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ilp archive : journals

public lighting no. 33 vol. 9
April-June 1944

Editorial p37
Shall It Be "Black-out" Again? p37
Are we to endure another season of black-out? It may be possible that there will be a partial improvement in street lighting in the coming days. But no official pronouncement has given a hint of a "let up". So "be prepared." Keep the gear and equipment in good order and ready.
Lighting: ARP

Public Attraction p37
When the "lights to go up again" it is conceivable that people will walk the steets for the sheer joy of "seeing the lights." It is little more than a century ago when people flocked to Pall Mall. Unfortunately Piccadilly and may thousands of streets like it are in semi-darkness or even complete darkness. A day is not distant when the streets are "magnificently lighted" and "made safe for law-abiding citizens" and people will walk in safety.
Lighting: ARP, Lighting: History

The "Onion" p37
Readers will be grateful to Dr. J. W. P. Walsh for this article dealing with Isocandle and the Isocandle Diagram.
Lighting: Theory

A.P.L.E. Conference p37
It is possible, acting upon official advice, that the conference will be postponed. The demands on transport, other than for military or the services, will be ill-timed.
APLE: Conference

E.L.M.A. Luncheon p37
Some interesting speeches were heard, held recently at The Savoy, and street lighting received special attention. The President said "nothing has been more irksome to us than the dark discomforts of the black-out. People's hearts and eyes are crying out for light. It is our job to get it organised now to see that they get it."
Lighting: ARP

Personal p38
New Lighting Engineer For Newcastle p38
Mr. J. Grainger has been appointed Lighting Superintendent of the city in succession to Mr. R. Davison who has retired.
Lighting: Personnel

Technical School Appointment p38
Mr. D. G. Sandeman, B.Sc., A.M.I.E.E., Superintendent of Public Lighting at Stepney, has accepted an appointment as Lecturer in Electrical Engineering at East Ham Technical School.
Lighting: Personnel

Retirement p38
Mr. T. A. G. Margary has retired from the position of Borough Electrical Engineer of Wolverhampton in July. Mr. F. J. Elliott will be taking the role
Lighting: Personnel

Obituary p38
Mr. J. P. Blackmore p38
Public Lighting Superintendent to the Bombay Gas Company and member of the A.P.L.E. since 1925, died on May 30th after a short illness.
Lighting: Personnel

Quotation p38
"What is the part the lamp manufacturers will have to play in the stupendous task of resconstruction? There are: 5,000,000 new homes to be lighted; 4,000,000 old premises to be brought up to date; 1,000,0000 retail premises and 50,000 miles of streets to be lighted." - Mr. Chas. F. Dickson
Lighting: Statistics

Technical Problems Of The Gas Industry p38
Summary of the 4th Report of the Chairmen's Technical Committee of the Institution Of Gas Engineers. In order to coordinate the work of many Institution Committees, a senior Committee consisting of the Chairmen of these Committees sits at intervals and issues this annual report to the Council. The Gas Research Board is represented on this Committee so there is close liason between the Board and the technical problems of the industry.
Gas In Buildings
A Committee is drawing up Codes Of Practice relating to the installation and utilisation of gas in public buildings, domestic and private households and public street lighting.

Gas Engineering Advisory Service
The Gas Engineering Advisory Boards, setup throughout the country, include members from all Gas Undertakings, and are concentrating on improving the efficiency of the use of coal.

Gas Street Lighting
The earliest use of gas was for street lighting. The Joint Lighting Committee of the Institution Of Gas Engineers and of the Society Of British Gas Industries has considered the question of gas street lighting in the immediate post war period. It has sent to every Gas Undertaking a note urging the immediate necessity for overhauling its street lighting fittings and is considering plan for modifying and improving street-lighting installations to bring them up to the standard of the Final Report.

The general picture is of an industry that has panels of acknowledged experts always available to watch new developments and to decide upon the best practice for existing conditions. The high technical standard of gas is due in large measure to this interchange of ideas and mutual assistance.

The Importance Of Planning Lamp Positions In Street Lighting by H. W. Gregory, M.I.E.E p39
This paper was to be given at the Public Works Congress in November 1939. This was cancelled due to the war. Mr. Gregory, who was Vice-President of the A.P.L.E. died in 1940.

How had the principle direction of the practice of street lighting changed since the M.O.T. Report of August 1937 changed? It was the departure of lamp positions from a stereotyped pattern i.e. the "unit of system" in B.S.I. Specification No. 307 to the 'irregular planning' of lamp positions which arises from the necessity to study individually every lamp position to make it most effective in rendering good visibility. This arises from the principle that visibility is most efficiently obtained by means of silhouette where the object is viewed as a dark patch against a higher background brightness. This has been gaining ground for some years, was voiced in the M.O.T. Report and still remains unchallenged.
The opposite school of thought is represented on the Continent where cut-off and semi-cut-off lanterns at compartively close spacing are used to give high illumination on objects. Nothing was deduced that could cause any change of opinion in the minds of those who concluded that the silhouette method gives greatest visibility at a given cost.
The author is maintains that he continues to observe installations where better results could've been obtained by a complete rearrangement of lamp positions. Therefore this paper will stress the great importance of considering each lamp individually and guide the designer in weighing the relative importance of the factors involved.
So what were the reasons for the change of practice from high brightness of the object to high background brightness? Why the evolution of street lighting practice was so slow recognising this detail? This was largely due to the appearance of the electric discharge lamp which, at first, only provided high powered sources of light at relatively high capital cost. The higher output seemed to demand higher mounting heights and suggested the possibility of greater spacing to achieve economy. (Why didn't the arc lamp, processing similar features to the discharge lamp, brought about the advantages of working on background brightness? It did not because: (1) The redirection of light was difficult and (2) the labour problems retrimming the lamps overshadowed all other problems). This was my personal view when collaborating with the GEC on the first installation of the new lamps in Watford Road in 1933 - on the basis of the wider spacing it was practicable to push up the mounting height without unduly increasing the total first cost of the installation. The Watford lantern was particularly designed to avoid glare and give a good road brightness and that installation remains practically unaltered to this day.
Many workers have worked on background brightness: Mr. Lucas and his film showing the driver's view as he proceeds along the road The Importance of Kinematical Factors in Roadway Lighting 1935; Mr. C. Dunbar M.Sc. on Necessary Values of Brightness Contrast in Artificially Lighted Streets (I.E.S. 1938); Mr. F. C. Smith M.Inst.Gas.E. F.C.S on Reflection Factors and Revealing Power (I.E.S. 1938); and Mr. J. M. Waldram, B.Sc., A.C.G.I., F.Inst.P Road Surface Reflection Characteristics and their Influence on Street Lighting Practice (1934)
One frequently encounters fallacies showing that the mechanism for obtaining background brightness is misunderstood e.g. it is often believed that the shape of the T patch is under the control of the lantern's light distribution but this is not the case. I recollect my mistake assuming any long horizontal light source would broaden the patch of illumination where it only broadens it by the length of the source. The arrangement of glassware in the fitting can control the brilliancy of the light patch but cannot control its shape (except to shorten it in cut-off fittings). On the other hand it can control entirely the brightness of a body by direct illumination which is the principle used by older lanterns. The mounting height had an appreciable effect of the width of the light patch and will reduce glare. The author was attempting to produce two films showing (1) the light patch on the road surface varying with the lifting of the source and (2) the light patch varying with the turning of a directional light source horizontally through 360°.
Other early experiments with the Watford lantern utilising a stronger beam of light thrown in the direction of moving traffic proved disappointing as this defeated the principle of background brightness as the most effective form of visibiltiy. The directional lighting system of dual carriageways, perfected by the GEC, and which has been foudn to be most economical and effective, provides a direct contradiction to the early experiments of copying the beam of a motor car headlight to secure visibility. The economy effected on the Great Chertsey Road is that better visibility is obtained from 125W MB lamps than 400W MB lamps using the older arrangemnet: this provides some kind of rough measure of the comparative efficiency of obtaining visiblity by the two methods of object brightness and background brightness. It should also be noted that when obtaining visibility by object brightness there were always long stretches of mid-span position where the other conception of background brightness had to be relied upon. Consequently a driver was continually required to change his method of vision from one principle to another - by only using background brightness much fatigue and strain is obviated. For this reason alone it's worth the wholesale adoption of the newer principle and the scrapping of the old.
I belive the composition and colour of the road surface is far less important than one might at first suppose. At the high angles of reflection utilised, it is the degree of polish of the surface which matters, in securing the spread reflection of the light source, which secures the background brightness for us, and all types of road surface wear down to a common polish. The coarser grain of the surface associated with a non-slipping tendency provides better diffusion which broadens the light patch by the direct reflection of oblique rays falling on polished excrescences.
Vertical surfaces (such as hoardings) should be utilised to provide a bright background where available. The white painting of railings etc. should be exploited a good deal more, and perhaps compulsory powers to permit private railings on properties to be painted white should be permitted.
If we meet the requirements of the motorist then we meet the requirements of other road users.
The purpose of this paper is neither to indicate the methods of planning street lighting which have been generally adopted in the past, not to go into the details of standard methods of illuminating bends, road junctions, intersections and roundabouts. The principles involved in the siting of lamps for these special positions are: (1) To draw the attention of drivers at a distance to the presence of the turning, roundabout etc. (2) To reveal the presence of traffic in the turning or roundabout and its approaches and to make clear the confines of the carriageway.
A very common plan when designing installations during the past 30 years or more, has been to start with trial positions of lamps under review opposite the ends of road junctions, with the dual purpose of lighting the thoroughfare and providing a "mid-horizon" lamp for the use of traffic in the side-road approach. The requirements of the new specification are still in line with making this trial plan and fitting the remaining lamps in accordance with the principles set out in the specification. (A "mid-horizon" lamp is a useful principle. The light patch from this source is visible and effective to the greatest possible number of observers in the road. The recent technique for the lighting of bends may be said to utilize the same principle in repeating the "mid-horizon" lamp round the bend as the mid-horizon constantly changes as one proceeds. The insertion of additional lamp at intervals centrally suspended on roads exceeding 40' in width represents another use of this example).
When lighting a hill, the first few lamps are mounted "higher" - this broadens the light patches and improved brightness area will result at the foot of the hill. This light patch is also lengthened by the relative concavity of the road. Therefore the spacing here could be extended to around 180' if required. The up gradient will have greater areas of darkness between the patches of light on the hill because it is spread out vertically in perspective and we are looking at a much greater area of road.
One the observer starts climbing the gradient the appearance of the light patches are the same as if you were on the level. When you approach the crest of the hill there is extra glare from the lamps on the far gradient at eye level. This could be be avoided by guarding lamps on each side of the hillcrest or fitting louvres which would make them cut-off fittings - so then you'd need to close up the spacing on each side of the crest and use cut-off fittings. The relative convexity of the crest will also reduce the areas of the light patches and this, again, argues for closer spacing at this point.
The new specification greatly simplifies the planning of street lighting by resolving the eight former classes into Groups A and B. The MOT Report also specifies the power, mounting height and spacing and all one has to determine is the precise positions of individual lamps.
1. Primary objective in planning lamp positions should be to ensure as great a field of road brightness as possible, so approaching observer sees objects in silhouette.
2. Typical observer should represent a car driver whose requirements are most stringent. Meeting his requirements will generally satisfy those of other users.
3. Sufficneit light sources must be employed to ensure covering the road with light patches and ensure they coalesce.
4. In consequence a regular spacing of light sources (except on perfectly straight and level road) will be the exception rather than the rule. The slightest deviation must be treated as a bend.
5. A simple plan of the installation which gives no idea of the perspective view is insufficient on which to judge the merits of the design.
6. It is necessary to view the road itself with its boundaries and confines and changing elevations when finally planning any installation.
7. Vallleys in the road may not require special treatment but hill-crests may require closer spacing with cut-off fittings.
Lighting: Distribution, Lighting: Specifications, Lighting: Theory

Leading To Neatness And Order p42
Description of Siemen's Combined Service Unit in which is incorporated the sealing chamber, service fuse and link, meter, and consumer's main switch and fuses. It is designed to be "built-in" by the builders, so the three doors are flush with the door.

Road Accidents After Dark p42
During the past year, figures of road accidents were studied and analysed with a view to encouragement of all parties concerned to help reduce the number. The usefulness of the modified lighting on dark nights has been affirmed by police and citizens where it has been adopted. Whiteness of obstructions has continued; but few of our self-conscious British citizens have objeyed the request to wear white on their apparel at night. In some areas many, or many additional, illuminated signs were erected, directing to public shelters, first-aid posts, and other points of urgent resort in an air raid.
Lighting: ARP

E.L.M.A. Luncheon - Extracts From Some Of The Speeches p43
Summaries of speeches by The Rt. Hon. Lord Woolton, P.C., C.H and Dr. C. C. Paterson, O.B.E., F.R.S. Both speak of the challenges from the war faced by the lamp industry and for future plans (including standardisation and the fluorescent tube).
Lighting: Future, Lighting: Lamps

Priory Road, Birmingham p45
Pre-war night picture of the installation where the background was dark, so was brightened by painting the wall around the curve.
Lighting: Installations

Salford, A Pioneer p45
The City of Salford has recently celebrated its centenary of incorporation as a municipal borough. The Municipal Review states: "Salford is, not unjustly perhaps, proud of the fact that it was the first town in England to use gas for the purpose of street illumination, Chapel Street being lit by a local manufacturer two years before gas was introduced for street lighting in London."
Lighting: History, Lighting: Installations

Traffic Signals p45
Few authorities have removed the night-time cross to allow drivers to see traffic signals at night. This is a particular problem in summer. Mr. Stewart suggests "we may - perhaps when we are necessarily 'standing by' and not actually 'working' or fighting - give a thought to these problems."
Lighting: ARP

Electricity Service After The War p46
Mr. E. E. Hoadley, M.I.E.E., Borough Electrical Engineer of Maidstone, addressed the Town and County Planning Association at a lunch-time meeting where he put forward some constructive suggestions for improvements in living conditions for the post-war period. Speaking on the urgent need for more standardisation in electricity supply he said "There is not much wrong with the electricity supply industry. It is ludicrous to suggest nationalisation unless gas and coal are also nationalised. In any case the industry knows where improvements are needed. At its own expense 27 million pounds has been spent in standardising frequencies to 50 cycles per second, so there is no reason why the necessary further 17½ million should not be spend in standardising voltage to 230. The problem of apparatus manufacturing would then be solved. Such as standardisation would do away with the anomaly of a household moving and having to scrap all their fittings."

As It Should Be! p45
Pre-war night picture of the installation at St. Helier Avenue, Morden.
Lighting: Installations

Iso-candles Simplified, Or Onions Without Tears by John W. T. Walsh, M.A., D.Sc. p46
In the years before the war, there was increased use of the iso-candle diagram. It made its first really insistent demand for consideration where it appeared in the 1931 edition of the B.S. Specifciation for Street Lighting. Considerable use was made of it in two of the papers for the 1932 Conference.

The First Step
The shape, caused it to be named "the onion diagram", comes from the fact that no amount of ingenunity would enable the rind of an orage to be flattened out into a plate. The iso-candle diagram starts life as the surface of a sphere. Imagine a source of light to be placed in the centre of a large sphere of clear glass - "large" indicates that the sphere is so large compared with the dimensions of the source that it may be treated as a "point-source".
Lines of latitude and longitude can be plotted on the sphere, candle-power measured at each point, and lines drawn around the regions. These curves form elongated loops.

Flattening the Sphere
It might be thought that the spherical surface diagram would suffice. But this is not the case. Portions of the sphere near the edges of the diagram are squashed by comparison with those near the centre. A surface, originally spherical, cannot be satisfactorily flattened out, however it's sub-divided: distortion there must be, either of shape or area or both. But the map-maker has invented a scheme by which the distortion is of shape alone, and is called the Sinusoidal Equal-area Projection, sometimes called Sanson's Projection or Flamsteed's Projection.
Imagine unpeeling an orange with the peel complete for each of the natural sections. If these portions of peel are placed side by side they can be flattened out without much distortion of shape or area. Their edges refuse to fit together and it's at this stage that the distortion of shape occurs. If the pieces can be shifted horizontally until they touch then there's a distortion of the shape of each piece, but not of area.

The Angle Network
The iso-candle diagram must have a network of lines to indicate angles of latitude and longitude. The lines of latitude are spaced equally on the sphere. The lines of latitude on the sinusoidal diagram are likewise spaced at equal intervals from nadir to zenith. The lines of longitude have been affected by movement only and there was no change in length. Each line of latitude can be calculated by using a cosine table. The lines of longitude can be found by dividing the lines of latitude into equal parts.

Practical Applications
It can be used to find the candle-power of the source in any given direction. It can be used to find the polar curve of any given azimuthal (vertical) plane: chose convenient points on the line of longtitude and tabulate (a) angles from the nadir and (b) their candlepowers.
It can be used to calculate the total luminous flux emitted within any solid angle. First candle-power may be (and has been) defined as solid angular flux density. Think of a source of light placed in the centre of a sphere and imagine the candlepower is one candle in all directions: if the radius is one foot, then can cut out an area of one square foot i.e. one lumen; if the radius is two feet, then can cut out an area of four square feet i.e. one lumen. If the candle power is I candles then the flux escaping through the hole is I lumens. On an iso-candle diagram, the flux which would escape through any hole in the sphere can immediately be found i.e. divide the area of the hole by the square of the radius of the sphere and multiply by the average value of the candle-power for that area. Most iso-candle diagrams are hemispheres so the area of region is (2*pi squared).
It is often necessary to find the flux emitted within a given area of the diagram by boundary lines which are neither iso-candle lines or lines of latitude or longitude. The same general principle applies but it is difficult making a close estimate of the average value of the candle power over the whole area: therefore divide the whole area into any convenient number of smaller areas, each of a manageable size. Find the flux of each area and use simple addition to find the total.

Kerb Lines
On the onion diagram, the kerb lines are slightly altered, and not straight. They are specified using kerb distance ratios i.e. Kerb distance / Mounting height. The only luminous flux which reaches the roadway is that within the two road lines.

Finding Average Illumination
It is often desired to calculate the average illumination on the roadway. This calculation is fairly simple given (i) the iso-candle diagram and (2) the dimensions of the roadway, the mounting height and the position of each lamp in plan. First calculate the position of the kerb lines using kerb line ratios. Then find the flux emitted in this area: multiply by two as the neighbouring lamp is also considered. If the amount of flux is F then the amount reaching the roadway per square foot is, on average, 2F/(lamp spacing * road width). Since an illumination of one foot-candle is the result of one lumen of flux evenly distributed over a surface one square foot in area, then the average illumination of the roadway will be 2F/(lamp spacing * road width).

Calculating The Illumination At A Point
A simple problem is finding the illumination at any given point in the roadway. From a scale plan, mark the position of the lamp and the point in question. LP is intersected with the kerb and the angle of intersection is the angle of longitude. A line is drawn through the lamp point, perpendicular to LP of a length representing the height of the lamp. The angle LAP is measured and this is the angle of latitude. The value of candle-power at this point can then be read from the iso-candle diagram. The illumination at P is therefore the candle-power divided by the square of the distance and multiplied by the cosine of the angle of incidence. (Additional illumination from adjacent lamps can be found in a similar way).
Lighting: Theory

A Good Example Of Sieray Fluorescent Lighting p52
Picture of the interior of a large rolling mill. 250 tubes in reflector fittings.
Lighting: Installations

Central Suspension - Suitable For Narrow Streets p52
Picture of Hall Street, Dudley. Central suspension is used in this narrow street, so advantage taken from reflection from builidings, giving good road and background brightness.
Lighting: Installations

Gas Can Compete For Street Lighting - Some Frank Admissions by Mr. John W. Pallister, A.M.Inst.C.E., M.Inst.Gas.E. p53
Pallister surveyed the whole field of municipal gas undertaking at Middlesbrough.

Dometic Lighting
This should be abandoned, and done openly and not passively. It is time the industry took a realistic view of this matter. The impression is that gas is old fashioned and the revenue obtained from domestic gas lighting is outweighed by the damage it does to our prestige. Let the consumer see that we are modern and advocate. If the consumer requires the best means of cooking, space heating, water heating etc. then added weight is given to our recommendations. We still have domestic lighting in houses in the older parts of the town, where electric cables have not been laid or where the expense of wiring is considered too great.

Street Lighting
It may appear inconsistent to advocate gas for street lighting and decry it for domestic lighting but the advantages attached to the latter do not apply to the former. Street lamps are thoroughly cleaned, adjusted and remantled where necessary, once every ten days, and they are inspected every day. Reliable automatic control is easily applied and constantly burning by-passes are not necessary; and objections due to discolouration of ceilings and noise and heat of burners do not apply.
As Public Lighting Engineer to my Corporation with control of 3400 gas lamps to 53 electric lamps, gas can compete with electricity both economically and on technical grounds. Improvements will take place with both. There is a need for a gas lamp of higher lumen of lighting.
No attention has been given by the Government to public lighting in the post-war reorganisation of industries and public services. There may be the creation of a central lighting authority and it may be desirable to effect control by legislation. This would involve grants from the Exchequer to local authorities or the removal of the cost entirely from local rating to national funds.
I have drawn up plans for improved lighting with complete new installations for eight miles of main roads for submission to my Council after the war.
Lighting: Comparisons, Lighting: Funding, Lighting: Installations

From A Scottish Paper! p53
"100 Years Ago. On the 14th of last month all the street lamps in Montpellier were lighted with brandy, not Cognac, but trois six - such a quality, however, of that liquor that the lamps burnt for seven hours, emitting a bright, beautiful light, without smoke, and with a pleasant odour, to the last drop"
Lighting: History, Lighting: Installations

Letter p53
Happy New Year greating from the Lighting Engineer of Palestine.
Lighting: Personnel

War-Damage Extension Of Patents by S. T. Madeley p54
Many interesting points have been dealt with by the Courts since the Patents Acts of the 1942 Act came into force. These allow extensions of patent term not exceeding ten years to be granted where the patentee has suffered loss or damage due to the war.
Loss or damage due to the war must be proved. The maximum extension granted will be a period equal to that between the beginning of the war and the expiry of the patent.
A detailed example was given of a reflecting sign patent. Other interesting patent cases were summarised.
Lighting: ARP, Lighting: Legal

Adverts: Poles Ltd, The Association Of Metal Sprayers, Stanton Ironworks Co., Ltd Siemens Electric Lamps And Supplies Ltd., Metropolitan Vickers Electrical Co. Ltd, Engineering And Lighting Equipment Co. Ltd., Automatic Telephone And Electrical Co., Ltd., British Commercial Gas Association, W Parkinson And Co., Philips Lamps Ltd., The British Thomson-Houston Co. Ltd., Holophane Ltd., William Sugg And Co., Ltd., The Lighting Service Bureau, Walter Slingsby and Co., Ltd., The Horstmann Gear Co., Ltd., British, Foreign And Colonial Automatic Light Controlling Co., Ltd., Foster And Pullen Ltd., Sangamo Weston Ltd. and The General Electric Co., Ltd.