[Quietcars] NHTSA report: DOT HS 811 204 September 2009

Thu Oct 1 18:23:19 UTC 2009

Again, thanks for this.  Inconclusive or inclusive?  Since hybrid sales are
somewhere around 20% of the vehicles or less that are sold, we may find that
these stats will rise as the quieter, not specifically hybrid v3ehicles are
sold more readily or in greater numbers.  The beeping bulbs, as I call them,
would surely make a difference in alerting those of us who are pedestrians
as to which directions the cars are turning:  but there again, would the
noises emitted be the same for right or left turns, or if the bulbs were
utilized in the tail lamp areas, would they be of a di9fferent noise, note
or sound?  

Perhaps, the frequency of the beeps, meaning rapidity or speed, might be
different, but then again, which standards will be applied and by which
manufacturers and if the bulbs were installed by someone in an aftermarket
situation, who would monitor such installs?  All questions which are yet to
be answered.  Some might say that these are minor or trivial, but as someone
who is out daily and who also loves cars, these are things about which I've
thought just on the spur of the moment after reading your piece, bob.  

Mike T in NJ.

-----Original Message-----
From: quietcars-bounces at nfbnet.org [mailto:quietcars-bounces at nfbnet.org] On
Behalf Of Robert Wilson
Sent: Thursday, October 01, 2009 11:39 AM
To: quietcars at nfbnet.org
Subject: [Quietcars] NHTSA report: DOT HS 811 204 September 2009

The National Highway Traffic Safety Administration (NHTSA) released
"Incident of Pedestrian and Bicyclists Crashes by Hybrid Electric Passenger
Vehicles" a technical report that can be downloaded. We've looked at this
report and I would recommend anyone with an interest in this subject to get
a copy from:

http://www-nrd.nhtsa.dot.gov/Pubs/811204.PDF

This study is based upon looking at all accident data, not just fatalities,
in the years 2000-2007 from 12 states that to a greater or lessor extent
record accident. It is a fine report and includes the necessary disclaimers
about the low numbers of hybrid electric vehicle (HEV) versus Internal
Combustion Engine (ICE) vehicle accident data. But this is how it looks to
us.

The critical data are located in tables 6a "Vehicle maneuver prior to
pedestrian crashes HEVs and ICE vehicles" and 3d "Vehicle maneuver prior to
crash." It wasn't clear from the language but the number of accidents in
table 6a are divided by the number of maneuvers in table 3d. This generated
the "Incident rate of pedestrian crashes" for both HEV and ICE vehicles.

Now table 6a shows two areas where the distribution within either HEV or ICE
vehicles differ:

a.) Making a turn - 19 events or 1.8% HEV vs. 698 or 1.0% ICE
b.) Backing - 7 events or 5.3% HEV vs. 261 or 2.9% ICE

What these numbers discuss is the distribution of accident maneuvers within
each group, HEV or ICE vehicles, and there is a difference. In the case of
the 7 backing events, they did not flag that as statistically significant.
That they tagged the 19 turning events as significant is a little too close
call for my taste but the 1,061 records in table 3d is large enough. They
only had 132 backing accident records and having 7 events makes calling this
statistically import. For example, consider what happens if the number of
backing events changes by +/- 1:

6 events = 4.5%
7 events = 5.3%
8 events = 6.0%

A single backup event makes a substantial change in the percentage, which is
why more data, as is called out in the report, is important. But table 3d
"Vehicle maneuver prior to crash" carries and importance not really
addressed in the report.

The "Vehicle maneuver prior to crash" data breaks down the percentages of
maneuvers for both HEV and ICE vehicles and the two of interest, "Making a
turn" and "Backing" are 15% of all HEV maneuvers:

"Making a turn" - 13%
"Backing" - 2%

In fact "Going straight", the single largest source of accident data had all
but identical percentages for HEV, 9%, and ICE vehicles, 8%. Yet "Going
straight" is 44% for HEV and 47% for ICE vehicles ... in absolute terms, the
HEVs are less likely than an ICE vehicle to have a "Going straight" accident
in this 12 state, 2000-2007 data.

What this report tells us is only 15% of all HEV maneuvers have any
difference between HEV and ICE vehicles and the largest, 13%, occur while
turning. Upon reflection, this makes sense especially if we can get left and
right turn data rates.

In the USA, we drive on the right hand side of the road and right-turn on
red after stop is all but universal. So when a vehicle approaches a stop
light and plans to make a right turn, the driver looks to the left for
on-coming traffic and then switches to looking to the curb and then turning
right to make their turn. 

A pedestrian on the curb may also be looking to the left at on-coming
traffic and then decide to step out (aka. jay walk) but change their
attention to getting off the curb and the far side of the road. The
pedestrian can move faster than the car can react especially if crowds or
the car some 6-8 ft. behind the crosswalk, is not seen by the pedestrian.
Even with the turn signal on, only the driver has the audio 'click click' in
the cabin, there is no external 'click click' to alert anyone that the car
intends to make a left turn and should be watched by the pedestrians. This
problem is compounded for those with limited or no sight.

The paper calls out for more data and it occurs to me there is a natural lab
already out there ... hybrid electric taxi cabs in New York and California
cities. These mix of Prius and Ford Escape Hybrids are a natural lab and it
would relatively easy to install digitial video recorders that save the
window around every left and right hand turn. Then equip half of the
vehicles with audio alerting, external turn signals. There are after-market
backup lights that have a standard socket that should be able to replace the
turn signal lights and generate an external noise. Then run the experiment
for 6 months.

This type of experiment would provide turning incident, video records so
both close calls and accidents can be tracked and analyzed. The Japanese and
some USA universities have used similar video recording to gather data like
this before.

I do have a couple of concerns about this report and believe it needs to be
revised. Having gotten the accident data from 12 states, the HEV and ICE
vehicle registrations were not tabulated to give us an absolute risk factor
either by vehicle type or miles per vehicle type. This is important because
if HEV vehicles have say half the rate of accidents as ICE vehicles, then it
means the other 85% of accident types are half the rate for HEV vehicles
compared to ICE vehicles and the "Making a turn" and "Backing" accident
rates are identical between the HEV and ICE vehicles. Also, I would like to
see 'right turn' versus 'left turn' numbers, if it is available in the data.
My speculation is the 'right turn' case is likely to be the one needing
attention and perhaps only right-turn signal noise alerts are needed for
both HEV and ICE vehicles.

I do recommend this report and reading the data tables. There is quality
data here and it provides a roadmap to where investigations need to go next.

Thanks,
Bob Wilson

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