Quieter Cars and the Safety Of Blind Pedestrians

DOT HS 811 304 April 2010

"Quieter Cars and the Safety Of Blind Pedestrians: Phase I", NHTSA

The first, private tests sponsored by the NFB had mixed results and dubious methodology. For example, the tires were not checked to make sure they were uniformly new versus worn. In these tests, tire state was checked. Regardless, the NHTSA decided to replicate the earlier tests and this 151 page report covers the details:

The results varied with the hybrids detected sometimes before their "ICE" equivalent. No wonder this report didn't receive a lot of public view . . . it is not a slam-dunk for the "Bell the Hybrid" crowd.

Bob Wilson

 

I've only taken less than 30 minutes to scan the report that can be downloaded from here. To throughly understand every aspect, I'll have to print a copy and make notes. But I got the impression blind and sighted test subjects were used and in large enough numbers to be a valid test.

Now one caution is the sound units are listed in decibels, a scale not familiar to many folks. As a general rule of thumb:

• +3 decibels ~= 2 times the audio power
• -3 decibels ~= 1/2 the audio power

But before trying to really understand the report, it makes a lot of sense for a report reader to review the physics and physiology: dB: What is a decibel?

One late thought, when I write up my review, I'll convert SAE units to meters and km/h. I can fully understand the problem of one style units ... another good reason for working from a hardcopy.

I've only done a cursory review, looking at the conclusion, and so far, it looks like a well done study that paid attention to the variables. Regardless, they used a Toyota Matrix as the alternative to the Toyota Prius and I'd like to check the specifications. Good Prius friend Hobbit will be happy to see their report detected the relatively higher noises of the ZVW30 Prius.

I noticed that backing up, our hybrids were reported as harder to detect. This is something I agree with in criticizing the "backup beep" that is in the cabin instead of coming from the backup lights. I didn't see, yet, where they discussed dealing with the backup, cabin beep. Regardless, I've already bought some backup lights that have an audio alarm and plan to test them in our Prius and possibly in the turn signal lights. BTW, Consumer Reports has also criticized the absence of external, backup audio alarms in all vehicles.

You' all need to understand that my opposition to "Bell the Hybrid" is based upon the absence of credible, significant risks but that does not mean they are risk free! It is important to read every credible paper and understand what is being presented. No one has to 'make stuff up' but simply point out the obvious.

Bob Wilson

ps. "I never gave anybody hell. I just told the truth and they think it's hell" - H. Truman

 

The five page "Executive Summary" condenses the report and reveals:

• Toyota Matrix as analog to Prius - I checked the Edmunds specifications and was impressed by how closely these cars come. We're used to seeing the Corolla used as the non-hybrid, gas analog but it has always been a terribly poor choice. But the Matrix, classified as a small wagon, is about as close to a 2010 Prius as one can come. Good choice! (pp. 2.)
• 5 kHz Prius regeneration noise - some of us knew the 2010 Prius was louder than the 1.5L Prius (Hobbit reported this from last year's Hybridfest) and the 5 kHz, audio signal during braking posed a real challenge to the study. I got the impression they didn't expect it and it changed the expected results in a way that could not be ignored (pp. 4.)
• (UNDOCUMENTED) no need to legislate a study - one of the claims for the "Bell the Hybrid" legislation had been 'this is needed to authorize a study.' The existence of this report belies this claim. The NHTSA never needed a law to do their job, study vehicle safety. They might have needed a budget item, but legislation to authorize a study has never been needed. This leaves only one justification, to "Bell the Hybrid" (aka. give them a fair trial before we hang 'em.)
• Blind advocacy groups dictated one claim - starting with "At the present time, only countermeasures that generate alert sounds emulating those of approaching ICE vehicles . . . " is embedded in the paragraph, pp. 4-5. This could have been lifted from statements found in the June 23, 2008 NHTSA hearing from the blind advocacy groups. This one section eviscerates any "honest broker" standing of the report. It could have been included in other sections but within the "Executive Summary" it shows the NHTSA as being less than fair and impartial.
• Testing in pristine, 31.2 dB(A) and 49.8 dB(A) ambient - this may be covered in the body of the report but the executive summary fails to explain why these are representative values. I know, a minor nit, but it is something of interest.
• Prius and five other cars - the study included the Highlander and Honda Civic hybrids, yet the Prius received substantially more attention. Then the Prius 5 kHz regenerative audio signal 'spoiled the party.'

There are 70 pages remaining that cover the details and half-again more appendices and bibliography. But the Executive Summary pretty well follows the same pattern seen first in the June 23, 2008 NHTSA hearing. Sad to say but this effort by the blind advocates within the NHTSA is poisionous to NHTSA credibility and that is a deadly shame.

Bob Wilson

ps. It looks like they had about 50 blind test subjects and mixed results.