[thedoc (OP)]

ron walsh asked the Naked Scientists:
   
Would it be cost effective and safe if we lined roads with fluorescent grass?

I see all these articles where animals are getting fluorescent genes implanted into them and i cant help but wonder why we don't do that with grass to serve a real immediate purpose?

I've just read that astronomers estimate that in the UK alone, wasted electricity from street lights emits carbon dioxide equivalent to an extra 160,000 cars on the road each year. wouldn't replacing street lamps be a great use of fluorescent grass assuming it would bright enough?

I imagine that this could have an adverse effect on the ecosystem if it were used all over the place, but carefully sterilized fluorescent grass lining roads seems like a no-brainer to me.

What do you think?

[RD]

Would need to be bioluminescent rather than fluorescent to glow at night.

[alancalverd]

Getting rid of street lights on motorways would be a great improvement in safety at no cost. In fog or rain, the scattered light from overhead lamps actually reduces the conspicuity of vehicles.

Replacing the crash barriers with wild roses would be a good idea. Unlike wire ropes or steel bars, they absorb energy and don't shunt the vehicle back into the traffic flow.

Luminescent plants, whether grass or thorn bushes,  would make the road edges as conspicuous as safety jackets and hi-viz signage.   

[CliffordK]

Street lights do light up a greater area than one's headlights.  The concern is not running into other cars (which have headlights on), but rather running into unexpected stuff like animals or people on the roads.

As far as the bioluminescent plants.  Undoubtedly they would not follow the road contours closely enough.  So, there would be places where the road would turn, but the plants would not appear to turn.  For example, when the side of the road is a cliff face.

Grasses tend to spread, although perhaps one could develop sterile second generation seeds.

[evan_au]

There is already a project aiming to develop glowing trees to replace streetlights.

Many of the experiments with glowing mice and glowing plants have used a Green Fluorescent Protein (GFP) from jellyfish, although several colours are now available for genetic markers.

Unlike some other sources of bioluminescence, GFP is coded by a single gene, and does not require other biological support structures.

The downside is that to produce the soft green glow, you must irradiate it by strong blue-violet light; perhaps not so different from the blue LEDS which some people are plastering all over their cars (because they can?).

I think for now, we should stick with visible light illumination and roadside retroreflectors, which is easier for humans to see than the diffuse glow of GFP-infused grasses or shrubbery.

If (or more likely, when) robotic cars become readily available, will infra-red vision be considered more effective at penetrating dust and fog? Imagine cars traveling in (apparent) total darkness...

[CliffordK]

I don't know if I'd plant a glowing tree.

If one could actually make a tree as bright as a million fireflies, then one may in fact get some usable light.  Producing light might be a pretty heavy drain on energy.  Perhaps one would have to choose only part of the tree such as glowing berries.  Pick something with fall/winter berries like a holly, and it would give new meaning to Christmas tree lights.  Especially if they would blink like the fireflies.

Apparently the fireflies produce light with respiration.  The trees, of course, produce oxygen, but they produce the oxygen during the day, but would need the light at night.

[alancalverd]

Street lights do light up a greater area than one's headlights.  The concern is not running into other cars (which have headlights on), but rather running into unexpected stuff like animals or people on the roads.

This would make logical sense if British motorways were lit in the rural sections (where you are more likely to encounter animals) or had any pedestrian access (they don't). In fact it's only the "urban" sections (which includes major intersections) that are lit, and these are exactly the places where fog scatter can cause accidents. Oncoming headlights are irrelevant as UK motorways are all one-way: what matters is the ability to see tail lights and passive reflectors, which are more obvious in the dark.

[alancalverd]

If one could actually make a tree as bright as a million fireflies, then one may in fact get some usable light.

What matters in roadway delineation is point brightness, not illumination. One firefly is perfectly visible, as is a single "cat's eye" reflector, but you couldn't use either to read a newspaper. I recently sailed down a river on a moonless night, with nothing but fireflies to show the position of the banks.

Flying at night is no problem. Aircraft navigation lights are remarkably low powered - maybe 5 watts on each wingtip  - but visible for several miles in a clear black sky, and runway lead-in and edge lights do not illuminate anything. Landing and taxi lights are just like car headlamps, and we take care to keep the runways and taxiways as dark as possible to preserve night vision right up to the apron. The same philosophy applies to night lighting at sea.  I'd like to see it applied to major roads.

[chris]

Replacing the crash barriers with wild roses would be a good idea. Unlike wire ropes or steel bars, they absorb energy and don't shunt the vehicle back into the traffic flow.

Alan - will this really work? What depth of roses would be needed to achieve the same carriageway-crossing-preventative-effect of the present barriers?

[CliffordK]

My grandmother hit a laurel hedge.  It totaled her car, and she ended up with a fractured cervical vertebrae.  Plants don't always give as soft as a landing as one hopes. 

Here in the USA, they are putting in cable guardrails into the median strips to prevent jumping across to opposing traffic.  One could use a cable barrier plus plants to slow down the cars.

In Egypt, they often drive at night with just clearance lights, especially when passing other vehicles, as you mentioned to help dark adapt their eyes. 

But, it is pretty wide open in the Egyptian countryside, and almost with clear nights.

[Himself]

The issue with using GFP is that it only functions in the presence of arabinose. I think a major challenge would be getting the grass to intake this molecule (If it does not do so already), not to mention what would happen in areas with insufficient amounts. Even with the grass on the road, I think the street lights should remain as a fallback.