Page 22 - Winter 2020

ALERTING PEDESTRIANS BY SOUND
the minimum sound level emitted from a vehicle that is necessary to enable visually impaired pedestrians to reasonably recognize a nearby EV as a vehicle in operation while at the same time considering the overall community noise impact (PSEA, 2011).
In the 2013, the European Parliament and the Council of the European Union (EU) demanded that manufacturers include acoustic vehicle alerting systems (AVASs) in vehicles so that vulnerable pedestrians would be aware of the presence of an operating vehicle (European Parliament, 2013). In 2014, the EU agreed on mandating all manufacturers to install AVASs and set deadlines for their mandatory installation in all new EVs (EU, 2014). The content of this regulation was later reviewed to include more detailed requirements on AVAS performance (EU, 2017).
In 2017, the UNECE published uniform provisions concerning approval of quiet vehicles with regard to their reduced audibility. It defined
that any alert signal should
be a continuous sound that easily notifies pedestrians of an approaching vehicle (UNECE, 2017). In detail, AVAS mean a component or set of components installed in vehicles with the primary purpose of fulfilling the alert sound regulation requirements (UNECE, 2017).
It is worth mentioning that the first NHTSA
was reduced in the final rule to either four or two bands (Federal Motor Vehicle Safety Standards [FMVSS]; 2016). Similarly, the option of including a pause switch so drivers could disengage the AVAS was permitted in the European Regulation No. 540 (EU, 2014) but banned in the UNECE regulation (UNECE, 2017). These examples illustrate the ongoing need for modifications of alert- sound specifications in standards and regulations.
Regulations for Alert Signals
Today, several regulations exist to manage requirements regarding the audibility of EVs. In the United States, FMVSS No. 141 (2016) defines the minimum sound requirements for HEVs and EVs. For the European Union, United Nations Regulation No. 138.01 covering uniform provisions for approval of quiet road transport vehicles with regard to their reduced audibility regulates the alert-sound requirement. There are similar national regulations in many other countries, including Japan and China, based on UNECE R138.01 (2017). As a
Table 1. Center frequencies and sound pressure levels for four-band alert signals
One-Third Octave-Band Center Frequency (Hz)
Minimum A-Weighted SPLs (dB)
Example of Measured Alert Signal
315
52
48
400
51
52*
500
52
49
630
53
55*
800
53
51
1,000
54
52
1,250
54
55*
1,600
51
49
2,000
51
48
2,500
50
51*
3,150
47
44
4,000
45
43
5,000
43
41
One-third octave-band center frequencies and minimum A-weighted sound pressure levels (SPLs) for four-band alert signals are shown for the condition “constant vehicle pass-by speeds equal or greater than 20 km/h but less than 30 km/h” as defined in Federal Motor Vehicle Safety Standards (FMVSS) No. 141. *Example of a measured alert signal meeting the minimum level requirements of FMVSS No. 141 due to the one-third octave bands.
notice of
rulemaking
regarding
sound requirements for HEVs and EVs in 2013 was “overengineered.”
As a consequence, the initial NPRM proposal of minimum level thresholds in eight one-third octave bands (NHTSA, 2013)
proposed (NPRM) minimum
22 Acoustics Today • Winter 2020