Road markings

[tomgwyther]

It's an idea which has been in my mind for years; the idea of using shiny gloss paint for road markings.

 

It's fresh in my mind again as recently, a friend of my mother was killed in a road accident because she could not see the road makings. The road in question is renowned for being an accident black-spot. It forms a sort of 'Y' shape, where people coming from the top-left of the 'Y' don't realise that they must give way to those coming from the top right. People crash into one another because they think they're just driving along a normal stretch of road with a slight bend in it, unaware that another vehicle is coming to hit them in the side.

 

Something I've noticed when driving in wet weather, especially when it's dark, or when the sun is low in the sky, is that you cannot clearly see road markings, most importantly on round-abouts and intersections. One thing I can see very clearly are the lines of glossy black tar which is used to seal joins in the road after road works. these lines show up very clearly and sometimes are themselves mistaken for road markings.

So, my question is this... Why not use high gloss paint for road markings?

Edited September 24, 2010 by tomgwyther

[Pangloss]

I'm not sure, and I think it's a great question. I wonder if the answer has something to do with contrast being more important than reflectivity, since the latter could cause reflections that distract and/or fail to convey the presence of the markings they cover. (But perhaps something more like a Fresnel lens might work, if such could be found in a liquid form.)

 

BTW, that's why they put down reflectors along with the paint. But I've always felt that reflectors are an imperfect solution to the "wetness" problem, since they seem to become damaged more quickly than paint wears out. And sometimes they don't use them, which I assume is a function of budget compared with traffic level on the road in question.

 

[Bignose]

BTW, that's why they put down reflectors along with the paint. But I've always felt that reflectors are an imperfect solution to the "wetness" problem, since they seem to become damaged more quickly than paint wears out. And sometimes they don't use them, which I assume is a function of budget compared with traffic level on the road in question.

 

Here in Iowa it snows enough that it isn't worth putting those down -- the plows just pry them up each winter and dig into the pavement where the reflector was. I do miss them from when I lived more in the south however, when it is nighttime and raining.

Edited September 25, 2010 by Bignose

[JohnB]

I think that the first question is "Why isn't there a "Give Way" or "Stop" sign on the top-left fork?" That would solve the problem.

 

I can't speak for others but we use a number of different paints down here. Yellow is only for "No Parking".

 

Road dividers are always a semi-gloss white, which can still be hard to see in the rain.

 

We also use a sort of white plastic paint which has crystals in it that make it highly reflective. First used for zebra crossings and stop and give way intersections, it's use is spreading to lane dividers as well now. Being a rather gluggy paint we also apply it with lumps about every 2 feet as a road edge marker. (Drifting onto it is quite noisy and wakes the driver up if he/she has started to drift off. Very effective.)

 

But to the OP, there should be a "Stop" or "Give Way" sign on every intersection not controlled by lights. We do it down here, even in the middle of nowhere, I see no reason Britain can't do the same.

[tomgwyther]

Not sure if there is a stop or give way sign on that particular intersection, the gloss paint idea wasn't specifically aim at that one place, more just roads in general. Cat's eyes work on straight road and in any case you can figure out where the middle of the road is. It's mostly roundabouts and intersections which pose a problem. you can even watch people following the black lines of tar rather than the white lines on some bits of road near me.

[StringJunky]

Not sure if there is a stop or give way sign on that particular intersection, the gloss paint idea wasn't specifically aim at that one place, more just roads in general. Cat's eyes work on straight road and in any case you can figure out where the middle of the road is. It's mostly roundabouts and intersections which pose a problem. you can even watch people following the black lines of tar rather than the white lines on some bits of road near me.

 

If your observation is correct then the scope of visibility in diverse conditions could be effectively increased if the depts responsible for roads ran a gloss black line alongside the white one improving safety....might be worth bouncing your idea off The Royal Society For The Prevention Of Accidents.

[tomgwyther]

i wasn't thinking specifically of running a gloss black line along side the traditional white line, rather combining the effects of it with the white line. that is: To have a Gloss white lines. I'd need to experiment with it.

I had a look round for a picture illustrating this but couldn't find one. next time i notice it, I'll take a picture with my phone maybe.

Good idea to take itup with The royal society for the prevention of accidents. I'll have a look at their website.

[swansont]

I recalled this thread the other morning when it was raining. The problem, as with the issue of having trouble seeing markings when it rains, is specular reflection vs diffuse reflection. Specular reflection what we're familiar with from Snell's law: the angle of incidence equals the angle of reflection. Diffuse reflection actually follows it as well but if the surface is not smooth, you have reflections in many angles and you can't keep track of it — the light goes in all possible directions. That's what happens with non-glossy surfaces.

 

But a glossy surface is going to give you something that is closer to specular reflection, , which means that the light from your headlights is going to bounce away from you, rather than back into your eye. It's also what happens when a rougher surface gets a relatively smooth covering of water — things look darker because much more light is scattered away from you instead of toward you. What you want is a nice reflective material but with a rough finish, so that some of the surfaces are always going to send light toward your eye.

 

Here's a link that goes into more detail, with pictures and all.

http://www.physicsclassroom.com/class/refln/u13l1d.cfm

 

It also mentions glare, which might be a problem with glossy paint — light from a driver going in the opposite direction could be an issue.

[StringJunky]

I recalled this thread the other morning when it was raining. The problem, as with the issue of having trouble seeing markings when it rains, is specular reflection vs diffuse reflection. Specular reflection what we're familiar with from Snell's law: the angle of incidence equals the angle of reflection. Diffuse reflection actually follows it as well but if the surface is not smooth, you have reflections in many angles and you can't keep track of it — the light goes in all possible directions. That's what happens with non-glossy surfaces.

 

But a glossy surface is going to give you something that is closer to specular reflection, , which means that the light from your headlights is going to bounce away from you, rather than back into your eye. It's also what happens when a rougher surface gets a relatively smooth covering of water — things look darker because much more light is scattered away from you instead of toward you. What you want is a nice reflective material but with a rough finish, so that some of the surfaces are always going to send light toward your eye.

 

Here's a link that goes into more detail, with pictures and all.

http://www.physicsclassroom.com/class/refln/u13l1d.cfm

 

It also mentions glare, which might be a problem with glossy paint — light from a driver going in the opposite direction could be an issue.

 

 

 

How about using a black formulation of the white road paint with the reflective bits in it...that might negate the glare? What you would get then is a broken up glossy surface.

Edited November 18, 2010 by StringJunky

[swansont]

How about using a black formulation of the white road paint with the reflective bits in it...that might negate the glare? What you would get then is a broken up glossy surface.

 

That might work, and I think I've read that some road paints have tiny glass beads in them for just that purpose. But as in any application, cost vs. benefit comes into play at some point.

[StringJunky]

The value of reflective beads for road safety is well understood it would seem and has been around since the 30's. I've seen a reflective coating manufacture (glass beads in it) suggest using it on black surfaces for artistic purposes but not on the road so far.

 

I found this quite educative with good close up photos:

 

http://www.virginiadot.org/business/resources/Materials/MCS_Study_Guides/bu-mat-PaveMarkCh2.pdf

 

Currently, the way they try and deal with visibility of the lines in wet conditions is to make the beads big enough to protrude above the water line but they are prone to snowplough damage if made too big.

Edited November 19, 2010 by StringJunky

[between3and26characterslon]

It's an idea which has been in my mind for years; the idea of using shiny gloss paint for road markings.

 

It's fresh in my mind again as recently, a friend of my mother was killed in a road accident because she could not see the road makings. The road in question is renowned for being an accident black-spot. It forms a sort of 'Y' shape, where people coming from the top-left of the 'Y' don't realise that they must give way to those coming from the top right. People crash into one another because they think they're just driving along a normal stretch of road with a slight bend in it, unaware that another vehicle is coming to hit them in the side.

 

Something I've noticed when driving in wet weather, especially when it's dark, or when the sun is low in the sky, is that you cannot clearly see road markings, most importantly on round-abouts and intersections. One thing I can see very clearly are the lines of glossy black tar which is used to seal joins in the road after road works. these lines show up very clearly and sometimes are themselves mistaken for road markings.

So, my question is this... Why not use high gloss paint for road markings?

 

There is so little friction on wet glossy lines that bikes can get trapped on them and end up going in whatever direction the lines go in, can't accelerate, can't brake and can't steer.

[CaptainPanic]

As mentioned above, it's important to have a diffuse reflection. A single light source must hit the marking, and reflect back to all directions (especially roughly 180 degrees back into the eyes of the driver).

 

I am not sure that the high gloss paint can be effective.

 

Here is some wikipedia reading material on the subject.

[TonyMcC]

tomgwyther said- (cat's eyes work on straight roads).

This is true although they also work on curves if some of the light from your headlamps hits them. They are constructed internally so that rays of light leave the cat's eyes parallel to the rays entering. Not much to do with the paint discussion but I thought it worth mentioning.

[MR. Science]

Well thats something your going to have to talk to your local state dmv about, and the reason they use what they use is becuase its very inexpensive, as most states are deep in the red, the newest editions to road dividers is the plastic(what I call giant bumper sticker like markers) that get under the skin of your tires when you pass them, these are excessively bright and are more than adequate for the road, so i think theres already a solution to your problem.

[Moontanman]

I know the paint they use now is very slippery when it wet, that makes it very dangerous to motorcycles that attempt to stop at cross walks. In wet weather the combination of oil sheen on the road and the paint is like ice, it's not too bad for cars but it can cause a motorcycle to slide down even if you are sitting still... maybe the more reflective the paint is the more slippery it becomes?

[Charlie]

I'm guessing it's to do with the grip of the tire on the glossy surface.

[John Cuthber]

As far as I can see, it's difficult to tell gloss paint from matte unless there is a small bright light source about the place somewhere.

This is England so the sun isn't a reliable answer. Your own car's headlights are pointing in the wrong direction.

I don't think glossy paint would help nearly as much as a signpost to warn drivers about the other road merging.