DARMSTADT
`UNIVERSITY OF
`TECHNOLOGY
`
`PROGRESS IN AUTOMOBILE LIGHTING
`
`Department of Lighting Technology
`September 28/29, 1999
`
`FOUNTAIN AT MATHILDENHOHE, DARMSTADT
`
`
`
`
`
`
`
`
`
`
`
`Mercedes EX1024
`U.S. Patent No. 11,208,029
`
`

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`dedicated to
`
`Mr. Reinhard Ropke
`
`

`

`28 I 29 September, 1999
`
`Proceedings of the Conference
`
`Lichttechnik Darmstadt
`
`Published by
`
`Prof. Dr.-lng. H.-J. Schmidt-Clausen
`Darmstadt University of Technology
`
`Eigentum der
`AUDIAG
`D-85045 lngolst.R..-,1,
`
`UTZ
`Herbert Utz Verlag - Wissenschaft
`Mi..inchen 1999
`
`

`

`ISBN 3-89675-920-5
`
`PAL '99: 2 Volumes, Vol. 5 & Vol. 6; not to be sold separately
`
`Die Deutsche Bibliothek- CIP-Einheitsaufnahme
`Progress in automobile lighting/ Darmstadt, University of Technology,
`Department of Lighting Technology. Publ. by. H.-J. Schmidt-Clausen. -
`Munchen : Utz, Wiss.
`Vol. 6. PAL '99 : 28./29. September, 1999 ; proceedings of the conference/
`Lichttechnik Darmstadt. - 1999
`ISBN 3-89675-920-5
`
`Das Werk ist urheberrechtlk:h geschutzt. Die dadurch begrundeten Rechte, insbesondere die der Ober(cid:173)
`setzung, des Nachdrucks, der Entnahme von Abbildungen, der Funksendung, der Wiedergabe auf photo(cid:173)
`mechanischem oder ahnlichem Wege und der Speicherung in Datenverarbeiturigsanlagen bleiben, auch
`bei nur auszugsweiser Verwertung, vorbehalten.
`
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`berechtigt auch ohne besondere Kennzeichnung nicht zu der Annahme, daB solche Namen in Sinne der
`Warenzeichen- und Markenschutz-Gesetzgebung als frei zu betrachten waren und daher von jedermann
`benutzt werden durften.
`
`Copyright © 1999 Herbert Utz Verlag GmbH
`
`Druck: drucken + binden gmbh, Munchen
`
`Herbert Utz Verlag GmbH, Munchen
`Tel.: 089-277791-00
`Fax: 089-277791-0.1
`utz@utzverlag.com
`www.utzverlag.com
`
`

`

`Lighting Performance Requirements in Vehicle Lighting
`Exemplified by System Requirements for AFS -
`
`Hanno Westermann
`
`HELLA KG Hueck & Co., Lippstadt
`
`Lighting Performance Requirements in Interior and Public Lighting.
`When early this century first lighting requirements were normalised, preference
`was given to specify and classify the photometric characteristics of the
`luminaires and to give simple recipes about their arrangement. For public and
`interior lighting, this practice was left already in the 40th (in UK in the 60th) and
`replaced by illuminating requirements for the space to be illuminated. The way
`and with what means this had be done was left open, except that in directions
`where glare could be expected, the maximum luminous intensities of the
`luminaires were specified. In the 60th additional qualifying specifications were
`introduced to improve comfort and visual performance. They were based on
`luminance in the field of view - the only what is pictured in the human eye and
`to
`lead
`this
`lighting
`Interior
`In
`as such seen as visual environment.
`specifications on modelling or agreeable "room and object appearance" by the
`spatial ratios of incident light and it also lead to luminance requirements and
`classes of luminaires for normal directions of view but also infield vision of the
`luminaires themselves. In public lighting the road surface luminance and its
`uniformity (in dry condition) was introduced. Because of the mainly extra- foveal
`appearance of luminaires in the field of view of drivers, glare was specified in
`terms of eye illuminance and this again is transformed into limited intensities of
`luminaires for specified directions towards the traffic flow. These changes have
`not only improved the visual comfort in interior and exterior lighting, they have
`installations
`also considerably widened the freedom of design of lighting
`allowing great vc:triations in arrangements and technologies in interior as well as
`in public lighting, e.g. catinary lighting for public roads where fog prevails or
`floodlighting of complicated intersections or 6 and 8 lane roads. Subsequent
`
`;
`
`807
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`

`

`new technologies and designs could be applied without the necessity to change
`requirements. One can say, that these fields of lighting application have settl_ed
`in terms of performance requirements independently of and including further
`technological progress.
`
`Practice in Vehicle Lighting Requirements
`
`None of this changes entered into vehicle lighting requirements and still today
`the functional lighting devices are individually specified with respect to their
`spatial luminous intensity distribution and restrictive specifications on apparent
`shape and mounting on the vehicle. This seems partly to be justified by the fact,
`that all mandatory .vehicle lighting devices form together an information system,
`providing information on presenceand changes of movements of vehicles in the
`traffic flow. It seems however not justified where it concerns the front lighting
`performance. For front lighting not only different practice has developed in USA
`and Europe, but - in the absence of clear performance requirements - many if
`not most of technologic developments in light sources and lighting technology
`have caused and are still causing adaptive changes of regulations before such
`more economic or better performing technologies become applicable. This is
`equally the case for signalling devices. It is a rather sad experience of the
`regulators of being steadily kept on-work for amending old items while new
`issues have often to wait for treatment. This resulted in the expressed wish of
`WP29, that vehicle safety requirements be preferably formulated in terms of
`than specifying constructional or material
`functional performance rather
`characteristics of devices.
`
`In the 80th NHTSA tried to introduce front lighting performance in terms of
`spatial illuminances - but struggled on the proposed measuring concept. The
`in
`AFS project is again aiming at adaptable front lighting system performance
`order to create more possibilities of complex and integrated designs than the
`more conventional concept were NHTSA had strived for. AFS will obviously
`encounter more problems in finding an adequate and - from traffic point of view
`- a "safe" method for performance and approval testing of such systems before
`and after such AFS systems are installed on vehicles. Before tackling this
`challenging issue of the future, allow me some more remarks on the past.
`
`808
`
`

`

`From Branching National to Harmonised International Requirements.
`It is for sure, that national regulations have been for long a political issue of
`protecting national interests. But, the still existing differences in Regulations
`have also a sound basis in differing technology and traffic practice. Today, with
`international
`globalising markets, such differences are disturbing and
`"harmonisation" has become a key issue - but on which premises? Averaging
`regional standards which ·are both good practice in order to become one single
`requirement may sound simple - but it is definitely not a wise way as I will show
`you.
`
`Existing Headlighting Practice in Europe and USA
`Although different technol~gy With in Europe shielded bulbs and in the United
`States sealed beam headlamps, have . caused a difference in photometric
`properties - in Europe ~ith_. a defined ct,1t-6ff put low utilisation of lqminous flux,
`in the USA with high~r Valu~s above the horizon for longer reach on the own
`traffic lane and. with higher utilisation of luminous flux. It was prirnarily: the
`different traffic environment which had caused this different choice which in both
`c'ases is sound and most adequate.
`
`· "
`
`'<
`
`• •
`
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`
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`
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`
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`
`809
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`

`

`Fig. 1. 1 European Practice Based on 6 m Rural Road Compared to
`US Practice Based on Highways with Separated Lanes
`
`Between Europe and USA a principal difference exists (Fig.1.1 ). In Europe most
`of the traffic flow and of accidents is concentrated on country and urban roads,
`where mot fatalities occur - highways with separated lanes were most safe in
`terms of accidents and still are today. In USA most of the traffic flow was
`concentrated on Interstate and similar highways with separated traffic lanes,
`and this was also the case in urban areas. If we look on the main difference and
`struggles of harmonisation - glare· values - it becomes evident that from local
`practice point of view, no difference exists. Why? - Both, discomfort· and
`disability glare, depend strongly. on the peripheral angle under which glare·
`sources appear in the field of view. The central reserve of highways as
`in
`compared to rural dual carriageways enlarges this "glare angle" and
`consequence allows for the same discomfort a glare intensity at a given
`
`810
`
`

`

`distance twice the value (for disability glare more than ten times the intensity
`would be equivalent). On the other side, the higher speed on highways
`demands for a longer visibility reach than on small and curvy rural and urban
`roads, which have also speed limitation (see Fig.1.2). Both practices were
`evidently well defined and most adequate - but, an average of two practices
`would harm the visual performance in both cases, leaving less reach on
`highways and introducing great dazzle for opposers on small rural and urban
`roads. The solution in this conflict is either to combine the better parts of both -
`low gla're values and far reach - or to define highway lighting different from that
`of dual carriage roads. The one way of approach is covered by the progress in
`harmonisation, the other is incorporated in the AFS philosophy. It would be
`wrong, however, to see AFS as an alternative to harmonisation - AFS includes
`the possibilities which harmonisation offers but it goes a step further in offering
`alternative possibilities on top.
`
`I
`
`811
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`

`

`1 , 6
`
`::c ECE-Std.
`
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`Side Oist·ances
`Eye to Headlamp
`
`1,5
`
`2,5
`
`R u r a I a -n d U r b a n
`
`7, 70
`
`11, 50
`
`15,25
`
`1 3, 70
`Motorway/lnr:·erSta·te Highw._ay
`
`17, 50
`
`DISABILITY GLARE
`Schmidt-Clausen/Bindels 1971
`
`L\S = 0,013 + 0,037 X l..ct + 0,419 ( (;ye/ 02.°)
`
`,,.,........
`
`1, / 12 = ( 0/02 )2,0
`
`DISCOMFORT GLARE
`Schmidt.Clausen/Bindels 1971
`,r;---
`0,46
`W = 1,59 + 2 log (1 + y ... aci) - 2 log {EeyJ E> )
`
`s/m
`
`_ . _ . _ _ _ --+---+------+-----+---+---+---+---+---+--+--+----+--+----t--+--,l'--1-/--1--< 25
`I
`\
`f
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`--+-\---1-----1---1---+---+------l-l----+-l--+--+----f--+--'-+--+-----I---I 20
`\
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`F act:-o-+ .. ->-1~<::ro=-~-t---if---+--+-_ USAJ-figbway--+--+--+-,--~1±-a-+-:t::-t:4 -,r-t::t2=-_±.,=-15
`s > ,I~i7 m< ---1--/'--+----l--+---!-+--+------1
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`15
`
`10
`
`Fig. 1.2
`
`Luminous Intensity Ratio for Equivalent Glare on
`Motorways relative to the ECE Rural Standard Road
`812
`
`

`

`.
`
`.
`
`Overhead Sign Lighting
`This is also a field of divergence where something needs to be done to solve
`the problem without introducing unfeasible requirements in Regulations or
`detrimenting visibility for 99% of cases in order to satisfy the 1 % of occurrence
`of overhead signs which again are dominantly on highways only and scarcely
`on rural roads. What is the problem here?
`Overhead signs appear in the zone where low luminous intensities are specified
`in order to protect from excessive glare. Such low glare intensities are not
`directly calculable but result mainly - beyond strict screening and optical control
`of direct and reflected light being emitted - from biasing secondary and non(cid:173)
`controllable spread light such as reflexes from lead wires, coil and bulb reflexes
`. and from · inter-reflections of higher order on curved glass, prismatic edges or
`interreflecting parts of reflector and housing. If in order to illuminate overhead
`signs the spread light is not only to be avoided but has purposly to be designed
`to be repeatably and quantitatively present (CoP), this is contraproductive to the
`glare values and makes them rise (Fig.2).
`
`E C E · P h o t o m e t r I c
`
`·M e a s u r I n g S c r e e n
`
`POINTS FOR
`ZONE OF
`GLARE PROTECTION OVERHEAD SIGNS
`
`Overhead Sign Statistics Projected on the
`measuring screen: the upper 6 points are well choser
`(Thesis J. Damasky, 1995)
`Read in
`
`H
`
`Strong interference of point minima with zone maxima.
`To provide all point minima, the zone maxima will rise.
`Overhead sign lighting (temporary n-d) is detrimental
`to glare (all time).
`
`Either increase the intensity separate from headlarr
`e.g. from front position lamp
`or provide teporary special overhead sign light
`for a short period of time
`
`Fig. 2 The temporary usefulness of overhead sign lighting interferes
`with the need of continuous of glare protection by rising the
`glare values - this conflict needs a more adequate solution.
`
`Grouping the point values for overhead sign lighting as being proposed is one
`possibility to cope with statistics of biasing spread light. A special illuminating
`source for overhead sign lighting would be an other, more adequate solution. In
`the latter case account of, or even rising the luminous intensities of front
`
`813
`
`

`

`position lamps may be the solution, or introducing a special fixture which is
`designed for temporary use · as an overhead sign light. Any other way is no
`solution but a conflict relative to glare protection or overhead sign lighting
`introducing risks of non compliance or even lies which can not be the purpose
`of any regulation. In this case again, AFS offers such possibilities which perform
`but also the m~t recent proposal for harmonised dipped beam
`properly -
`lighting enhances such a possibility.
`
`The AFS Concept·
`
`into system performance
`that a move
`Both examples show clearly,
`to escape continuous
`requirements would be a wishful way not only
`amendments and corrections of regulations with any new technological
`· progress, but also to support a more general trend for improved active safety by
`creating and leaving a choice for higher front lighting qualities, which do not
`interfere with but just extend existing lighting practice to a higher level of
`performance for common adverse situations. The problem lies not in mjssing
`knowledge, what should and can be improved, but how a variable and as such
`functional
`lighting performances can be checked on proper
`adaptable
`performance and be approved in a similar way as is today's' practice.
`Already in the sixties first approaches towards a performance approach with
`multiple use of overlaid beams was made (Fig.3) - but abandoned because of
`the non- reproducibility of the necessary filament and positioning precision - at
`that time.
`
`814
`
`

`

`PHILIPS Res ea r c h R e vi e w
`First halogen development
`(before Hll with 3 transversal
`filament bulbs in 3 barabolic
`reflectors
`
`l 9 6 2
`
`(Potential DRL)
`
`Main Beam
`
`Fog and Town Beam
`
`Dipped Beam
`
`Fig. 3 Concept of integrated headlamp design dating from 1962:
`4 to 5 lighting functions are enabled by three lamp devices.
`The concept was abandoned because of inaccuracies.
`
`But today, and looking in other lighting fields as we did, we find examples how
`performance could be traced on measurables. Primarily, the vehicles' lighting -
`such as it results from all lighting devices working together and contributing to
`task
`'" must enable proper visual
`task or function
`lighting
`intended
`an
`performance for the driver, and, secondly, the appearance of the lighting units
`(in luminance and luminous intensity) and their configuration on the vehicle
`must be recognised as an approaching vehicle but not produce dazzle or
`inconvenience for other road users. Since both aspects can be traced back on
`the active components of the system. By neglecting the lesser importance of
`the measurement of photometric performance would be most easy,
`parallaxis,
`be it not that the system performance is variable with the surrounds and
`for these ambient
`triggered by sensor signals which are representative
`conditions: whether the road is wet or dry, whether the vehicle is driving straight
`forward or in a curve, on a rural road or on a highway. This implies two
`problems. One is the quality of the sensor signal, which can be simple (wiper of
`front windows "on", steering angle of front wheels or speed of the vehicle) or
`information on actual ·road curvature,
`(digital GPS
`rather sophisticated
`information on distance of preceding or following vehicles etc.). These sensor
`signals and their "automatic" impact on control of vehicle forward lighting has to
`
`815
`
`

`

`adapt the lighting performance to the traffic conditions and to prevent from
`deteriorating glare effects for other road users. As long as lighting performance
`contains and maintains a minimum lighting quality which is comparable to actual
`requirements, the first issue of road illuminating performance should form no
`problem. It could, however, become a problem if during (or as a result of)
`"
`performance changes the glare values rise above the valid standards. Both
`testing.
`these performance effects have to be checked during approval
`Moreover, and in view of the dynamic of lighting performance, a fail safe
`requirement is indispensable which allows a safe continuation within the traffic
`flow or leaving it, and which avoids excess glare towards opposers - all under
`provision that the driver is attended to the occurrence of a system error.
`Thus the active lighting performance can be traced on measurables and
`if the varying
`corresponding checks be performed in laboratory conditions
`lighting performances are varied the same way as vehicle sensors and switches
`will do this later on the veh.icle. Equally all interrelations between active system
`parts which are visible to other road users can be checked on their merits of
`.marking the vehicle as such by tracing it to the mutual dimensional and - where
`necessary - luminance aspects as being intended to be used on the vehicle.
`After the system has been approved on its performing aspects by simulating the
`vehicle controls, the final operation on the vehicle has to be verified, whether
`the signals behave as was simulated (as used in the simulating device) and
`whether the mounting positions as foreseen in the system description are
`adequate.
`In principle, the variable performance of systems can be traced on photometry
`and system controls - but, as always, the devil may the hidden in the details and
`here the AFS development is progressing and analysing such possible details
`which could cause unsafe conditions and how to overcome them. This is the
`actual state of how performance requirements can be established for such a ·
`complex matter as an AFS system. The possibility to cope with complex
`performance requirements brings us back to the starting question: which are the
`functions and varying performances where AFS is aiming at.
`
`816
`
`

`

`The Function Tree of AFS
`
`Basically there will be passing and driving lights between which the driver is
`switching and there will be front position lamps and day time running lights. The
`difference starts with the directive that the photometric result in performance
`and appearance counts and not the <+">means <-">how such a performance is
`thus leaving more freedom of design and technologic
`physically created -
`development. The next difference exists in automatically controlled (or timely
`switched) photometric characteristics which adapt the lighting performance to
`the visual needs in typical ambient and driving conditions
`
`driving at night, at day or approaching a tunnel,
`
`driving on a rural, urban or an express road,
`
`driving straight forward, in a bend or turning-offthe road,
`
`driving in clear weather, on wet roads, in fog, heavy rain or snowfall,
`
`approaching an overhead sign, which also today with few spread light of
`some 60 cd only can easily be seen on great distance - but not be read.
`
`All these special conditions ask for different lighting performance of the passing
`and even the driving lighting. In the context of AFS they are abbreviated AL for
`adverse weather lighting, BL for bending light, CL for country road lighting, TL
`town lighting and ML motorway lighting and accomplished by OVL overhead
`sign lighting.
`
`As the new proposal for a harmonised dipped beam or for a harmonised front
`fog lamp already shows, the appropriate lighting of road kerbs and road bends
`can be effected by a wide light spread - but this needs more luminous flux and
`e.g. does not reduce glare in right curves, which a lateral movement of the
`asymmetric part of the beams could do with less power consumption, and this
`also applies to additional bending light . Such alternative possibilities which all ·
`to
`in comparison
`the drivers or opposers visual performance
`improve
`conventional frontlighting are included in AFS. However, it is left to the vehicle
`manufacturer, which one to choose.
`
`A gallup report on driver demands in France, Germany, Italy and Sweden had
`shown that the major interest and need for visual improvements is seen in
`
`817
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`

`

`adverse weather conditions, directly followed by visual improvements when
`driving in bends. Overhead signlighting, e.g. was not judged worth to spend
`any extra money and also motorway lighting gained no high priority.
`· Thus, let us concentrate on the situation when roads are wet and when it is
`raining. A major difference."'compared to dry roads is the strong forward
`reflection on wet roads of the light from headlamps. This makes the appearance
`(luminance) of the road surface rather dark but also causes, that vertical
`obstacles are more outstanding in positive contrast. The one would compensate
`the other, be it not that the road reflexes of headlights from opposing vehicles
`are so disturbing and veiling the recognition of the course of the road and of
`obstacles on or near the road. The responsible indirect luminous intensity to the
`eye via the road reflexes turn out to be much higher than the direct light from
`the headlamps. To improve the own vision and reduce the overall glare effects
`the beam pattern needs to be different - with laterally and longitudinally a further
`reach for better orientation, and with slightly increased direct glare but much
`less intensity to the most reflecting foreground, in order to minimise overall
`glare.
`I will not go into too much details - this will be done by the speakers that follow
`and you will also have the opportunity - be it not to drive - but at least to see six
`test vehicles which have been used during tests and which all provide one or
`more AFS subfunctions in different ways. The systems being different in design
`were all were judged as a wishful step towards an improved traffic safety in
`conditions which are known to be prawn to stress and accidents. Not all test
`equipment and vehicles used can be shown, but what can be shown gives an
`idea for what AFS stands for.
`Early and Late Night Show of AFS cars at the Darmstadt Airfield
`Before dark the six test vehicles which were used during AFS driving tests and
`their AFS concept and properties will be shown and be explained by the
`sponsors by a poster and hardware demonstration. This will inform on the
`functioning and type description of the AFS subfunctions which are installed,
`including their photometric performance and their control. The organisation in
`grpups and time is so arranged as to give everybody a chance to be adequately
`
`818
`
`

`

`informed and to get hopefully all the answers on open questions which may
`exist concerning the system.
`When it. is dark, all the vehicles will pass revue in front of the tribune to show
`their lighting performance and improvement for seeing the road course and
`obstacles in comparison to conventional headlights.
`
`Pity enough, the two days' symposium leaves no space for gaining driving
`experience individually. The promised presence of the cars during the GRE
`meeting made it possible to bring them here too a week earlier. However, if you
`will arrange a test drive and do not participate in the GRE meeting during the
`week after the PAL Symposium, please contact the vehicle sponsors for an
`arrangement.
`
`Further Proceedings of the AFS Project
`
`The AFS Project started on third of June 1993 with - at that time - 12
`manufacturers, which were interested in such an improvement program of
`active traffic safety. The challenge of such a system approach and the
`towards performance and system
`necessary and not so easy change
`requirements was clearly seen - but also the prospects of possible safety
`improvement. Meanwhile two phases - the feasibility and development phase -
`are finished (see Fig. 4). A lot of experience and information has been gathered
`by tests and research and all this knowledge has now to be transformed in a
`draft document which can serve as an entry in the process of rule making.
`
`819
`
`

`

`Expen
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`
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`
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`MAY
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`jF u n c tt on Develop rn en t
`F e a s i b i I i t .y S t u d y
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`
`93
`
`94
`
`95
`
`96
`
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`System I>e.v:el.op.ment
`
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`
`-orattReg.
`
`Initiative
`
`Action P an
`
`BRITE EuRam 111
`Application BE-97-4137
`8,3 M ECU - 20 Partners
`incl. 7 Research Institutes
`
`Fig. 4 AFS PROJECT DEVELOPMENT- ACTIVITIES and COST
`
`In this last phase eighteen 117embers stay behind the project in a rather global
`composition such that it is evident, that AFS is aiming at world-wide recognition of
`the requirements.
`
`2 LIGHT SOURCE
`MANUFACTURERS
`OSRAM
`PHILIPS
`
`u
`-· -
`
`LEK-CHRYSLER
`
`-SAAB
`
`VOLVO-cars
`VW/AUDI
`
`FIG. 5 AFS MEMBER COMPANIES
`
`820
`
`