Interpretation ID: 571.141 NCC-230601-001 Nagaraj-Superhorn

September 13, 2023

Mr. Suraj Nagaraj
Director, Vehicle Homologation
Tesla Motors, Inc.
3500 Deer Creek Road Palo Alto, CA 94304
snagaraj@tesla.com

Dear Mr. Nagaraj,

This letter responds to your inquiry to the National Highway Traffic Safety Administration (NHTSA) regarding compliance of a new horn function named “Superhorn” with Federal Motor Vehicle Safety Standard (FMVSS) No. 141. Based on the information you provided, as explained in more detail below, we have concluded that Superhorn is permissible under FMVSS No. 141.

Description of the Superhorn

You state that Superhorn is a feature that plays a horn sound through the same system used for emitting the pedestrian alert sound; the vehicle would not be equipped with a traditional horn trumpet. In addition to being user-actuated, you state that Superhorn would resemble a traditional horn both in sound and loudness and would only be played for the duration of continuous horn control actuation (up to a maximum of a 60 seconds before the system times out). You further state that Superhorn is independent of the pedestrian alert system, and that the pedestrian alert system would be emitted alongside the Superhorn sound from the same speaker system. You acknowledge that the pedestrian alert sound may be masked to some extent by the horn when the horn is actuated.

Background

NHTSA established FMVSS No. 141 in 2016, pursuant to the Pedestrian Safety Enhancement Act of 2010 (PSEA).1 The standard sets minimum sound level requirements for hybrid and electric light vehicles operating at low speeds and aims to reduce injuries to pedestrians and other road users by increasing the detectability of hybrid and electric vehicles.

NHTSA does not approve motor vehicles or motor vehicle equipment and does not determine whether a product conforms to the FMVSS outside of an agency compliance proceeding.
Instead, the Safety Act requires manufacturers to self-certify that their products conform to all applicable FMVSS that are in effect on the date of manufacture. NHTSA also investigates safety-related defects.

Discussion

There are three requirements of FMVSS No. 141 pertinent to the analysis of the Superhorn.

Sound performance requirements (S5.1 through S5.4)

S5.1 through S5.4 describe performance characteristics related to measured volume and frequency bands of sounds emitted from covered vehicles. The volume and frequency requirements described in S5.1 through S5.4 are vehicle-level requirements; individual sounds such as horns, including the proposed Superhorn, are not required to independently meet those requirements.2

The performance requirements described in S5.1 through S5.4 are intended to measure the detectability of a vehicle during routine operation. Since the Superhorn is not automatically engaged during routine operation, the Superhorn may not be used to meet FMVSS No. 141’s minimum required sound levels.3

Sameness requirement (S5.5)

S5.5 describes the “Sameness requirement,” which requires all vehicles of the same make, model and trim equipped with a pedestrian alert sound to emit the same set of sounds. NHTSA has previously explained that the Sameness requirement, which stems from the PSEA,4 only applies to sounds added to the vehicle for the purposes of complying with the standard.5 The agency believes that this interpretation is still appropriate. Requiring all sounds produced by non- pedestrian alert systems to be identical would be overly burdensome and would prevent certain optional equipment that could affect the sound of a vehicle from being offered for sale.

Even though the Superhorn would be played through the same speaker system as the pedestrian alert system, according to your description it is not being added to meet volume and frequency requirements of FMVSS No. 141, and it is only active during horn control actuation. Therefore, Superhorn is not subject to the Sameness requirement.

Prohibition on altering the sound of a covered vehicle (S8(b))

S8(b) prohibits providing “any mechanism, equipment, process, or device intended to disable, alter, replace, or modify the sound emitting capability of a vehicle subject to this standard, except in connection with a repair of vehicle malfunction or to remedy a defect or non-compliance.” S8(b) is derived from a similar provision in the PSEA.6 In proposing S8(b), NHTSA described the intention of the provision as “to avoid the situation where vehicle sounds are changed, at the request of the consumer, to something individualized and no longer associated with the specific make/model of motor vehicle, or indeed even recognizable as a motor vehicle at all.”7 NHTSA reaffirmed this position in response to a petition for reconsideration, stating that S8 is intended to prevent access to vehicle features that could modify or adjust the emitted sound or render it noncompliant.8

As a practical matter, NHTSA has not applied S8(b) to other vehicle devices or mechanisms such as traditional horns or audio systems, even though these systems have the potential to alter the sound produced by vehicles and how they are perceived by pedestrians. NHTSA views S8(b) as preserving the integrity of the pedestrian alert system and, more generally, the vehicle’s detectability by pedestrians. Devices that directly touch upon the vehicle alert system, including a vehicle’s pedestrian alert speakers or audio file, receive a higher level of scrutiny. This is not to imply, however, that these are the only systems that may potentially run afoul of S8(b); devices or mechanisms that supersede or replace the pedestrian alert sound may also be found non-compliant.

NHTSA believes that the Superhorn, as it is described in your correspondence, does not conflict with S8(b). From your description, the pedestrian alert would continue to play the same set of sounds unaltered and concurrent with the Superhorn for the duration of horn control actuation. As you noted, the Superhorn has the potential to mask the pedestrian alert, in much the same way as a traditional horn may mask a pedestrian alert. However, the pedestrian alert would be masked with a trumpet sound resembling the tone, pitch, and loudness of a traditional car horn and only while the Superhorn sounds. Trumpet horn sounds are distinctive and recognized as a warning to pedestrians and other road users of an imminent hazard such as a vehicle collision.
The agency does not view masking under these described circumstances as problematic and believes that the proposed Superhorn would not alter the pedestrian alert or impair the detectability or recognition of a covered vehicle within the meaning of S8(b).

NHTSA notes that this interpretation is based on the description of the Superhorn you provided. If the Superhorn’s performance varies in any way materially from the description you provided, this interpretation will no longer be applicable. For example, if the Superhorn played in the absence of continuous horn control actuation, played for a longer duration, played a sound that made vehicles less identifiable as a vehicle, or disabled the pedestrian alert sound, then the feature would likely be deemed a device that alters, disables, or replaces the pedestrian alert in contravention of S8(b) or a pedestrian alert subject to the Sameness requirement in S5.5.

I hope this information is helpful. If you have any further questions, please feel free to contact Paul Connet of my staff at this address or at (202) 366-5547.

Sincerely,

John Donaldson 
Acting Chief Counsel

1 Pub. L. No. 111-373, 141 Stat. 4086 (Jan. 4, 2011).

2 Hybrid and electric vehicles are not required to have a dedicated pedestrian alert sound; vehicles that produce sufficient sound to meet the performance requirements described by S5.1-S5.4 may satisfy the requirements of FMVSS no. 141 without a dedicated alert system. See 81 FR 90416, 90450 (Dec. 14, 2016).
3 FMVSS 141 does not regulate other vehicle sounds besides the pedestrian alert system, but the test procedures do control for them. S7.1.2(a) specifies that measurements containing “any distinct, transient, loud sounds (e.g., chirping birds, overhead planes, trains, car doors being slammed, etc.) are considered invalid.” The same paragraph states that “[m]easurements that contain sounds emitted by any vehicle system that is automatically activated and constantly engaged during the entire 10 second performance test are considered valid.” Similar language conveying the same concepts is used as S7.3.2(a).
4 See PSEA § 3(2).
5 81 FR 90416, 90476 (Dec. 14, 2016).

6 See PSEA § 3(2).
7 78 FR 2798, 2834 (Jan. 14, 2013).
8 83 FR 8182, 8190 (Feb. 26, 2018).

Dated: 9/13/23

Ref: Standard No. 141