Monday, February 07, 2011

Last one on the roads can turn off the lights

In a head-scratching move some counties have decided to switch off the lights on sections of the motorway at off-peak hours; or in some instances reduce the light levels on non-motorway stretches at the same time. All part of the 'must save money' mentality. The other cost -

“On urban main roads, with mainly a traffic function, a reduction in accidents involving injuries of approximately 30% can be expected at night following an improvement in the lighting from very bad to good”
Admittedly that's from very bad to good and not the other way around, but one can infer a possible connection.

Now I moan and rant about the road network a lot, I'm sorry, but I hope that when I do so I offer suggestions that in my own opinion might be beneficial - I do try to be constructive. With that in mind...

It would be easy to simply declare those that work on our roads as idiots or morons; they're not - what does seem to be the problem is a reluctance to utilise new technologies on the roads themselves and I suspect that's down to budgetary constraints imposed upon them.

Take a look at a road - a new motorway for instance. In terms of innovation we have road markings, street lighting and cat's eyes (if you're very lucky the ultra high tech coloured cat's eyes.... woo advanced!) other than that it's pretty much remained the same for about 100 years. What are these improvements for and how do they work?

To begin a small diversion is required into the nature of light - light is generated by a source 'hits' an object and is reflected; if the reflected path intersects our eyes we get to see the object. As we want to be able to see the road it would at first glance make sense if it were reflective. However said surface also needs to operate during daylight and too reflective means too much light and dazzle. Therefore against common sense the road surface needs to be dull.

Making the road dull however throws up the problem that it can't be seen in low light conditions; sure you have headlights on a car but consider the path taken by the light. The light comes from your direction, hits the road and is reflected away from you. As such the road can't be smooth it has to be rough to allow some of the light to scatter back to the source.

As an aid to this we have cat's eyes that are designed to reflect light back; to an extent we also have road markings painted white to throw back some of that light and on some stretches street lighting to produce an ambient multi-reflectional source on the road.

Hopefully from this it can be seen that in order to keep dazzle low during the day something needs to be done to allow the road to be seen at night. To that end I make these suggestions -

Mica chipped kerb stones. A white line down the edge is fine but it shares the gutter which gets muddy. Combine that with kerb stones and any pavements being only a minor shade difference in colour to the road surface and it disappears at night. 'Glittery' kerbs won't produce much dazzle during the day but due to the scattered nature of the mica chips embedded will reflect headlights back towards the vehicle.

Cat's eyes. They're great and it's taken long enough to redesign them so they're both self-cleaning (without having to run over them) and in colours. The flaw lies in their placement in the middle of the road it works provided there's no other vehicle coming the other way and that they're clean enough to be seen. Instead of a painted white line divider (which gets worn away anyway) embed a set of low angle reflectors down the middle of the road. Repeat using coloured ones at every junction - a junction you can pull into green an exit red. This has already been done in places, but it needs to become more wide-spread.

Street lights - the biggy. Some activists are happy about the proposed switch off due to light pollution however this is a case of cutting off one's nose to spite one's face. What is required is tighter lights. Recall that light reflects from the road surface. Fit a street light directly above a road and point it straight down and the majority of light will reflect straight back up again; not only is this bad in terms of 'pollution' but it doesn't help the users of the road. So double-headed blinkered angle lights such that the majority of light falls at an angle on the road. With more light going in the right direction intensity can be reduced which cuts back on pollution both light and energy generation related.

Slightly off the topic from lighting - porous roads. Water forming on their surface is the best demonstration of why we don't want reflective road surfaces. Porous road surfaces exist they're just expensive

So there we have it - mica kerbs, cat's eye sets and angled lights. Short term expense for long term gain that would not only make our roads safer, but could reduce the energy costs on lighting.