneficial to use beads and/or markings with special properties. This is to avoid a thin film of water on top of the road marking, which will deflect light from the vehicle headlights in various directions instead of reflecting it back. To enhance retroreflection during wet conditions, profiled markings and/or larger glass beads can be utilized to ensure the top of the beads are above the water film.
Beads with higher refractive index can also be used to direct the light more efficiently. A glass bead’s refractive Index defines the angle at which light is refracted within a bead, this bends the light towards the embedded part of the bead, which acts as a mirror and causes the light to be reflected back to the driver.
The specific refractive index is determined by the glass chemistry. Standard glass beads from reprocessed glass nominally have a 1.5 refractive index value which meets the European standard requirement EN 1423 and EN 1424. Higher refractive index beads are available and these can be used to improve the performance during wet conditions.

출처는 아래와 같습니다.

https://www.geveko-markings.com/fileadmin/root/common/pdf/brochures/UCme_R__Brochure_GB.pdf

https://www.driverknowledgetests.com/resources/what-are-raised-profile-line-markings-or-rumble-strips/

그러하다..