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Re: Optimized DRL system?
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CarGuru > Driving > Re: Optimized DRL system? 2 May 2005 03:17:37

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Re: Optimized DRL system?

Daniel J. Stern 2 May 2005 03:17:37
 
It would be better if the systems were designed to optimize the DRL > > function and encourage proper, rather than improper, driver operation > > of vehicle lighting systems.
And what, in your opinion, would the ideal system consist of?

Definition and placement:

1) A system shall consist of one daylight running lamp mounted within 10cm
of both the left and right front corners of every motor vehicle.

Rationale: Accurate position and width indication, physical visibility at
wide lateral angles, compatibility with positional requirements for other
conspicuity devices (parking/position lamps, front turn signals)

2) Mounted no lower than 20cm below nor 20cm above headlamp centreline
height

Rationale: Accurate position indication, avoids DRLs placed too low (e.g.
in 'fog lamp' location) for distance visibility

Performance:

3) Axial (straight-ahead) intensity of 600 to 1500 candela at 13.5v

Rationale: distance conspicuity for 2-lane highway overtaking judgements,
compatibility with existing regulations and technology, adherence to
intensities found by research to provide significantly increased
conspicuity, avoidance of glare, avoidance of driver confusion with
headlamps, avoidance of motorcycle masking.

4) Lateral intensity distribution of 80% of maximum axial intensity at 5°
inboard and outboard, 70% at 10° inboard and outboard, 40% at 25° outboard
-- from 10° up to 5° down.

Rationale: Angular conspicuity for intersection and pedestrian/cyclist
collision avoidance (10° up requirement for compatibility with higher
driver eye heights in taller vehicles, 5° down requirement to avoid
casting an apparent beam on the road surface at night, thus avoiding
driver confusion with headlamps)

5) Colour of light emitted: Selective Yellow to Yellow-green

Rationale: Colour differentiation from headlamps for driver identification
of function/avoidance of confusion with headlamps, and for lighting-usage
identification by law enforcement officers. Adherence to research showing
potential conspicuity benefit of coloured DRL vs. white, without
introducing ambiguity into front turn signals. Compatibility with required
colour of parking/position light function to facilitate dual-function
lamps (Selective Yellow), compatibility with available LED emitter light
colour (yellow-green), human visual system is most sensitive to
yellow-green.

Size:

6) Minimum optically-active projected surface area of 24 square
centimetres

Rationale: Sufficient size of light source for visual aquisition and
tracking by observers, avoidance of glare through limitation of apparent
luminance, compatibility with surface area requirements of other
conspicuity devices (turn signals, etc.)

Electrical connection:

7) Must illuminate automatically when vehicle is in motion, independently
of any other lamp(s).

Rationale: Improved forward conspicuity without deleterious effects of
daytime tail/marker lamp usage (reduced brake lamp conspicuity, shorter
tail/marker life)

8) Must not illuminate when headlamps and/or front fog lamps are
illuminated.

Rationale: Avoidance of backdazzle (off w/front fog lamps), functional
separation (off w/headlamps)

9) Must illuminate when parking lamps are illuminated unless vehicle is in
a condition that prevents motion (parking brake applied and/or
transmission selector in "Park" or "Neutral")

Rationale: Prevents deliberate driver override of DRL by switching on
parking lamps, provides adequate daytime conspicuity in poor weather
without using headlamps (must illuminate with parking lamps), permits
nighttime differentiation of parked vs. moving vehicle (parking
brake/trans selector exemption)

10) Vehicle controls and displays shall not illuminate except when
headlamps and/or front fog lamps are illuminated.

Rationale: Encourage proper driver behaviour by leaving controls and
displays dark unless lamps legal and safe for nighttime driving are
activated. Solves problem of driver fiddling with headlamp switch at night
until instrument cluster is illuminated, resulting in nighttime driving
with parkers-only or parkers-plus-DRL.

11) Parking, marker, tail lamps shall illuminate when front windshield
wiper switch is in any "on" position.

Rationale: Provides 360° daytime conspicuity in conditions of reduced
visibility -- DRLs remain active per (9). Headlamps remain under driver
control.

Other factors:

12) Power consumption: Each daylight running lamp shall consume no more
than 16w at 12.0v

Rationale: Mitigation of extra fuel consumption and resultant emissions
from DRL-equipped vehicles. Compatibility with existing technology and
implementation. Ensure DRLs are compatible with Kyoto compliance in
applicable countries.

13) Durability: DRL light source shall have a Tc life rating of no shorter
than 700 hours at design voltage.

Rationale: Control burnout frequency to minimize DRL downtime and end-user
cost and inconvenience (Tc is the durability in hours at which 63.2 of
tested lamps have failed, and is an industry standard life test point).
700hr figure is compatible with many existing light sources.

14) Vehicle certification or type approval: Vehicles equipped with DRL
shall undergo national emissions and fuel-consumption certification or
type approval tests with the DRL system intact and functioning.

Rationale: Elimination of the "GM exemption" allowing DRL-equipped
vehicles to be tested with DRLs disconnected. Encourage manufacturers to
adopt efficient, low-power solutions.

There are probably points in the above that could be quibbled back and
forth, but I think it's pretty close to a thoroughly optimized DRL system.

DS
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CarGuru > Driving > Re: Optimized DRL system? 2 May 2005 03:17:37

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