Interpretation ID: nht87-1.29

TYPE: INTERPRETATION-NHTSA

DATE: 02/06/87

FROM: HANNS-OTFRIED WESTERMANN--HELLA KG HUECK & CO.

TO: DR. BURGETT--NHTSA

TITLE: RE MULTI BULB DEVICES

ATTACHMT: ATTACHED TO LETTER DATED 8-22-90 TO H. WESTERMANN FROM P. J. RICE; (A36; STD. 108)

TEXT:

We intend to equip motor vehicles with signalling devices, which have - opposite to conventional lamps - a great number of replaceable miniature bulbs instead of e.g. one 32 cp bulb. The miniature bulbs are about 2 to 3 cp each, as is actually applied t o CHMSL.

This design shows a number of advantages:

1. The failure probability of the signal function of a device is very low, because the burn out of a single bulb does not drop the light-out-put of the lamp below the minimum value required.

2. The average life of the miniature-bulbs is greater than the one of current 32 cp bulbs: about 3 per cent mortality rate after 1500 burning hours.

3. The devices can be built smaller and particularly with less depth.

4. The openings in the vehicle's body work can be avoided in part or totally, because the devices can be surface mounted.

5. The absence of body work openings increases the vehicle's stability and avoids sealing problems.

Summary: "Multi-bulb-devices" increase the traffic safety and lower the system costs over the vehicle's life time.

FMVSS No. 108 opposes this idea, because it is required that lamps with 2, 3 or more lighted sections have to comply with higher intensity requirements than a lamp with only one compartment or bulb. The reason for this requirement is to assure a uniform ly conspicuous surface luminance. These higher intensity requirements because of the larger overall lens area are not applicable to our design with a great number of miniature bulbs.

In spite of the great number of bulbs (10 to 20, depending on function) the total area of the lamp is not larger than the one of current one-compartment-lamps. The luminous Intensity requirement for 3- or more compartment lamps for this lamp size would c ause undesirable high luminances.

For each of the many bulbs the lighted lens area is substantially smaller than the required minimum area (22 inches square) for each compartment of multi-compartment lamps, but the total area of all bulbs is in compliance with the requirement for one-com partment-lamps.

We kindly ask for your comment on the legal aspects of this deviating design with many miniature bulbs and in particular, whether the intensity requirements of single-compartment lamps are applicable. (For LED-lamps it is even discussed, that for their higher conspicuity the intensity requirements could be lowered below those of single-compartment lamps). In our opinion the minimum requirements should not depend on the type of design (number of bulbs or compartments) but on the overall visible lens ar ea.

We want to draw your attention to the changes of ECE Regulations R6 and R7:

"If with a single lamp containing more than one bulb one of this bulbs fails, the lamp with the remaining bulbs shall comply with the minimum value required ...

Any failure of a bulb in such a lamp shall be clearly visible, if the lamp is switched on."