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PostPosted: Mon Nov 14, 2011 7:52 am 
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Catenary lighting parallel with and located in the centre of dual carriageways has a number of advantages and disadvantages over conventional lighting, and these can be summarised as follows. There are likely to be more advantages and disadvantages than listed.

Advantages:

* Very even distribution of light on the road surface
* Low glare
* Efficient use of light produced (no wasted backspill)
* Reduced visual intrusion of the scheme
* Lighting can span crossroads without a break
* Highly reduced numbers of service connections

Disadvantages:

* High upfront capital cost
* Requires tall and heavy duty columns
* Maintenance issues due to adverse weather and ageing
* Crash damaged columns cannot easily be fixed


At the end of the day, the relatively high cost and difficulty of maintenance killed off the idea of using catenary lighting. But is it time to think again?

Some catenary lighting that still exists on the A30 and A4 in West London consists of Phosco P415 twin-135W SOX lanterns, with five lanterns per span. These lanterns can also be fitted with 180W SOX lamps. Anybody who has picked up a 135/180W leak transformer will know how heavy these are, so imagine 10 per span, plus the weight of the lanterns themselves. No wonder the columns had to be so heavy duty. But times have changed, and the majority of councils and contractors fit new lanterns with electronic control gear, which is considerably lighter in weight. That would cause reduced stresses on column and lantern fixings, and columns wouldn't need to be so heavy duty. Furthermore, if a CosmoPolis catenary lantern were designed it could be a tiny lantern. Some of us have seen how tiny a WRTL 2Tone is, and they can handle 140W CosmoPolis lamps. Smaller size means reduced windage, and again, reduced structural issues.

Then there is the matter of cost of installation. Columns that aren't so heavy duty means the cost of installing catenary lighting would be reduced compared with in the old days. But the biggest cost when it comes to installing street lighting nowadays is the charge that the electricity company requests for every service connection. Five years ago this stood at £1000 per lighting column, and it has risen significantly since then. The catenary lighting on the A30 and A4 is fed by a supply from every other column, but when you look at the spacings between columns it is clear to see how much money could be saved when it came to service transfers. When it comes to the capital cost of installing street lighting, the fewer columns the better, and catenary lighting takes this to another level.

Just a rough calculation based on the A30 catenary lighting compared with an adjacent section of conventional columns. A length of five catenary lighting spans (six columns) equates to about nine conventional columns (or 18 if located in the verges). Five catenary spans would require service connections to three columns, so let's call that £3000. Nine conventional columns, that's £9000. Over the five catenary spans, with four 150W SON lanterns per span, that's 20x 150W, which is 3kW. Conventional lighting requires 18x 250W SON lanterns, which is 4.5kW. Oops, somebody's car has left the road. 44% less chance of hitting a catenary lighting column... except in the event of hitting such a column, it would be more problematic. Catenary lighting columns aren't crash friendly and are designed to stay upright, and how do you replace a catenary lighting column easily?

Food for thought.


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PostPosted: Mon Nov 14, 2011 12:48 pm 
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sotonsteve wrote:
Some catenary lighting that still exists on the A30 and A4 in West London consists of Phosco P415 twin-135W SOX lanterns, with five lanterns per span. These lanterns can also be fitted with 180W SOX lamps. Anybody who has picked up a 135/180W leak transformer will know how heavy these are, so imagine 10 per span, plus the weight of the lanterns themselves. No wonder the columns had to be so heavy duty. But times have changed, and the majority of councils and contractors fit new lanterns with electronic control gear, which is considerably lighter in weight. That would cause reduced stresses on column and lantern fixings, and columns wouldn't need to be so heavy duty. Furthermore, if a CosmoPolis catenary lantern were designed it could be a tiny lantern. Some of us have seen how tiny a WRTL 2Tone is, and they can handle 140W CosmoPolis lamps. Smaller size means reduced windage, and again, reduced structural issues.


I think you've made a really good point. The M25 used to use lighter-weight catenary lanterns along some parts; these were effectively 'bricks' instead of the traditional CU Phosco P415. I wonder how heavy the SON catenary lanterns were on the M5? Even so, like you say newly designed catenary lanterns comparable in size to the WRTL 2Tone are an excellent idea and would mean thinner columns. However, I feel LED would offer the most potential. These could be distributed in single, spaced out catenary lanterns or many small units with smaller spacings spread out along the whole catenary system. The former would probably be best because it would mean less lantern maintenance in the same sense that less columns equates to less maintenance.

I think you've made an excellent argument to put forward in favour for the reinstatement of catenary lighting!

---

Does anyone know of any recent catenary installations on the continent? Since countries such as The Netherlands are big users, I would have thought they were still installing catenary systems in the 2000s?


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PostPosted: Mon Nov 14, 2011 1:39 pm 
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I would say that it won't catch on as the highways agency are trying to get rid of all the central reservation columns due to having to close off the fast lane when maintenance is due. And to move them to the sides so it’s the hard shoulder to be closed thus not affecting traffic flow. If you could do catenary on the side of the motorways then yes it would be a good idea but as sotonsteve said the disadvantages really does put it back on the shelf.

What would be better though is to have special optics so when you mount two lanterns off one columns side by side the left lantern shines the light to the left and forward and the right shines right and forward thus saving the need to mount twice the amount of columns.The down side is bigger dark patches when a columns is in an accident.


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PostPosted: Mon Nov 14, 2011 1:52 pm 
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It wouldn't matter on motorways but on council owned A-Roads e.g. A63 in Leeds it could work. I've often thought how all the older top entry Beta 5s could be stripped down and rebuilt, so rather than having a 35 W SOX lamp in use it could have an LED 'tray' of lamps and as a back up a MH lamp. There for a lantern is getting reused but at the same time the lantern. if painted up right, would look modern.
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If I can get hold of 3x Top Entry Thorn Beta 5s, I'd happily have a go at creating a modern 21st century catenary lighting system.

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PostPosted: Mon Nov 14, 2011 2:03 pm 
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I don't think LEDs in a Beta 5 would work. A 150W Metal Halide would work but the bowl would be a problem.


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PostPosted: Wed Nov 16, 2011 12:29 am 
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sotonsteve wrote:
Catenary lighting columns aren't crash friendly and are designed to stay upright, and how do you replace a catenary lighting column easily?


Well as the HA are so fond of installing concrete barriers in the central reservation, perhaps in future schemes they could install the catenary columns first and then put the barriers around them? This would vastly reduce the chances of the columns being damaged.


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PostPosted: Wed Nov 16, 2011 1:30 am 
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Exactly. Shame they can't develop a powered access vehicle that parks on the hard shoulder and can span right across up to 5 motorway lanes above the height of a double-deck lorry freight container - that would get rid of the lane closure issue! :lol:
The use of a lantern similar to a 2Tone for catenary spans would be an interesting one to see - even if just on local authority roads with a central reservation (round this way it'd be the dual carriageway section of Jockey Lane from the A1036 to Asda, and the link road at Clifton Moor from the A1237 to the Tesco roundabout - and those central reservations are wide enough to park a van on for maintenance)

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PostPosted: Thu Nov 17, 2011 12:10 am 
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Maybe we should e-mail a few lighting departments putting forward to them some of the arguments for catenary lighting and some of the modern solutions to the problems that used to befall it like my concrete barrier idea and the fact that modern lightweight lanterns can be sourced. Might make them think in these cost-cutting times. Some councils may never have considered it!


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PostPosted: Thu Nov 17, 2011 12:32 am 
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Gramma 6 - I agree to that above.

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PostPosted: Sat Nov 19, 2011 10:08 pm 
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I would be one who would like to see a return catenary lighting but perhaps with either CFL or LED lamps suspended to throw some light down on the road with interchanges and junctions lit with metal halide to provide more light. What about using wooden poles to support; if they can support overhead power lines surely they could do the job.
Three good reasons for using wooden poles:
1. Look better than steel and age naturally with out rust and don't require painting. They also last for decades with proper treatment.
2. One of the cheapest columns available.
3. In wide sections of roads, brackets could be added to support SON or MBI sapphires.


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