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| Thread ID: 71342 | 2006-08-02 23:06:00 | Headlights | Lizard (2409) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 475694 | 2006-08-03 21:17:00 | Fitting bulbs with much higher wattage than the lamp manufacturer designed for will cause increased dazzle on two accounts, that is why LTSA say don't do it. As I said headlamp design is complex and a compromise between dipped and main beam. The main design effort goes into ensuring a well formed dip beam that results in least dazzle whilst adequately illuminating the road. Lucas used to have a standard test road just outside Birmingham where various figures and signs could be placed for illumination tests. We had a special Hillman rigged up as an all purpose test vehicle. If the wattage is increased, then the amount of unintended stray light that is there anyway and causes dazzle, will be increased. In addition, if we are talking about conventional filament bulbs, then a higher wattage bulb will have a bigger filament with thicker wire, thus the light source is more extended. A larger extended light source than designed for will spread light much more than the designed shape of the dip beam, and cause more dazzle to oncoming drivers. Consideration of manufacturing tolerances on the parabolic reflectors, lens shape and positioning, and the position and size of the bulb filaments all have to be taken into account on the resultant distribution of beam shapes that occur in practice with lamps of the same model. The manufacturers recommendations as to bulb type should be adhered to, as there is no guarantee that an alternative bulb type will have its light source at the correct, or designed for focal position. |
Terry Porritt (14) | ||
| 475695 | 2006-08-03 21:38:00 | ... it is now illegal to drive with your fog lights on in good ol' NZ during the day... Anyone know the reasoning behind this? Fog lamps are yellow, right? And they are not as bright as normal beam headlights. Is it still legal to drive with normal headlights? If not, police are turning a blind eye since I see quite a few cars with headlights on during the day. |
Strommer (42) | ||
| 475696 | 2006-08-03 21:51:00 | Anyone know the reasoning behind this? Fog lamps are yellow, right? And they are not as bright as normal beam headlights. Is it still legal to drive with normal headlights? If not, police are turning a blind eye since I see quite a few cars with headlights on during the day. You forget about those fracking brite rear fog lites that these clowns with European cars seem to delight in turning on. These are the one the cops should be targeting. |
paulw (1826) | ||
| 475697 | 2006-08-03 22:25:00 | Anyone know the reasoning behind this? Fog lamps are yellow, right? And they are not as bright as normal beam headlights. Is it still legal to drive with normal headlights? If not, police are turning a blind eye since I see quite a few cars with headlights on during the day. Fog lamp can be white or amber. Yes it is legal to have normal headlights on during daylight. California used to be a "all lights or none" state. This was to thwart driving with the parking lights lit...they are called "parking lights" for a reason and if the vehicle was moving, it wasn't parked! The law has been changed to allow this exception. If you think you need some lights on to be more visible, park lights are a waste of time and you should be on dips. This is the time when the cars without lights become more dangerous as they can be overlooked in a stream of cars with lights on. |
PaulD (232) | ||
| 475698 | 2006-08-03 23:36:00 | I cannot think of an "optical reason" why fog lights should not be used in daytime running lights. Most likely it's because they don't conform to the specified positions for standard head lights. However, they should be legal to use in daytime fog surely? Otherwise the law is an ass :) Lights which are not positioned properly can give a false perception of distance of the on coming vehicle. For example, twin lights on a motorbike at night could be a car much further away, similarly the closely spaced lights of Land Rover can give the same impression. Properly designed fog lights reduce back glare reflected from the fog as much as possible and for the same reason are mounted as low as possible so that the driver looks over the beam rather than through the beam. There is no point in using fog lights simultaneously with headlights, because of the back glare from headlights, even when dipped. It has been debated for yonks and yonks whether an yellow or amber beam is better in fog. Tests have shown there is no difference to visible distance seen between white or yellow, ie, yellow light does not penetrate fog more, but back glare is perceived to be less with yellow light than white light, by many drivers. |
Terry Porritt (14) | ||
| 475699 | 2006-08-04 00:14:00 | I cannot think of an "optical reason" why fog lights should not be used in daytime running lights. Most likely it's because they don't conform to the specified positions for standard head lights. However, they should be legal to use in daytime fog surely? Otherwise the law is an ass :) From an LTSA doc "Fog lamps are designed to emit a diffuse beam of light with a wide-beam pattern that has the potential to seriously dazzle other road users, particularly if they are not installed in a dipped position." |
PaulD (232) | ||
| 475700 | 2006-08-04 01:21:00 | From an LTSA doc "Fog lamps are designed to emit a diffuse beam of light with a wide-beam pattern that has the potential to seriously dazzle other road users, particularly if they are not installed in a dipped position." I have seen that and it is a nonsense. As I said, properly designed fog lamps are designed so as back glare in fog is minimised, so as to enable the driver to see the road a short distance ahead. By definition, if there is little or no reflected backglare, then there is no stray light shining up and sideways going into opposing drivers eyes. If fog lamps are not mounted in a "dipped position", ie the direction they are designed for, then they will not work properly as fog lamps, but produce back glare. So they are no different to any other lamp causing dazzle if not mounted and aimed properly. |
Terry Porritt (14) | ||
| 475701 | 2006-08-04 01:31:00 | Exactly , my fog lamps range is very short and dipped that I think my standard driving lights would cause more dazzle than my fog :rolleyes: | SKT174 (1319) | ||
| 475702 | 2006-08-04 02:04:00 | So they are no different to any other lamp causing dazzle if not mounted and aimed properly. Traditionally the fog lamps on a car were at bumper height to reduce back glare. The imports causing most problems were 4wds with the fogs between the headlamps, both mounted above a normal car driving position and the fogs seemingly permanently on. If a car should be on dip I can't see why it should have more than 2 significant lights on. |
PaulD (232) | ||
| 475703 | 2006-08-04 04:25:00 | Right Paul, that explains a lot. Vehicles with high mounted lights do tend to cause dazzle problems, even if their lights are correctly aimed. 4WDs with high lights should really have them aimed with the main beam pointed downwards slightly rather than parallel to the ground, which is what I do with my van lights. (Especially as 4WDs are driven mainly around urban areas anyway :) ) | Terry Porritt (14) | ||
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