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SAE J1398-1996: Stop Lamps for Motor Vehicles over 2032 mm Wide
⚠️ Cancellation Notice: SAE J1398-1996 was canceled in August 1996. While this standard is no longer active, its technical requirements remain foundational for many current regulations. Always verify the latest applicable standards for new designs.
📘 Overview and Scope
SAE J1398-1996 specifies test procedures, performance requirements, and guidelines for stop lamps intended for motor vehicles with an overall width of 2032 mm or more. These stop lamps may also be used on narrower vehicles. The standard is part of a series of SAE lighting standards and cross-references documents such as SAE J2139, J567, J576, J578, J586, and J759. The lighting identification code for these lamps is S2 per SAE J759.
🔍 Key Test Requirements
The standard mandates a series of environmental and photometric tests, as summarized in the table below. Most tests follow the procedures defined in SAE J2139 unless otherwise noted.
| Test | Reference | Essential Requirement |
|---|---|---|
| Vibration | SAE J2139 | Device must withstand specified vibration without damage or degradation. |
| Moisture | SAE J2139 | No moisture ingress affecting performance. |
| Dust | SAE J2139 | Dust must not impair optical function. |
| Corrosion | SAE J2139 | Resistance to corrosion under specified conditions. |
| Photometry | Table 1 (this standard) | Luminous intensity must meet minimum values at specified test points. |
| Color | SAE J578 | Stop lamp color must conform to SAE J578 red specification. |
| Plastic Materials | SAE J576 | Optical parts (lenses, reflectors) must comply with SAE J576. |
Photometric measurement notes: Light source must be at least 3 meters from the photometer. The H-V axis of the device is taken parallel to the vehicle’s longitudinal axis when mounted in its design position. For multiple compartment lamps or multiple lamp arrangements, two methods are acceptable: (1) test all compartments together if the angle from each light source to the photometer center does not exceed 0.6° – the H-V axis then intersects the midpoint between the light sources; or (2) test each compartment separately and sum the outputs at corresponding test points.
🛠️ Engineering Design Insight
📐 H-V Axis Alignment: When the lamp is in its designed mounting position, the H-V axis must be parallel to the vehicle’s longitudinal axis. This alignment is critical for accurate photometric measurements. Even small misalignments can lead to failing intensity readings in the intended field of view.
For assemblies using multiple compartments or lamps, note the following design constraints: if the distance between adjacent light sources exceeds 560 mm for two compartments/lamps, or 410 mm for three, each compartment must independently meet the photometric requirements of Table 1. Additionally, when a stop lamp is combined with a tail or clearance lamp, the stop lamp intensity must be at least three times the tail/clearance lamp intensity at any test point (and five times at H-V, H-5L, H-5R, and 5U-V).
Plastic materials used in lenses and reflectors must comply with SAE J576 to ensure long-term durability and optical clarity.
❓ Frequently Asked Questions
1. Which vehicles are covered by SAE J1398?
The standard applies to stop lamps on motor vehicles with an overall width of 2032 mm or more. However, lamps meeting the standard may also be used on narrower vehicles.
2. What is the H-V axis and why does it matter?
The H-V axis is the reference axis for photometric measurement. In this standard, it must be parallel to the vehicle’s longitudinal axis when the lamp is mounted. Proper alignment ensures that measured light output corresponds to the intended direction of the stop signal.
3. How should multiple-lamp assemblies be tested?
Multiple compartments or lamps can be photometered together only if the angle from each light source to the photometer center is ≤0.6°. Otherwise, test each separately and add the results. Also, spacing limits apply (560 mm for two lamps, 410 mm for three – if exceeded, each unit must meet requirements independently).
4. Is SAE J1398 still valid today?
No, the standard was canceled in August 1996. Designers should refer to current SAE or regulatory standards (e.g., FMVSS 108, SAE J2139) for stop lamp requirements on wide vehicles. However, the technical principles in J1398 remain relevant for legacy systems or as a design reference.
