fires than vans registered in sun belt states. Vans registered in salt belt states are about 40
percent less likely to have a MHE fire than a van from the sun belt states. A total of 141
vans from the salt belt states experienced a fire. There were 79 crashes involving a van
from the sun belt states that had a fire. There were 29 vans from the salt belt states and sun
belt states, which were identified as having a fire as the MHE. Exhibits 69 and 70 contain
the results.

Exhibit 69
SALT EFFECT - VANS

Salt Vans Number Percent Number Percent

Status in Fatal Fire Fire MHEF MHEF
Crashes Vans Vans Vans Vans
Salt Belt 7420 141 1.90 29
Sun Belt 4312 79 1.83 29
Other | 5702 127 2.23 45
Exhibit 70

95 PERCENT CONFIDENCE LIMITS FOR SALT EFFECT - VANS

Lower Percent Upper Lower Percent | ee |

Limit Fire Limit Limit MHEF Limit
Salt Belt 1.59 1.90 2.21 0.25 | 0.39 0.53
Sun Belt 1.43 1.83 2.23 0.43 0.67 0.92

Other 1.84 2.23 2.61 0.56 0.79 1.02 |

Fatality Estimates Due to Fire

The cause of death is often not clear cut. FARS data are used to compute estimates of
fatalities due to fire occurrence, and lower and upper bounds of fatalities due to fire. A
fatality is counted if the fatality occurred in a model year 1978 or newer car, truck, or van
from 1979 to 1992. The apparent increase in the number of fatalities over time may in part
be due to the increasing number of 1978 and later model year vehicles, as well as, the
general increase in vehicle miles traveled. In addition to the numbers of fatalities, the
percentage of total occupant fatalities associated with fire is also presented.

The number of deaths caused by fire was estimated and appears in Exhibit 71. The
underlying assumption of Exhibit 71 is that if the most harmful event field is coded as fire,
then at least one death in that vehicle was caused by fire. This provides the estimate of the
minimum number of fatalities. The most harmful event (MHE) estimate assumes that all
deaths within a vehicle coded as a most harmful event fire were due to fire. If the most
harmful event field is coded as anything other than fire then at least one individual in the
crash died of a cause other than fire, but the other fatalities, if there were more than one

- 52-


Exhibit 56

95 PERCENT CONFIDENCE LIMITS FOR ROLLOVER - LIGHT TRUCKS

Rollover Lower | Percent Upper Lower | Percent Upper
Status Limit Fire Limit Limit MHEF Limit

Rollover 2.35 2.57 2.79 0.76 0.89 1.02

No Rollover 2.51 2.64 2.77 0.82 0.89 0.97

Vans that experienced a rollover have a higher rate of occurrence of fires/MHE fires by
approximately 50 percent. A total of 85 vans experienced a rollover and had a fire. There
were 271 vans that had a fire but did not experience a rollover. There were 25 vans that
experienced rollovers that were also identified as having a fire as the MHE. A total of 81
vans did not experience a rollover and were identified as having a fire as the MHE. Exhibits

57 and 58 contain the results.

Exhibit 57
ROLLOVER - VANS
Rollover Vans Number Percent Number Percent
Status in Fatal Fire Fire MHEF MHEF
Crashes Vans Vans Vans Vans
Rollover 3021 85 2.81 25 0.83
No Rollover 14898 271 1.82 81 0.64
Exhibit 58
95 PERCENT CONFIDENCE LIMITS FOR ROLLOVER - VANS
Rollover 1 Lower Percent Upper Lower Percent Upper
Status Limit Fire Limit Limit MHEF Limit
Rollover 2.22 2.81 3.41 0.51 0.83 LAS
No Rollover 1.60 1.82 2.04 0.42 0.54 0.66

-43-



Technical Report Documentation Page

T. Report No 2. Government Accession No. 3. Recipient's Caralog No.

DOT HS 808 208

4 Title and Subutle 5. Report Dare
An Analysis of Fires in Passenger Cars, Light December 1994
Trucks, and Vans 6. Perla - >

la Performing Organization Report No.

7. Author! s}

Tessmer, Joseph

9, Pesforming Organization Name and Address TO" Work Unit No. (TRAIS)
Mathematical Analysis Division
National Center for Statistics and Analysis TI. Contract or Gront No.
400 7th Street SW
Washington, DC 20590 13.” Type of Report and Period Covered
12. Sponsoring Agency Name ond Address
Research and Development NHTSA Technical Report
National Hwy Traffic Safety Administration
400 7th Street SW [T4- Sponsoring Agency Code

Washington, D.C. 20590

15. Supplementary Notes

16. Abstract

This report contains an analysis of historical data on fire
occurrence in fatal and less serious crashes as a function of
crash, vehicle, and driver characteristics that influence the
likelihood of postcollision vehicle fires.

The report is organized into four sections. Data on the vehicles
included in the study are for 1978 and later model years. The
first two sections use 1979 thru 1992 data from the Fatal
Accident Reporting System (FARS). The first section contains raw
cross tabulations of the data. The second section constructs
multivariate statistical models. Section three examines raw
cross tabulations of data from the State of Michigan from 1982 to
1991. The Michigan police accident report (PAR) collects data on
fuel leaks which are used to estimate the relationship between
fires and fuel leaks. Section four is based on the National
Accident Sampling System Crashworthiness Data System (NASS CDS)
for burn injuries from 1988 to 1993.

17. Key Words 18, Distribution Statement
Document is available to the public
Fire Occurrence, Fuel System, through the National Technical
Integrity, Fuel Leaks Information Service.

Springfield, VA 22161

19. Security Clossif, (of this report) 20. Security Classil. (of this page) 21. Ne. of Pages | 22. Price

Unclassified Unclassified 97
Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized


Exhibit 76
BASE MODEL FIRE ODDS RATIO WITH
LOWER AND UPPER 95 PERCENT CONFIDENCE LIMITS?

—=
[ Variable Lower 95% Odds Upper 95%
Limit Ratio ¥ Limit

Vehicle age 1.019 1.026 | 1.032 |
Vehicle type
Truck vs. Car 1.021 1.075 ia |
Van vs. Car 0.321 0.975 2.962
Age of driver 2a 0.990 0.991 0.993
Night vs. Day 1.464 1,531 1.602
Speed limit 1.033 1.035 1.038
Multiple-vehicle 0.723 0.807 0.902
Area of damage
Rear - 1,968 2.157 2.364
: Front 1.015 1.073 1.134
Side 0.775 0.832 0.894
Object struck
Vehicle 3.907 4.541 5.278
Narrow 7.007 7.931 8.977
Fixed 5.494 6.217 7.036
Overturn 1.515 1.78 | 2.092

When comparing cars, light trucks, and vans, i.e., the second, fourth and fifth columns of
Exhibit 75, one may compare a variable (row) at a time. As a rough approximation, to
determine if the coefficients are significantly different from those of the base model, the
upper and lower 95 percent confidence limits, for the variable fire, were calculated. The
results of these calculations are in Exhibit 76.

In general, if an estimated odds ratio for a comparison model is within the 95 percent
confidence level then one can conclude that there is no measurable difference in the
coefficients (although to be certain, the complete statistical test, incorporating the standard

2 Hosmer, David W. and Lemeshow, Stanley, Applied Logistic Regression, New York:
John Wiley & Sons, Inc., 1989, Chapter 3 p. 44.

- 61 -


numbers and percentage rates of fire for the sum of personal injuries and property damage
crashes which make up the police reported crashes. Combining the data results in estimates
of rate of fires that are bounded above and below by the two sets of data, that is the results
will be between the other two estimates. In addition, since the crashes have been pooled, the
confidence intervals will be tighter. The results are found in Exhibits 86, 87 and 88. The
combined data, however, does not provide any information on fires with respect to the
severity of the crash. Usually crashes that produced personal injury were more severe than
crashes that did not and have a higher fire rate. The results show that there were a total of
6024 cars that had either a fire or a fire and a fuel leak out of 3,410,645 reported crashes.
This results in an overall fire rate of 0.18 percent.

Exhibit 86
MICHIGAN FREQUENCY POINT OF IMPACT
ALL REPORTED CRASHES - CARS

Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire
Front [ 6402 2374 621 1934545
Rear 3525 654 227 847928
Side 1711 431 138 483048
Other 2383 1409 170 125079
Exhibit 87

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
ALL REPORTED CRASHES - CARS

Leak Fire Leak & No Leak

Only Only Fire No Fire
0.33 0.12 | 0.03 99.52
0.41 0.08 0.03 99.48
0.35 0.09 0.03 99.53
1.85 1.09 0.13 96.93}

-T2-


There is no appreciable increase or decrease of fires/MHE fires for vans with increasing age.
Due to the small sample sizes, the rates are quite variable. The results are in Exhibits 19

and 20.
Exhibit 19
VEHICLE AGE in YEARS - 1978 MODEL YEAR AND LATER VANS
Van Vans Number Percent Number Percent
Age in Fatal Fire Fire MHEF MHEF
Years Crashes Vans Vans Vans Vans
0 2316 45 1.94 8 0.35
1 3154 57 1.81 14 0.44
2 2676 52 1,94 22 0.82
3 2112 38 1.80 Il 0.52
4 1739 36 2.07 7 0.40
5 1367 24 1.76 5 0.37
6 1159 25 2.16 12 1.04
7 924 17 1.84 6 0.65
8 663 15 2.26 6 0.90
9 559 18 3.22 7 1.25
10 385 13 3.39 4 1.04
11 324 5 1.54 1 0.31
12 256 3 1.17 1 0.39
13 188 7 3.72 2 1.06
14 98 1 1,02 0 0.00

-23-



of different vehicle types in slightly different ways. Cars, with an odds ratio of ¥ = 0.521,
are the most sensitive to the number of vehicles involved in the crash. Light trucks, with an
odds ratio of ¥ = 0.651, are least sensitive and vans, with an odds ratio of ¥ = 0.589, are
between cars and light trucks. A crash of a van involving no other vehicle vs. a crash of a
car involving no other vehicle is 12.4 percent [{(0.586/0.521) = 1.124] -1}*100] more likely
to have a MHE fire than a multiple-vehicle van crash vs. a multiple-vehicle car crash. A
crash of a truck involving no other vehicle vs. a crash of a car involving no other vehicle is
24.9 percent [{(0.651/0.521) = 1.249 -1}*100] more likely to have a MHE fire than a
multiple-vehicle truck crash vs. a multiple-vehicle car crash.

The area of damage, i.c., the location of damage (rear, front, or side) seems to produce
different rates of MHE fire across vehicle types. Cars, with an odds ratio of ¥ = 2.068 for
damage to the rear, are more sensitive than light trucks W = 0.588, and vans ¥ = 1.432 for
damage to the rear. A car with damage to the rear in a fatal crash is 44.4 percent,
[{(2.068/1.432) = 1.444 -1}*100], more likely to have a MHE fire than a van with damage
to the rear in a fatal crash. A car with damage to the rear in a fatal crash is 251.7 percent
[{(2.068/0.588) = 3.517 -1}*100] more likely to have a MHE fire than a truck with damage
to the rear in a fatal crash.

Cars, with an odds ratio of ¥ = 0.471, for damage to the front, are relatively less likely to
have a MHE fire than light trucks with an odds ratio of ¥ = 0.676, or vans with an odds
ratio of ¥ = 0.936 for damage to the front. A van receiving frontal damage in a fatal crash
is 98.7 percent [{(0.936/0.471) = 1.987 -1}*100] more likely to have a MHE fire than a
frontally damaged car. A frontally damaged truck in a fatal crash is 86.1 percent
[{(0.936/0.471) = 1.861 -1}*100] more likely to have a MHE fire than a frontally damaged
car.

Cars, with an odds ratio of ¥ = 0.339 for damage to the side, are relatively less likely to
have a MHE fire than light trucks with an odds ratio of Y = 0.624, or vans with an odds
ratio of % = 0.912 for damage to the side. A side-damaged van in a fatal crash is 46.2
percent [{(0.912/0.624) = 1.462 -1}*100] more likely to have a MHE fire than a side-
damaged car. A truck with damage to the side, which is involved in a fatal crash is 84.1
percent [{(0.624/0.339) = 1.841 -1}*100] more likely to have a MHE fire than a car, with
damage to the side, which is involved in a fatal crash.

To examine the effect of the type of object struck on MHE fire, the objects have been
partitioned into categories; vehicle, narrow, fixed, and overturn; across vehicle types. Note
that cars, with an odds ratio of ¥ = 5.964 are more likely to have a MHE fire following
striking a vehicle, than light trucks with an odds ratio of ¥ = 5.061, or vans with an odds
ratio of & = 2.565. A car that struck a vehicle in a fatal crash is 132.5 percent
[{(5.964/2.565) = 2.325 -1}*100] more likely to have a MHE fire than a van, which struck
another vehicle. A car that struck another vehicle in a fatal crash is 17.8 percent
[{(5.964/5.061) = 1.178 -1}*100] more likely to have a MHE fire than a truck that struck a
vehicle.

Cars, with an odds ratio of ¥ = 10.207 are relatively less likely to have a MHE fire if they
strike a narrow object such as a telephone pole than light trucks with an odds ratio of ¥ =
14.249, or vans with an odds ratio of ¥ = 12.890. A van that struck a narrow object in a
fatal crash is 26.3 percent [{(12.890/10.207/) = 1.263] -1}*100] more likely to have a MHE

- 67-


Base Models for Fire/MHE Fire

Exhibit 74 contains the odds ratio and the p values for the base models for fire and MHE
fire.

Exhibit 74
BASE MODEL FOR FIRE AND MHE FIRE

Variable Odds p Odds p
Ratio Fire Ratio MHEF
Fire ¥ MHEF ¥
Vehicle age 1.026 0.0001 | N/A N/A
Model year N/A N/A 0.970 0.0001
Vehicle type
Truck vs. Car 1.075 0.0001 1.351 0.0001
Van vs. Car 0.975 0.2281 1.133 0.2758
Age of driver 0,991 0.0001 0.992 0.0001
Night vs. Day 1.531 0.0001 1,731 0.0001
Speed limit 1.035 0.0001 1.042 0.0001
Multiple-vehicle 0.807 0.0001 0.542 0.0001
Area of damage
Rollover || N/A N/A 0.414 0.0001
Rear 2.157 0.0001 1.796 0.0001
Front 1.073 0.0128 0.527 0.0001
Side 0.832 0.0001 0.394 0.0001
Object struck
Vehicle 4.541 0.0001 5.57 0.0001
Narrow 7.931 0.0001 11.28 0.0001
Fixed 6.217 0.0001 9,122 0.0001
[ vena | 1.780 0.0001 2.290 0.0001

Vehicle age is included as a variable when modeling the occurrence of a fire but is not
included when modeling MHE fire since it is not statistically significant. For the same
reason, model year and rollover are not included when modeling fire but are included when
modeling MHE fire. For both fire and MHE fire, the truck vs. car dichotomous variable is

-57-


Conclusions and Recommendations

The rate of postcollision fires in fatal 1978 or newer car crashes for the United States from
1979 to 1992 averages 2.42 percent (Exhibit 21). The rate of postcollision fires in fatal 1978
or newer car crashes in Michigan from 1982 to 1991 averages 4.30 percent (Exhibit 107).
The rate of postcollision fires in all 1978 or newer car crashes in Michigan from 1982 to
1991 averages 0.18 percent (Exhibit 86).

Based on data from the Fatal Accident Reporting System (FARS) it is estimated that 2700
deaths were due to a fire in a 1978 or newer car truck or van. If all deaths, in vehicles
coded as most harmful event fire are included the total rises to 3557. The maximum number
of possible deaths due to fire is calculated to be 4973. On an annual basis, over the last
three years, this is approximately 261, 340, and 490 deaths due to fire per year depending on
the measure used (Exhibit 71). Under similar conditions, NASS estimates that there are
approximately 670 bum injuries per year. Since 1979 there has been a slight decline in the
percent of deaths due to fire compared to the total number of deaths in 1978 or newer model
cars, trucks and vans (Exhibit 72).

The vehicle age of cars has a statistically significant effect on fire. The results show that as
cars age they are more likely to have a fire (Exhibits 15 and 117).

The rate of fire and MHE fire for rollover and cars with damage to the rear shows
substantial variation by weight class. Rollovers, of weight class 5, have the highest rate for
fire 5.33 percent and MHE fire 2.08 percent. Cars with damage to the rear of weight class
4 have the highest rate of fire 6.16 percent and MHE fire 2.62 percent (Exhibits 33 and 35).

Light trucks are more susceptible to fires than are cars or vans. However, there are
approximately 3 times as many fires in cars as in light trucks. Over the period of the study,
1979 through 1992, 6854/2054 cars, 2280/775 light trucks and 356/106 vans had fires/MHE
fires, The increasing popularity of the passenger minivan during the study period is expected
to continue. This may lead to increasing incidents of fires within the van category (Exhibits
12, 23, and 25).

Higher posted speed limits are associated with increased rates of fire/MHE fire. An increase
in the posted speed limit of ten mph raises the incidence of fire/MHE fire by 41.1 percent
and 50.9 percent, respectively. Raising the speed limit from 30 mph to 55 mph (an increase
of 25 mph) raises the likelihood of a fire/MHE fire in a fatal crash by 136.3 percent (more
than double) and 179.7 percent (more than double), respectively (Exhibit 74). An increase in
the speed limit from 30 mph to 65 mph raises the likelihood of a fire/MHE fire, in a fatal
crash, by 233.4 percent (more than triple) and 322.1 percent (more than quadruple). While
posted speed limit does not necessarily indicate actual travel speeds, it is nonetheless a
surrogate measure of travel speed, and an important predictor of the likelihood of
Postcollision fire.

The area of damage, i.e., the principal area where the vehicle was struck, has a statistically
significant effect on the rate of fire/MHE fire. Cars are more suspectable to this factor than
are light trucks and vans, presumably due to the location of the fuel tank, generally in the
rear. If a car involved in a fatal crash is struck in the rear, it is approximately 140 percent
and 340 percent more likely to have a fire/MHE fire, respectively, than a car with damage

- 96 -


Exhibit 83
MICHIGAN FREQUENCY POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire
Front | 2715 1341 335 1573796
Rear 1559 491 129 678976
Side 541 261 66 383066
Other 1066 1256 114 78871_ |
Exhibit 84

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire
Front 0.17 0.08 0.02 99.72
Rear 0.23 0.07 0.02 99.68
Side 0.14 0.07 0.02 99.77
L Other 1.31 1.54 0.14 97.00
Exhibit 85

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

tmp | Low % | Up Low % Up Low Fire Up
Area || Lim | Leak | Lim Lim | Fire | Lim Lim | Leak Lim
Front | 0.17 0.17 | 0.18 0.08 | 0.08 | 0.09 0.02 | 0.02 0.02
Rear |} 0.22 | 0.23 | 0.24 0.07 | 0.07 | 0.08 0.02 | 0.02 0.02
Side | 0.13 | 0.14 | 0.15 0.06 | 0.07 | 0.08 0.01 | 0.02 0.02
{__Other | 1.23 1.31 | 1.39 1.46 | 1.54 | 1.63 0.11 | 0.14 0.17

The data of the last six exhibits can be combined to provide estimates of fires for both
personal injury and property damage only crashes. When this is done one can report on the

-71-


Base Models for Fire/MHE Fire

Exhibit 74 contains the odds ratio and the p values for the base models for fire and MHE

fire.

Exhibit 74
BASE MODEL FOR FIRE AND MHE FIRE

[ Variable Odds Pp Odds P
Ratio Fire Ratio MHEF
Fire ¥ MHEEF ¥
Vehicle age a0 1.026 0.0001 | N/A N/A _|
| Model year N/A N/A 0.970 0.0001
Vehicle type
Truck vs. Car 1.075 0.0001 1.351 0.0001 :
Van vs. Car 0.975 0.2281 1.133 0.2758
Age of driver 0.991 0.0001 0.992 0.0001
Night vs. Day 1.531 0.0001 1.731 0.0001
Speed limit 1.035 0.0001 1.042 0.0001
Multiple-vehicle 0.807 0.0001 0.542 0.0001
Area of damage
Rollover |} N/A N/A 0.414 0.0001
Rear 2,157 0.0001 1.796 0.0001
Front 1.073 0.0128 0.527 0.0001
Side 0.832 0.0001 0.394 0.0001
Object struck
Vehicle | 4.541 0.0001 5.57 0.0001
Narrow 7.931 0.0001 11.28 0.0001
Fixed 6.217 0.0001 9.122 0.0001
Overtum 1.780 0.0001 2.290 v0 |

Vehicle age is included as a variable when modeling the occurrence of a fire but is not
included when modeling MHE fire since it is not statistically significant. For the same
reason, model year and rollover are not included when modeling fire but are included when
modeling MHE fire. For both fire and MHE fire, the truck vs. car dichotomous variable is

-5

7 -


damage to the rear. A car with damage to the rear in a fatal crash is {(2.484/0.842 =
3.950] -1}*100 = 395.0 percent more likely to have a fire than a van with damage to the
rear in a fatal crash.

Cars, with an odds ratio of ¥ = 1.043, for damage to the front, are less sensitive than light
trucks ¥ = 1.175, and vans ¥ = 1.165 for damage to the front. A van receiving frontal
damage in a fatal crash is {[1.165/1.043 = 0.895] -1}*100 = 11.7 percent more likely to
have a fire than a frontally damaged car. A frontally damaged truck in a fatal crash is
{{1.175/1.043 = 1.127] -1}*100 = 12.6 percent more likely to have a fire than a frontally
damaged car.

Cars, with an odds ratio of ¥ = 0.790 for damage to the side, are less sensitive than light
trucks ¥ = 1.050, and vans ¥ = 1.074 for damage to the side. A side-damaged van in a
fatal crash is {{1.074/0.790 = 1.359] -1}*100 = 35.9 percent more likely to have a fire than
a side-damaged car. A truck with damage to the side, which is involved in a fatal crash is
{[1.050/0.790 = 1.329] -1}*100 = 32.9 percent more likely to have a fire than a car, with
damage to the side, which is involved in a fatal crash.

To examine the effect of the type of object struck, on dependent variable fire, the objects
have been partitioned into five categories: vehicle, narrow, fixed, overturn and other, across
vehicle types. Note that cars, with an odds ratio of ¥ = 4.946 for striking a vehicle, are
more sensitive than light trucks ¥ = 3.558, or vans Y = 3.455 for striking a vehicle. A car
that struck a vehicle in a fatal crash is {[4.946/3.455 = 1.432] -1}*100 = 43.2 percent more
likely to have a fire than a van, which struck another vehicle. A car that struck another
vehicle in a fatal crash is {[4.946/3.558 = 1.390] -1}*100 = 39.0 percent more likely to
have a fire than a truck that struck a vehicle.

Cars, with an odds ratio of Y = 8.024 for striking a narrow object such as a telephone pole,
are more sensitive than light trucks ¥ = 7.747, and vans ¥ = 7.451 for striking a narrow
object. A car that struck a narrow object in a fatal crash is {[8.024/7.451 = 1.077] -1}*100
= 7.7 percent more likely to have a fire than a van that struck a narrow object. A car that
struck a narrow object in a fatal crash is {[8.024/7.747 = 1.036] -1}"100 = 3.6 percent
more likely to have a fire than a truck, which struck a narrow object, which is involved in a
fatal crash.

Cars, with an odds ratio of ¥ = 6.661 for striking a fixed object such as a wall, are more
sensitive than light trucks ¥ = 5.116, and vans ¥ = 5.072 that struck a fixed object. A car
that struck a fixed object in a fatal crash is {[6.661/5.072 = 1.313] -1}*100 = 31.3 percent
more likely to have a fire than a van that struck a fixed object. A car that struck a fixed
object in a fatal crash is {[6.661/5.116 = 1.302] -1}*100 = 30.2 percent more likely to
have a fire than a truck that struck a fixed object.

- 63 -


Exhibit 75
BASE MODEL COMPARED TO VEHICLE SPECIFIC MODELS - FIRE

Odds Ratios
Variable af Base Cars Cars & Trucks Vans
Model ¥ Only © Weight ¥ Only ¥ Only ¥ |
Vehicle age 1.026 1.031 1.033 1.010 1.006
Vehicle type
Truck vs. Car 1.075 | Cars Cars & Trucks Vans
Van vs, Car 0.975 | Only Weight Only Only
Age of driver 0.991 0.991 0.991 0.992 0.993
Night vs. Day | 1.531 1.589 1,594 1,396 1,377
Speed limit 1.035 1,032 1.032 1.050 1.050
Multiple-vehicle 0.807 0.773 0.783 0.973 0.979
Car weight in =f N/A 1.000026 | N/A N/A
Area of damage
Rear 2.157 2.484 2.482 0.936 0.842
=| 1.073 1.043 1.033 1.175 1,165
Side 0.832 0.790 0.787 1.050 1.074
Object struck
Vehicle 4.541 4.946 4.952 3.558 3.455
Narrow 7.931 8.024 8.069 7.747 7.451
Fixed
Overturn

Within the Fatal Accident Reporting System (FARS) data on the weight of a car is collected.
These data are generally not available for light trucks and vans. The third column, headed
Cars & Weight, are the odds ratios for a model that contains the car weight as an additional
independent variable. The weight variable is virtually orthogonal to the vector space spanned
by the other variables and therefore there are only small changes between the sets of odds
ratios of the cars only model and the cars & weight model. An odds ratio of 1.000026 is the
change in the odds ratio for one additional pound of weight of a car. This means that the
odds ratio increases to (1.000026)'TM = 1.026 if the weight of a car is increased by 1000
pounds. That is, ceteris paribus, for every additional 1000 pounds of weight, a car is 2.6
percent more likely to have a fire in a fatal crash. Although the odds ratio is very close to
one (due to the scale of the weight variable) it is significantly different from 1 at the a =
0.0001 level.

- 60 -


to the front (Exhibit 75 and 77). Over the time period of the study, 1979 through 1992,
there were 3275/839 cases of fatal crashes where a car was struck in the front and had a
fire/MHE fire. During this period there were 640/270 cases where a car was struck in the
rear and had a fire/MHE fire (Exhibit 30). The data suggest that crash tests of cars should
include frontal crash tests to address the largest number of postcollision fires, and rear
crashes, to address the greatest likelihood of postcollision fires, as part of the testing
procedure.

The object that is struck by a vehicle involved in a fatal crash affects the likelihood of a
fire/MHE fire. Vehicles striking narrow objects, such as telephone poles, are more likely to
have a fire/MHE fire than vehicles striking other types of objects. In particular, a vehicle
striking a narrow object is 27.6 percent and 23.7 percent more likely to have a fire/MHE
fire, respectively, than vehicles that strike other fixed objects (Exhibit 74). However, there
are relatively few cases of a vehicle being struck in the rear by a narrow object, (see
Exhibits 46-51), i.e., both types of events occur, but usually not together.

The Michigan data show that car crashes involving injuries have a significantly higher rate of
fire than do crashes that only have property damage if the damage is to the front rear or side.
However, the situation is reversed for the "other" impact areas, which includes damage to
the under carriage (Exhibits 81 and 84).

Light truck in crashes with personal injury have a higher rate of fire with front impacts than
with side impacts (Exhibit 90).

The Michigan data was used to calculate the conditional probability of a fire given a fuel leak
to be 0.075 or 7.5 percent. However, fire was 52.8 times as likely if a fuel leak was
reported as opposed to when a fuel leak was not reported (Exhibit 116).

Most burn injuries, due to vehicle fires, occur in crashes with Delta V in excess of 20 mph
(Exhibit 122).

Virtually all fires that originate in the fuel system, rather than the engine compartment, are
major fires. If the origin of the fire is not the fuel system, this usually means the fire
originated in the engine compartment, then less than half of the fires are classified as major
fires (Exhibit 125).

-97 -


Exhibit 11

4

MICHIGAN NON-FATAL PERSONAL INJURY FIRE Crashes in VANS
by IMPACT AREA

Total Injury Number Lower 95% Percent Upper 95%
Crashes Fires Limit Fire Limit
——
9621 35 0.24 0.36 0.48
4778 6 0.03 0.13 0.23
2519 8 0.10 0.32 0.54
1934 13 0.31 0.67 1.04 |
Exhibit 115

MICHIGAN PROPERTY DAMAGE ONLY FIRE Crashes in VANS by IMPACT AREA

Impact Total Number Lower 95% Percent Upper 95 %
Crashes Fires Limit — | Fire Limit
Front 61662 69 0.09 0.11 0.14
37621 31 0.05 0.08 0.11
oe 16772 18 0.06 0.11 0.16
other | 4125 75 1.41 1.82 22 |

- 83 -


An apparent contradiction seems to exist when the Michigan fire rates of cars with a rear
impact area are compared to the similar results from the FARS analysis. To examine this
issue further, the fatal crashes in Michigan were examined, by themselves, by impact area.
As with the FARS data the rate of fire occurrence is about twice (8.59 percent [rear] vs.
4.98 percent [front]) the rate for a rear impact vs. a frontal impact (See Exhibit 30).
However, like FARS there are many more fires with front impacts compared to rear impacts,
in this case there are approximately six (6) times as many. Any apparent discrepancies
between the Michigan data and the FARS data are most likely due to the shorter time period
of the Michigan data 1982 to 1991 rather than 1979 to 1992 and or the single state of
Michigan, with possibly different coding procedures, rather than the combined fifty states
plus the District of Columbia. One would not expect the fire rates between Michigan and
FARS to be the same. However, the rate of fire occurrence for both Michigan and FARS is
considerably higher for rear impacts than for front impacts and both Michigan and FARS
have more crashes with damage to the front than any other area.

There were a total of 6229 car crashes in Michigan of which 268 had a fire. This produces

an average fire rate of 4.30 percent.

Exhibit 107
MICHIGAN FATAL FIRE Crashes in CARS by IMPACT AREA

| Impact Total Fatal Number Lower 95% Percent Upper 95%
Area Crashes Fires Limit Fire Limit
Front 3151 157 4.22 4,98 5.74
Rear 291 25 5.37 8.59 11.81
Side | 2124 69 2.49 3.25 4.00
Other | 663 17 1.36 2.56 3.77 |

One can also examine the rate of fire by severity of the crash. Michigan partitions data by
crashes that result in one or more fatalities, crashes that result in personal injury, but not a
fatality and property damage only crashes. Exhibits 107 thru 115 contain this information
for cars, trucks and vans. The front, rear, and side impact areas in general have the highest
rates of fire occurrence for fatal crashes, lower rates for personal injury crashes that do not
involve a fatality, and the lowest rate for crashes that only have property damage. Note that
the Michigan data for fatal crashes involving trucks and vans often have five or less
observations which experienced a fire. In such cases the estimates of the rates may be less
stable than rates based on more observations.

- 80 -


There was no appreciable relationship between the year of the crash on the rate of occurrence
of either fire or MHE fire for vans. Note that the sample size for vans is smaller than the
sample size for light trucks. The results are in Exhibits 5 and 6.

Exhibit 5
YEAR OF CRASH - 1978 MODEL YEAR AND LATER VANS
Year Vans Number Percent Number Percent
of in Fatal Fire Fire MHEF MHEF
Crash | Crashes Vans Vans | Vans Vans
io | 504 , 9 1.79 2 0.40 i
1980 633 10 1.58 3 0.47
1981 693 21 3.03 9 1.30
1982 637 12 1.88 4 0.63
1983 682 5 0.73 2 0.29
1984 890 19 2.13 8 0.90 |
1985 1063 18 1.68 5 0.47
1986 1173 31 2.64 9 0.77
1987 1511 29 1,92 9 0.60
ae 1729 42 2.43 15 0.87
1989 1991 39 1.97 4 0.20
1990 2072 35 1.69 12 0.58
1991 2059 40 1.94 10 0.49
| 1992 —_ 2292 46 2.01 14 0.61



Exhibit 43

Exhibit 44
Exhibit 45

Exhibit 46

Exhibit 47

Exhibit 48

Exhibit 49

Exhibit 50

Exhibit 51

Exhibit 52
Exhibit 53
Exhibit 54
Exhibit 55

Exhibit 56

Exhibit 57
Exhibit 58
Exhibit 59
Exhibit 60
Exhibit 61
Exhibit 62

Exhibit 63

95 PERCENT CONFIDENCE LIMITS FOR OBJECT STRUCK - LIGHT
TRUCKS -36-

OBJECT STRUCK - VANS -37-
95 PERCENT CONFIDENCE LIMITS FOR OBJECT STRUCK - VANS -37-

OCCURRENCE OF FIRE - CARS

OBJECT STRUCK Partitioned by AREA OF DAMAGE -38-
OCCURRENCE OF MOST HARMFUL EVENT FIRE - CARS

OBJECT STRUCK Partitioned by AREA OF DAMAGE -38-
OCCURRENCE OF FIRE - LIGHT TRUCKS

OBJECT STRUCK Partitioned by AREA OF DAMAGE -39-
OCCURRENCE OF MOST HARMFUL EVENT FIRE - LIGHT TRUCKS
OBJECT STRUCK Partitioned by AREA OF DAMAGE -39-
OCCURRENCE OF FIRE - VANS

OBJECT STRUCK Partitioned by AREA OF DAMAGE -40-
OCCURRENCE OF MOST HARMFUL EVENT FIRE - VANS

OBJECT STRUCK Partitioned by AREA OF DAMAGE -40-
ROLLOVER - CARS -41-
95 PERCENT CONFIDENCE LIMITS FOR ROLLOVER - CARS -Al-

ROLLOVERS PARTITIONED BY PRINCIPAL IMPACT POINT - CARS-42-

ROLLOVER - LIGHT TRUCKS -42-
95 PERCENT CONFIDENCE LIMITS FOR ROLLOVER

LIGHT TRUCKS -43-
ROLLOVER - VANS -43-
95 PERCENT CONFIDENCE LIMITS FOR ROLLOVER - VANS -43-
SPEED LIMIT - CARS -44-
SPEED LIMIT - CARS (CHART) -45-
SPEED LIMIT - LIGHT TRUCKS -46-
SPEED LIMIT - TRUCKS (CHART) -47-
SPEED LIMIT - VANS -48-


Exhibit 98
MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - VANS

Impact Leak Fire Leak &
Area Only Only Fire
| Front 109 29 9
Rear 88 4 4 4691
Side 47 4 4 2483
Other 68 9 | 5 | 1888
Exhibit 99

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
INJURIES INCLUDING FATALITIES - VANS

Leak Fire Leak & No Leak

Only Only Fire No Fire
1.12 0.30 0.09 98.49
1.84 0.08 0.08 97.99
1.85 0.16 0.16 97.83
3.45 0.46 0.25 95.84

Exhibit 100
95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
INJURIES INCLUDING FATALITIES - VANS

Se erp

Impact || Low % Up Low| % Up Low | Fire Up
Lim | Leak | Lim Lim | Fire | Lim Lim | Leak | Lim

0.91 | 1.12 | 1.33 0.19 | 0.30 | 0.41 0.03 | 0.09 | 0.15
1.46 | 1.84 | 2.22 0.00 | 0.08 | 0.17 0.00 | 0.08 | 0.17
1,33 | 1.85 | 2.38 0.00 | 0.16 | 0.31 0.00 | 0.16 | 0.31
4.26 0.75

-71-


calculated. The results of these calculations are in Exhibit 78. In general, if an estimated
odds ratio for a comparison model is within the 95 percent confidence level then one can
conclude that there is no measurable difference in the coefficients (although to be certain, the
complete statistical test, incorporating the standard errors of both estimates should be
computed).

None of the variables stay within the 95 percent confidence levels when the individual
vehicle types are examined. The vehicle type second-order interactions can be used to
account for the differences in the coefficients. Another approach is used here, namely a
model is built for each of the individual vehicle types. This approach, however, does not
address the remaining second order interactions. Exhibit 77, Base Model Compared to
Vehicle Specific Models, MHE Fire shows that there are many differences among cars, light
trucks, and vans. Perhaps the most important difference, due to vehicle type, is that MHE
fires in cars are very susceptible to a crash involving the rear of the car, but this is not the
case for light trucks or vans.

To examine the effect of model year of the vehicle across vehicle type note that cars, with an
odds ratio of ¥ = 0.971, are the less sensitive to the model year than light trucks with an
odds ratio of & = 0.972 but are more sensitive to model year than vans, with an odds ratio
of ¥ = 0.948. A ten-year difference in the model year of a car vs. a ten-year difference in
the model year of a van raises the likelihood of a MHE fire in a car vs. a MHE fire in a van
by {[(0.971/0.948)'° = 1.270] -1}*100 = 27.0 percent. A ten-year difference in the model
year of a truck vs. a ten-year difference in the model year of a car raises the likelihood of a
MHE fire in a truck vs. a MHE fire in a car by {[(0.972/0.971)° = 1.010] -1}*100 = 1.0
percent.

The age of the driver has different effects on the MHE fire across vehicle types. The age of
the driver odds ratio is 0.992/0.994 for cars/light trucks respectively. This suggests that the
age of the driver of a car has a slightly greater effect on the likelihood of a crash resulting in
a MHE fire. Younger drivers are more likely to have a crash resulting in a MHE fire than
older drivers, and the effect is greater with cars than with light trucks. However, there is no
real statistical difference between the two numbers. The odds ratio of driver age for vans is
1.001. This value is not statistically different from 1. Therefore one may conclude that the
age of a driver does not effect the rate of occurrence of MHE fire of vans.

The effect of the time of day, night vs. day, is not uniform across vehicle types for MHE
fire. Note that cars, with an odds ratio of Y = 1.787, are the most sensitive to the time of
day. Light trucks, with an odds ratio of ¥ = 1.659, are less sensitive and vans, with an
odds ratio of ¥ = 1,297, are the least sensitive. The relative rate of fire in a car at night
vs. a van at night is {[1.787/1.297 = 1.548] -1}*100 = 54.8 percent higher.

The speed limit has different effects on the odds ratio across vehicle types. Note that cars,
with an odds ratio of 1.038 per mph, are the least sensitive to changes of the speed limit.
Light trucks/vans, with odds ratios of 1.055/1.045 per mph respectively, are more sensitive
to changes in the speed limit. A ten mph difference in the speed limit for a truck vs. a ten
mph difference in speed limit for a car raises the relative rate of a MHE fire in a truck vs. a
MHE fire in a car by {[(1.055/1.038)'° = 1.176] - 1}*100 = 17.6 percent.

Single-vehicle crashes vs. multiple-vehicle crashes affects the rate of occurrence of MHE fire

- 66 -


Exhibit 93
MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS

Impact Leak Fire Leak & No Leak ]
Area Only Only Fire No Fire
Front 0.17 0.07 0.02 99.74
[ Rear 0.17 0.07 0.02 99,74
Side 0.40 0.06 0.02 99.52
Other 1.60 0.99 0.12 — 97.29
Exhibit 94

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS

Ir
Impact || Low % Up Low % Up Low | Fire Up
Area Lim | Leak | Lim Lim | Fire | Lim Lim | Leak | Lim
—1— aL

Front |} 0.16] 0.17 | 0.19 0.06 | 0.07 | 0.08 0.01 | 0.02 | 0.02
Rear |} 0.15 | 0.17 | 0.20 0.05 | 0.07 | 0.08 0.01 | 0.02 | 0.03
Side | 0.35] 0.40 | 0.44 0.04 | 0.06 | 0.08 0.01 | 0.02 | 0.03
Other |] 1.44] 1.60 | 1.76 0.87 | 0.99 | 1.11 0.08 | 0.12 | 0.17

All the Michigan truck data can be combined to obtain the results for all reported Michigan
truck crashes with the same caveats that one has for cars.

Exhibit 95
MICHIGAN FREQUENCY POINT OF IMPACT
ALL REPORTED CRASHES - TRUCKS

Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire
| Front 1188 349 123 329632
Rear 426 109 36 162904
Side 553 60 25 79824
L Other 963 276 45 | 36746

-75 -


Q
oh Yonsbortonon iN A N -§ Z

National Highway

Traffic
Adnministsration

DOTHS 808 208 December 1994
NHTSA Technical Report

An Analysis of Fires in Passenger Cars,
Light Trucks, and Vans

This document is avaitalbe to the public from the National Technica! Information Service, Springfield, Virginia 22161

Avail.) NTIS


Exhibit 1
Exhibit 2
Exhibit 3
Exhibit 4
Exhibit 5
Exhibit 6
Exhibit 7
Exhibit 8
Exhibit 9
Exhibit 10
Exhibit 11
Exhibit 12
Exhibit 13
Exhibit 14
Exhibit 15
Exhibit 16

Exhibit 17

Exhibit 18
Exhibit 19
Exhibit 20
Exhibit 21

Exhibit 22

List of Exhibits
YEAR OF CRASH - 1978 MODEL YEAR AND LATER CARS -5-
YEAR OF CRASH - CARS (CHART) -6-

YEAR OF CRASH - 1978 MODEL YEAR AND LATER LIGHT TRUCKS-7-

YEAR OF CRASH - TRUCKS (CHART) -8-
YEAR OF CRASH - 1978 MODEL YEAR AND LATER VANS -9-
YEAR OF CRASH - VANS (CHART) -10-
MODEL YEAR - CARS -ll-
MODEL YEAR - CARS (CHART) -12-
MODEL YEAR, AGE LIMITED TO FOUR YEARS - CARS -13-
MODEL YEAR - LIGHT TRUCKS -14-
MODEL YEAR - TRUCKS (CHART) -15-
MODEL YEAR - VANS -16-
MODEL YEAR - VANS (CHART) -17-

VEHICLE AGE in YEARS - 1978 MODEL YEAR AND LATER CARS -18-
VEHICLE AGE in YEARS - CARS (CHART) -19-
CAR PERCENT FIRE by AGE in YEARS and MODEL YEAR GROUP -20-

VEHICLE AGE in YEARS - 1978 MODEL YEAR AND LATER LIGHT
TRUCKS 24-

VEHICLE AGE in YEARS - TRUCKS (CHART) -22-
VEHICLE AGE in YEARS - 1978 MODEL YEAR AND LATER VANS -23-
VEHICLE AGE in YEARS - VANS (CHART) -24-
SINGLE-VEHICLE vs. MULTIPLE-VEHICLE CRASHES - CARS -25-

95 PERCENT CONFIDENCE LIMITS FOR SINGLE-VEHICLE vs.
MULTIPLE-VEHICLE CRASHES - CARS -25-


fatality, could have been due to fire. The sum of these additional fatalities are then added to
the minimum number of fatalities to obtain the maximum number of fatalities. The fifth
column is the total number of fatalities in 1978 or newer cars, trucks, or vans. The last row
of the exhibit contains the mean of the last three years 1990 - 1992. The mean of the last

Exhibit 71
FATALITY ESTIMATES DUE TO FIRE BY YEAR OF CRASH
Year Minimum MHE Maximum Total Car
of Number of Number of | Number of | Truck Van
Crash Fatalities Fatalities Fatalities Fatalities
1979 | 84 117 156 7049
1980 135 186 222 9985
1981 151 200 264 12004
1982 129 179 228 12072
1983 148 199 264 13447
1984 157 197 277 15793
1985 146 178 275 17866
1986 203 272 392 20230
1987 249 317 437 23086
1988 260 355 494 25532
1989 255 336 494 26514
1990 266 348 488 26553
199] 286 376 523 26894
1992 231 297 459 26264
Total 2700 3557 4973 263289
Mean 90-92 261 340 490 26570 |

three years is less susceptible to any distortion that may be due to the restriction of all
vehicle being 1978 and newer models. The results, by the year of the crash, are presented in
Exhibit 71.

Exhibit 72 displays columns 2, 3, and 4 divided by column 5 of Exhibit 71 i.e. the estimates
of minimum, MHE, and maximum number of fatalities due to fire in each year are presented
as a percent of all deaths that year, which occurred in 1978 or later model year cars, trucks
or vans. These percentages are not sensitive to the limited number of 1978 or later model

- 53 -


Exhibit 111

MICHIGAN NON-FATAL PERSONAL INJURY FIRE Crashes in TRUCKS
by IMPACT AREA

E Injury Number | Lower 95% Percent Upper 95%
Crashes Fires Limit Fire Limit
— 42314 174 0.35
17638 25 0.09
10147 21 0.12
12843 46 0.25 0.36 0.46 |
Exhibit 112

MICHIGAN PROPERTY DAMAGE ONLY FIRE Crashes in TRUCKS by IMPACT AREA

Upper 95 %
Limit

Total
Crashes

Number
Fires

287220

Lower 95%

Limit

247

0.08

135383

119

0.07

69614

58

0.06

23958

1.00

Exhibit 113

MICHIGAN FATAL FIRE Crashes in VANS by IMPACT AREA

Total Fatal Number Lower 95%
Crashes Fires Limit Fire
91 3 0.00 3.30 6.97
9 2 0.00 22.22
19 0 0.00 0.00
36 1 0.00 2.78 8.15

- 82-


Exhibit 98

MICHIGAN FREQUENCY POINT OF IMPACT

INJURIES INCLUDING FATALITIES - VANS

Impact Fire Leak & No Leak
Only Fire No Fire
29 9 9565. |
4 4 4691
4 4 2483
5 1888
Exhibit 99

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
INJURIES INCLUDING FATALITIES - VANS

Impact Leak Fire Leak & No Leak
Area Only Only Fire | No Fire
| Front 1.12 0.30 0.09 98.49
reel | 1.84 0.08 0.08 97.99
Side 1.85 0.16 0.16 97.83
Other 3.45 0.46 0.25 95.84
Exhibit 100

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
INJURIES INCLUDING FATALITIES - VANS

Impact | Low % Up Low| % | Up Low | Fire Up
Area Lim | Leak | Lim Lim | Fire | Lim Lim | Leak | Lim |
Front |} 0.91] 1.12 | 1.33 0.19 | 0.30 | 0.41 0.03 | 0.09 | 0.15
Rear | 1.46] 1.84 | 2.22 0.00 | 0.08 | 0.17 0.00 | 0.08 | 0.17
Side } 1.33] 1.85 | 2.38 0.00 | 0.16 | 0.31 0.00} 0.16 | 0.31
Other | 2.65 | 3.45 | 4.26 | 0.16 | 0.46 | 0.75 0.03 | 0.25 | 0.48

-71-



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Exhibit 13
MODEL YEAR - VANS

SO Ae

ov

fal



-

paicted

du

Exhibit 62
SPEED LIMIT - LIGHT TRUCKS

-47-


NASS Number of Vehicles Involved

Exhibit 119 shows a four-fold increase in rate of occupants with burn injuries for single-
vehicle car crashes compared to multiple-vehicle crashes but the situation is reversed for light
trucks and vans. This highlights an area for possible further investigation. Single-vehicle
crashes of light trucks and vans are less than half as likely to have occupants with burn
injuries as are multiple-vehicle crashes of light trucks and vans. Note however, that the
number of light trucks and vans with fires in the NASS database, is very small. One may
wish to compare the FARS data in Exhibits 21, 22, 23, and 24 with Exhibit 119. The FARS
data show that single-vehicle fatal crashes are more likely to have a fire or a MHE fire than

are vehicles in multiple-vehicle crashes.

Exhibit 119
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY Crash COMPLEXITY
Single-vehicle VS Multiple-vehicle Crashes

[ Cars LTV

Crash Burn Total Percent Burn Total Percent
Complexity || Injuries Injuries a Injuries Injuries __|
Single 2104 1798839 0.12 444 695203 0.06

(29) (8267) (15) (2969)

Multiple 1548 5944160 0.03 598 1115418 0.05
(26) (23331) (13) (5265)

- 89 -


fire than a car that struck a narrow object. A truck that struck a narrow object in a fatal
crash is 39.6 percent {[14.249/10.207 = 1.396] -1}*100 more likely to have a MHE fire
than a car, which struck a narrow object, which is involved in a fatal crash.

Cars, with an odds ratio of ¥ = 9.047 for striking a fixed object such as a wall, are
relatively less likely to have a MHE fire than light trucks with an odds ratio of ¥ = 9.651
but relatively more likely to have a MHE fire than vans with an odds ratio of ¥ = 6.071. A
car that struck a fixed object in a fatal crash is 49.0 percent [{(9.047/6.071) = 1.490 -
1}*100] = more likely to have a MHE fire than a van that struck a fixed object. A truck
that struck a fixed object in a fatal crash is 6.7 percent [{(9.651/9.047) = 1.067] -1}*100]
more likely to have a MHE fire than a car that struck a fixed object.

Many variables used in the model analysis are included so that the effects of these variables
can be removed and will not distort the actual findings of this investigation. The drivers age,
the time of day of the crash, and the number of vehicles involved in the crash are examples
of variables that have an effect on the probability of having a fire/MHE fire in a fatal crash.
Some variables used in the modeling cannot be accounted for in any type of compliance test.

Fuel Tank Location

The fuel tank location was partitioned into two levels; in front of the rear axle and behind the
rear axle. A model to estimate the probability of the occurrence of fire was developed using
two input variables, fuel tank location and speed limit. The data for this model was limited
to rear end crashes only and therefore the odds ratio for speed limit can not be compared to
other data in this study. The odds ratios, 95 percent confidence limits and the value of p for
the two variables are given in Exhibit 79. The model estimates that placing the tank forward
of the rear axle reduces the probability of a fire by [(1 - 0.705)*100} = 29.5 percent.

Exhibit 79
SPECIAL MODEL OF FUEL TANK LOCATION EFFECT FOR REAR IMPACT FIRES
Variable Lower 95% Odds Upper 95% P
Limit Ratio Limit Fire
Fire ¥
Forward Tank 0.537 0.705 | 0.925 | 0.0120
Speed Limit 1.007 1.021 | 1.035 0.0040

- 68 -


Exhibit 78
BASE MODEL MHE FIRE ODDS RATIO WITH
LOWER AND UPPER 95 PERCENT CONFIDENCE LIMITS

Variable | Lower 95% Odds Upper 95%
Limit Ratio ¥ Limit |
Model Year 0.960 0.970 0.812 |
Vehicle type
Truck vs. Car 1.237 1.351 1.476
Van vs. Car { 0.925 1.133 1.387
Age of driver 0.990 0.992 0.995 |
Night vs. Day 1.591 1.731 1.883
Speed limit 1.037 1.042 1.047
Multiple-vehicle 0.445 0.542 0.658
Area of damage
Rollover 0.343 0.414 0.498
Rear 1.466 1.796 2.201
Front | 0.444 0.527 0.625
|__ Side 0.325 0.393 0.477
Object struck
Vehicle 4.216 5.570 7.359
Narrow 8.981 11.28 14.169
Fixed 7.246 9.122 11.485
Overturn 1.688 2.290 3.107

of the cars only model and the cars & weight model. The reported odds ratio of 1.000017 is
the change in the odds ratio for one additional pound of weight of a car. This means that the
odds ratio increases to (1.000017)' = 1.017 if the weight of a car is increased by 1000
pounds. That is, for every additional 1000 pounds of weight, a car is 1.7 percent more
likely to have a MHE fire, if that car is involved in a fatal crash. However, the odds ratio is
very close to one and is NOT significantly different from 1 at the a = 0.1 level, ie., 10
percent confidence level.

When comparing cars, light trucks, and vans, i.¢., the second, fourth and fifth columns of
Exhibit 77, one may compare a variable (row) at a time. As a rough approximation, to
determine if the coefficients are significantly different from those of the base model, the
upper and lower 95 percent confidence limits, for the variable most harmful event fire, were

- 65 -


NASS Number of Vehicles Involved

Exhibit 119 shows a four-fold increase in rate of occupants with burn injuries for single-
vehicle car crashes compared to multiple-vehicle crashes but the situation is reversed for light
trucks and vans. This highlights an area for possible further investigation. Single-vehicle
crashes of light trucks and vans are less than half as likely to have occupants with burn
injuries as are multiple-vehicle crashes of light trucks and vans. Note however, that the
number of light trucks and vans with fires in the NASS database, is very small. One may
wish to compare the FARS data in Exhibits 21, 22, 23, and 24 with Exhibit 119. The FARS
data show that single-vehicle fatal crashes are more likely to have a fire or a MHE fire than
are vehicles in multiple-vehicle crashes.

Exhibit 119
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY Crash COMPLEXITY
Single-vehicle VS Multiple-vehicle Crashes

Cars LIv |
Crash Bum Total Percent Burn Total Percent
Complexity |} Injuries Injuries Injuries Injuries
Single 2104 1798839 0.12 444 695203 0.06
(29) (8267) (15) (2969)
Multiple 1548 5944160 0.03 598 1115418 0.05
(26) (23331) (13) (5265)

- 89 -


The exhibits for light trucks suggests that as the speed limit increases the likelihood of a
fire/MHE fire for a light truck also rises. The results appear in Exhibits 61 and 62.

SPEED LIMIT - LIGHT TRUCKS

Exhibit 61

Number Percent Number

Speed Trucks Percent
Limit in Fatal Fire Fire MHEF MHEF
MPH Crashes Trucks Trucks Trucks Trucks
15 117 | 0.85 0 0
20 237 4 1.69 3 4.27
25 2683 30 1.12 7 0.26
30 4197 54 1.29 19 0.45
i 35 7454 92 1.23 25 0.34
40 4956 72 1.45 26 0.52 |
45 9281 148 1.59 54 0.58 |
50 4803 103 2.14 30 0.62
55 47711 1618 3.39 558 1.17
[ 65 2672 106 3.97 36 1.34 |

- 46 -



NASS Object Struck

Cars striking narrow objects, such as utility poles, have the highest rate of burn injuries.

This is consistent with the FARS data in Exhibit 40.

Exhibit 121
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY OBJECT STRUCK
—>—=
Cars LTV
Object Bum Total Percent Burm Total Percent
Struck | Injuries Injuries Injuries Injuries
Vehicle | 1312 5072247 0.03 598 911980 0.07
(23) (19445) (13) (4268)
Narrow 1180 681042 0.17 196 162940 0.12
(14) (3390) (7) (808)
Fixed 499 429128 0.12 44 156176 0.03
(10) (2027) (2) (S79)
Other 0 56692 0.00 22 18734 0.12
(0) (195) @ (83)
Overturn 650 400301 0.16 182 299762 0.06
(7) (1678) (5) (1249) |

-91-


Exhibit 83
MICHIGAN FREQUENCY POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

Impact Leak Fire Leak & “|. No Leak
Area | Only Only Fire No Fire
lr Front 2715 1341 335 1573796
Rear 1559 491 129 678976
[ Side 541 261 66 383066
Other 1066 1256 114 78871

Exhibit 84
MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

Leak Fire Leak & No Leak
Only Only Fire No Fire
0.17 0.08 0.02 99.72
0.23 0.07 0.02 99.68
0.14 0.07 0.02 99.77
1.31 1.54 0.14 97.00
Exhibit 85

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

eo
. Up
i i Lim

0.02

0.02

0.02
0.17

The data of the last six exhibits can be combined to provide estimates of fires for both
personal injury and property damage only crashes. When this is done one can report on the

-71-



Exhibit 108
MICHIGAN NON-FATAL PERSONAL INJURY FIRE Crashes in CARS

by IMPACT AREA
Total Injury Number Lower 95% Percent Upper 95 %
Area Crashes Fires Limit Fire Limit
Front 362604 1162 0.30 0.32 0.34
Rear 170888 236 0.12 0.14 0.16
Side 99270 173 0.15 0.17 0.20
Other 47071 192 0.35 0.41 0.47
Exhibit 109

MICHIGAN PROPERTY DAMAGE ONLY FIRE Crashes in CARS by IMPACT AREA

Impact Total Number Lower 95% Percent Upper 95 «|
Area Crashes Fires Limit Fire Limit
Front 1578187 1676 0.10 0.11 om
Rear 681155 620 0.08 0.09 0.10
Side 383934 327 0.08 0.09 0.09
Other 81307 1370 1.60 1.98 = 1.77
Exhibit 110
MICHIGAN FATAL FIRE Crashes in TRUCKS by IMPACT AREA
Total Fatal Number Lower 95% Percent Upper 95%
Crashes Fires Limit Fire Limit
| 750 1 6.60 8.95 11.29
28 1 0.00 3.57 10.45
148 6 0.88 4.05 7.23
266 4 | 0.04 1.50 2.97

- 81 -


Exhibit 104
MICHIGAN FREQUENCY POINT OF IMPACT
ALL REPORTED CRASHES - VANS

Impact Leak Ty Fire Leak & No Leak
Area Only Only Fire No Fire
Front 225 82 25 41042
Rear 183 26 13 42186
Side 94 21 5 19190
Other 139 719 10 5867
Exhibit 105

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
ALL REPORTED CRASHES - VANS

Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire |
|
Front 0.32 0.11 0.04 99.53
Rear 0.43 0.06 0.03 99.48
Side 0.49 0.11 0.03 99.38
Other 2.28 1,30 0.16 96.26
Exhibit 106
95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
ALL REPORTED CRASHES - VANS
Impact || Low % Up Low| % Up Low Fire | Up
Area Lim | Leak | Lim Lim | Fire | Lim Lim | Leak | Lim
Front | 0.27 | 0.32 | 0.36 0.09 | 0.11 | 0.14 0.02 | 0.04 | 0.05
Rear || 0.37 | 0.43 | 0.49 0.04 | 0.06 | 0.08 0.01 | 0.03 | 0.05
Side |] 0.39 | 0.49 | 0.58 0.06 | 0.11 | 0.16 0.00 | 0.03 | 0.05
Other || 1.91 | 2.28 | 2.66 1.01 | 1.30] 1.58 0.06 | 0.16 | 0.27

-79 -



Table of Contents

List of Exhibits

Introduction

Definition of FARS Fire Occurrence and Most Harmful Event Fire

Data

Analytic Note

Year of the Crash

Model Year of the Vehicle
Number of Vehicles Involved
Weight of Cars

Area of Damage

Object Struck

Rollover

Posted Speed Limit

Salt Effect

Fatality Estimates Due to Fire
Extrication

Statistical Models

Base Models for Fire/MHE Fire
Interpretation of the Odds Ratios - Base Models
Vehicle-Specific Models

Fuel Tank Location

Michigan Data

Point of Impact

iii

-1l-

-25-

-27-

- 29 -

- 34 -

~ 40 -

-44-

- 50 -

- 52 -

- 54 -

- 56-

-57-

- 58 -

- 59 -

- 68 -

- 69 -

- 69 -


are vehicles in multiple-vehicle fatal crashes.

The variable, Area of damage, has been partitioned differently for fire and MHE fire. In
particular, the cases of rollover have been absorbed in the control set of cases for the output
variable fire, but not for the output variables MHE fire. To interpret the results, all values of
odds ratio, ¥, are divided by the odds ratio for being struck in the side to obtain ¥. For
fire, the values of ¥’ are Rear (2. 157/0.832 = 2.593) and Front (1.073/0.832 = 1.290).

For MHE fire, the new values of ¥' are Rear (1 .796/0.394 = 4.558), Front (0.527/0.394 =
1.338) and Rollover (0.414/0.394 = 1.051).

The interpretation for vehicles involved in fatal crashes follows. Vehicles struck in the rear
are 159.3 percent/355.8 percent more likely to have a fire/MHE fire than a vehicle struck in
the side. Vehicles struck in the front are 29.0 percent/33.8 percent more likely to have a
fire/MHE fire than a vehicle struck in the side. There are far more crashes where the
damage to the vehicle occurs in the front rather than the rear. Consequently, there are more
fires/MHE fires in crashes where the damage to the vehicle occurs in the front rather than
the rear (see the Area of Damage exhibits for cars, light trucks and vans, exhibits 30 through
39). Vehicles that rolled over are 5.1 percent more likely to have an MHE fire than a
vehicle struck in the side.

Object struck is treated in a similar way. In this case, the odds ratios, ¥, for Vehicle,
Narrow and Fixed are divided by the odds ratio for overtum. The rescaled odds ratios, ¥’,
for fire are Vehicle (4.541/1.780 = 2.551), Narrow (7.931/1.780 = 4.456), and Fixed
(6.217/1.780 = 3.493). The rescaled odds ratios, ¥', for MHE fire are Vehicle
(5.570/2.290 = 2.432), Narrow (11.280/2.290 = 4.926), and Fixed (9.122/2.290 = 3.983).

Vehicles that struck another vehicle in a fatal crash are 155.1 percent/143.2 percent more
likely to have a fire/MHE fire than are overturned vehicles. Vehicles that struck a narrow
object, such as a pole, are 345.6 percent/392.6 percent more likely to have a fire/MHE fire
than overturned vehicles. Vehicles that struck a fixed object, such as a wall, are 249.3
percent/ 298.3 percent more likely to have a fire/MHE fire than are overturned vehicles.

Vehicle-Specific Models
In addition to the base model, Exhibit 74, models for the variable fire, for each vehicle type

(cars, light trucks and vans) were estimated. The sets of odds ratios for each model are in
Exhibit 75.

- §9 -


to the front (Exhibit 75 and 77). Over the time period of the study, 1979 through 1992,
there were 3275/839 cases of fatal crashes where a car was struck in the front and had a
fire/MHE fire. During this period there were 640/270 cases where a car was struck in the
rear and had a fire/MHE fire (Exhibit 30). The data suggest that crash tests of cars should
include frontal crash tests to address the largest number of postcollision fires, and rear
crashes, to address the greatest likelihood of postcollision fires, as part of the testing
procedure.

The object that is struck by a vehicle involved in a fatal crash affects the likelihood of a
fire/MHE fire. Vehicles striking narrow objects, such as telephone poles, are more likely to
have a fire/MHE fire than vehicles striking other types of objects. In particular, a vehicle
striking a narrow object is 27.6 percent and 23.7 percent more likely to have a fire/MHE
fire, respectively, than vehicles that strike other fixed objects (Exhibit 74). However, there
are relatively few cases of a vehicle being struck in the rear by a narrow object, (see
Exhibits 46-51), i.e., both types of events occur, but usually not together.

The Michigan data show that car crashes involving injuries have a significantly higher rate of
fire than do crashes that only have property damage if the damage is to the front rear or side.
However, the situation is reversed for the "other" impact areas, which includes damage to
the under carriage (Exhibits 81 and 84).

Light truck in crashes with personal injury have a higher rate of fire with front impacts than
with side impacts (Exhibit 90).

The Michigan data was used to calculate the conditional probability of a fire given a fuel leak
to be 0.075 or 7.5 percent. However, fire was 52.8 times as likely if a fuel leak was
reported as opposed to when a fuel leak was not reported (Exhibit 116).

Most burn injuries, due to vehicle fires, occur in crashes with Delta V in excess of 20 mph
(Exhibit 122).

Virtually all fires that originate in the fuel system, rather than the engine compartment, are
major fires. If the origin of the fire is not the fuel system, this usually means the fire
originated in the engine compartment, then less than half of the fires are classified as major
fires (Exhibit 125).

- 97 -


NASS Entrapment

Entrapment has a fundamentally different type of relationship with fire than do the previous
NASS variables which have been examined so far. The previous variables are expected to
have a "causal" relation with fire. That is a change in the crash complexity or Delta V is
expected to change the rate of vehicle fires. However, although entrapment like extrication,
see Exhibit 73, does not cause fires and fires do not cause entrapment, the two variables
may be associated.

To examine entrapment the NASS partition of minor and major fire are used. NASS
classifies a fire as a major fire if the fire involved the whole passenger compartment or
several different compartments such as the engine compartment, trunk compartment or
undercarriage.

The rate of individuals that are entrapped in major fires is 1.95 percent, the lowest of the
three groups. The rate of entrapment for minor fires, 21.35 percent, is almost eleven times
greater than the rate for major fires. The results are found in Exhibit 124.

Exhibit 124
ENTRAPMENT
Fire Entrapped Not Percent
Level Entrapped Entrapped
No Fire 24465 3973770 6.12
(355) (16045)
Minor Fire 1222 4502 21.35
© (41)
Major Fire 131 6599 1.95
| @) 0)

S. C. Partyka, in her July 1992 paper "Fires and Bums in Towed Light Passenger Vehicle
Crashes" Office of Vehicle Safety Standards points out that NASS also provides information
on the lack of operable doors near the occupant’s seat position which can also contribute to
bum injuries. Interested readers are referred to her paper.

- 94 -


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SPEED LIMIT - CARS
- 45 -

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Exhibit 44
OBJECT STRUCK - VANS

——]
Object Vans Number Percent Number Percent |
Struck in Fatal Fire Fire MHEF MHEF
Crashes Vans Vans
Vehicle 11113 219 1.97 48 0.43
Narrow 793 49 6.18 25 3.15
Fixed 1354 57 4.21 23 1.70
Other 3580 19 0.53 7 0.20
Overtum 1077 12 1.11 3 0.28
Exhibit 45

95 PERCENT CONFIDENCE LIMITS FOR OBJECT STRUCK - VANS

Object Lower Percent Upper Lower | Percent une |
Struck Limit Fire Limit Limit MHEF Limit
Vehicle L 1.71 1.97 2.24 0.30 0.43 0.55
Narrow 4.50 6.18 7.87 1.91 3.15 4.38
Fixed 3.13 4.21 §.29 1.03 1.73 2.43
Other 0.29 0.53 0.78 0.05 0.20 0.35
Overturn 0.47 1.11 1,74 0.00 0.28 0.60 |

The preceding data can be partitioned by both Object Struck and Area of Damage. By
definition the object struck is the first object struck or an overtum. Thus, virtually all coded
overturns are also coded as rollovers, but all rollovers that occur after a vehicle has struck an
object are not necessarily coded as overturns. Note that the greatest number of occurrences
of fires are vehicle-to-vehicle crashes with damage to the front, rear and side. However, in
the case of a rollover, a vehicle is most likely to strike a fixed object. In this case the
number of occurrences by damaged area is highly dependent on the object struck. That is,
there is a statistical interaction between object struck and area of damage. The results of this
partition appear in Exhibits 46 through 51.

-37-


US. Department
of Transportation

National Highway
Tratfic Safety
Administration

400 Seventh St, S.W.
Washington, D.C. 20590

Oficial Business
Penalty lor Private Use $300

@ises.



Exhibit 76
BASE MODEL FIRE ODDS RATIO WITH
LOWER AND UPPER 95 PERCENT CONFIDENCE LIMITS’

Variable Lower 95% Odds
Limit

Ratio ¥

Vehicle age | 1.019
Vehicle type |

Truck vs. Car | 1.021 1.075 1.132
Van vs. Car 0.321 0.975 2.962
Age of driver 0.990 0.991 0.993
Night vs. Day 1.464 1.531 1,602

Speed limit - 1.033 1.035 1.038
Multiple-vehicle 0.723 0.807 0.902
Area of damage
Rear 1.968 2.157 2.364

Front 1.015 1.073 1,134
Side

Object struck

Vehicle

When comparing cars, light trucks, and vans, i.e., the second, fourth and fifth columns of
Exhibit 75, one may compare a variable (row) at a time. As a rough approximation, to
determine if the coefficients are significantly different from those of the base model, the
upper and lower 95 percent confidence limits, for the variable fire, were calculated. The
results of these calculations are in Exhibit 76.

In general, if an estimated odds ratio for a comparison model is within the 95 percent
confidence level then one can conclude that there is no measurable difference in the
coefficients (although to be certain, the complete statistical test, incorporating the standard

oe

2 Wosmer, David W. and Lemeshow, Stanley, Applied Logistic Regression, New York:
John Wiley & Sons, Inc., 1989, Chapter 3p. 44.

-61-


Exhibit 66
95 PERCENT CONFIDENCE LIMITS FOR SALT EFFECT - CARS

| Salt | Lower Percent | ve Lower | Percent vine |
Status Limit Fire Limit Limit MHEF Limit

Salt Belt 2.48 2.57 | 2.67 0.42 0.46 0.50 |
Sun Belt 1.92 2.02 2.12 0.72 0.78 0.84
Other [ 2.40 2.50 | 2.59 0.77 0.83 0.89

Light trucks registered in a salt belt state have approximately a 10 percent higher rate of
occurrence of fires than do light trucks in the sun belt states. However, light trucks
registered in the salt belt states are approximately 50 percent less likely to have a fire
identified as the MHE than a truck registered in a sun belt state. A total of 558 light trucks
from the salt belt states experienced a fire. There were 746 crashes involving a truck from
the sun belt states that had a fire. There were 111 light trucks from the salt belt states,
which were identified as having a fire as the MHE. A total of 330 light trucks from sun belt
states were identified as having a fire as the MHE. The details are in Exhibits 67 and 68.

Exhibit 67
SALT EFFECT - LIGHT TRUCKS

Salt Trucks Number Percent Number Percent
Status in Fatal Fire Fire MHEF MHEF
Crashes Trucks Trucks Trucks Trucks
j Salt Belt 19945 558 2.80 11 0.56
Sun Belt 30300 746 2.46 330 1.09
| Other 34793 914 2.63 308 0.89
Exhibit 68

95 PERCENT CONFIDENCE LIMITS FOR SALT EFFECT - LIGHT TRUCKS

Salt Lower Percent Upper Lower Percent Upper
Status Limit Fire | Limit Limit MHEF Limit
Salt Belt 2.57 2.80 3.03 0.45 0.56 0.66
Sun Belt 2.29 2.46 2.64 0.97 1.09 1.21
Other 2.46 2.63 2.80 i 0.79 | 0.89 0.98

Vans registered in salt belt states have approximately a 5 percent higher rate of occurrence of

-51-


Michigan Data

Michigan collects data on fuel leaks and fires as part of their police accident reporting
system. These data are collected for any injury, including fatalities, and property damage
crashes. Michigan has partitioned the exposure data into four disjoint categories, namely:
(1) fuel leak but no fire, (2) fire but no fuel leak, (3) fuel leak and fire, and (4) no fuel leak
and no fire. The Michigan area of impact, (similar to the area of damage) was partitioned
into four disjoint categories: front, rear, side and other. Data were examined for the years
1982 to 1991 for 1978 and newer model year vehicles. In addition to the different time
frame over which the Michigan data were collected, there are two other distinct differences
between the Michigan data and the FARS data used in the previous sections of this report.
First the Michigan police crashes reports, on which this part of the analysis is based, collects
information on fuel leaks. Second the Michigan data contains information on all crashes for
which a police accident report was filed and is not limited to fatal crashes as is FARS.

The FARS data produce rates of fire and MHE fire considerably higher (about double) for
cars with damage to the rear than to the front of the car. However, the Michigan data for
both injuries including fatalities (Exhibits 80, 81, and 82) and property damage only crashes
for cars (Exhibits 83, 84, and 85) do not support this finding. In fact the rate of occurrence
of fire but no leak for crashes involving personal injury including death, is 0.28 percent
when the impact area is the front compared to 0.10 for impact area to the rear. This
difference may be due to the fact that a much larger percentage of less serious, i.e. not fatal,
crashes are included. See the exhibit of Michigan fatalities within cars later in this section,
Exhibit 101.

Vehicles in crashes resulting an injury; incapacitating, non-incapacitating or possible, are
more likely to have a fire, with or without a leak, than a crash where only property is
damaged, see Exhibit 81 and 84. That is, more serious crashes are more likely to have a
fire than less serious crashes.

Point of Impact
Exhibit 80

MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - CARS

| Impact Leak Fire Leak & No Leak

Area Only Only Fire No Fire
Front 3687 1033 286 360749 |

Rear 1966 163 98 168952

Side 1170 170 72 99982

Other |} 1317 153 56 46208

- 69 -


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Exhibit 64
SPEED LIMIT - VANS

~ 49 -


NASS Data

The National Highway Traffic Safety Administration collects national traffic crash data to
evaluate highway and vehicle safety standards. The National Accident Sampling System
(NASS) Crashworthiness Data System (CDS) consists of twenty-four teams of crash
researchers throughout the country. Each site samples the set of police accident reports
involving passenger cars, light trucks and vans which were towed from the scene of the
crash. The crashes investigated in CDS are a probability sample of all police reported
crashes in the U.S. Each crash that occurs within a CDS team’s area has a chance of being
included in the sample. The chosen design makes it possible to compute national estimates.
In particular, NASS estimates are available for bum injuries that were the result of a vehicle
fire from 1988-1993. The bum injury data is obtained from detailed medical records of the
injured occupants. The counts reported in this section are estimates of individuals who
received an injury and in particular a burn injury.

Fires are rare events and occur in less than one percent of all crashes where a vehicle is
towed from the scene of the crash. The total number of crashes sampled by the twenty four
teams is relatively small, about 5000 per year. As a result, there are very few vehicles in
the NASS database that had a fire, most likely less than 50 per year. The number of
vehicles in the NASS database is so small that national estimates of burn injuries should be
interpreted with care. Note, for example, in Exhibit 118 NASS estimates that no one year
old vehicle had a fire that caused a burn injury. This does not mean that one year old
vehicles do not have fires that cause bum injuries, but rather that there were no vehicles of
this age that had a fire with bum injuries in the database. Although, due to the scarcity of
the data, one cannot make precise estimates of burn injuries within vehicles that have a fire,
the estimates can suggest relationships among the variables. For this reason the partitions of
the data are rather coarse. This limitation of NASS data is for fires and other relatively rare
events only and does not necessarily apply to other types of investigations. An underlying
assumption of the burn injury data is that the burn resulted from a vehicle fire. As additional
data are collected over the years and added to the database, this difficulty may be
ameliorated. Confidence intervals and charts are not included for NASS estimates for this
reason. The lower numbers in parenthesis are the unweighted number of observations on
which the estimates are based.

NASS Vehicle Age

The data of Exhibit 118 does not suggest a relationship between vehicle age and occupants
that had a burn injury and occupants that had any injury within vehicles.

-87-


Model Year of the Vehicle

The number of vehicles involved in fatal crashes, the number of fire occurrences, the number
of MHE fires, the raw percentage rate of occurrence of fire and MHE fire for cars, light
trucks and vans, by model year of the vehicle under analysis, appears below. The rate of
fire by model year does not seem to exhibit a trend for cars. The rate of MHE fire shows an
increase for older model years, increasing from a rate of 0.50 percent for model year 1990 to
0.88 percent for model year 1978. 1992 model year cars have the highest rate of MHE fire
with a rate of 1.23 percent. However, only 1495 of the 1992 model year cars were involved
in a fatal crash. The car statistical model for MHE fires shows that there is a small increase
in the rate of MHE fire as the model year decreases. During the time frame of this study,
front wheel drive and fuel injection have become popular options and fuel tanks have been
placed in different locations of the vehicle. It is possible that better designs of the later
model vehicles may contribute to a reduction of the fire rate, if so, it may be detected when
model year is examined. The results for cars are in Exhibits 7 and 8.

Exhibit 7
MODEL YEAR - CARS

Model Cars Number Percent Number Percent
Year in Fatal Fire Fire MHEF MHEF
Crashes Cars Cars Cars Cars
1978 36180 947 2.62 319 0.88
1979 37310 1028 2.76 324 0.87
1980 29834 701 2.35 177 0.59
1981 | 25174 549 2.18 172 0.68
1982 20968 498 2.38 137 0.65
1983 19335 465 2.40 125 0.65 |
1984 23855 595 2.49 150 0.63 |
1985 21233 524 2.47 119 0.56
1986 19167 469 2.45 130 0.68
1987 16057 370 2.30 118 0.70 1
1988 13431 265 1.97 68 0.51 |
1989 al 9689 187 1.93 51 0.53
1990 5972 132 2.21 30 0.50
1991 3665 16 2.03 21 0.56
1992 1495 48 3.11 19 1,23
A. C. Malliaris, in his August 1990 paper, "Impact-Induced Car Fires-A Comprehensive

Investigation", [Accident Analysis and Prevention, Vol. 23, Issue #4, pp 257-273] suggests

-li-


Exhibit 81

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
INJURIES INCLUDING FATALITIES - CARS

Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire
= 1.01 0.28 0.08 98.63
Rear 1.15 0.10 0.06 98.70
Side 1.15 0.17 0.07 98.61
Other ' 2.76 0.32 0.12 96.80_|

The column headings for Exhibits 82, 85, 88, 91, 94, 97, and 100 mean the following:
“Low Lim" and "Up Lim" refer to the lower and upper 95 percent confidence limits for the
variable between. "% Leak" refers to the percentage of crash-involved vehicles that had a
fuel leak but no fire. "% Fire" refers to the percentage of vehicles that had a fire but no
fuel leak. "Fire Leak" refers to the percentage of vehicles that had both a fire and a fuel

leak.
Exhibit 82
95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
INJURIES INCLUDING FATALITIES - CARS

Impact Lo % Up Low] % Up Low | Fire up |

Area Lim | Leak | Lim Lim | Fire | Lim Lim | Leak | Lim
aos {Lim

Front | 0.98) 1.01 | 1.04 0.27 } 0.28 | 0.30 0.07 | 0.08] 0.09

Rear |} 1.10] 1.15 | 1.20 0.08 | 0.10 | 0.11 0.05 | 0.06 | 0.07
| Side } 1.09] 1.15 | 1.22 0.14 | 0.17 | 0.19 0.05 | 0.07] 0.09
| Other |] 2.61 | 2.76 | 2.91 0.27 | 0.32 | 0.37 0.09 | 0.12 | 0.15

- 70 -


Exhibit 96
MICHIGAN PERCENTAGE RATE POINT OF IMPACT
ALL REPORTED CRASHES - TRUCKS

Impact | Leak Fire Leak & No Leak
Area Only Only Fire No Fire
Front 0.36 0.11 0.04 99.50
Rear 0.28 0.07 0.02 99.63
Side 0.69 0.07 0.03 99.21
Other 2.53 0.73 0.12 96.62_|

Exhibit 97
95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
ALL REPORTED CRASHES - TRUCKS

Impact | Low % “Tup|) low] % Up Low | Fire
Area Lim | Leak | Lim Lim | Fire | Lim Lim | Leak
Front | 0.34 | 0.36 | 0.38 0.09 | 0.11 | 0.12 0.03 | 0.04
Rear || 0.25 | 0.28 { 0.30 0.06 | 0.07 | 0.08 0.02 | 0.02
Side || 0.63 | 0.69 | 0.74 0.06 | 0.07 | 0.09 0.02 | 0.03
Other | 2.37} 2.53 | 2.69 0.64 | 0.73 | 0.81 0.08 | 0.12

The number of van fires in Michigan is small and many of the 95 PERCENT confidence
intervals are so large that they include the estimates of other impact areas. This suggests that
more data are needed to estimate the effects of impact area on fires in vans in the State of
Michigan. These preliminary Michigan data are somewhat contrary to the findings of the
FARS van data in section I of this study.

- 16 -


Area of damage: The principal impact point of damage to the vehicle under analysis. The
data were partitioned into five categories.

Rollover: The vehicle rolled at least one quarter of a full turn.

Front: The vehicle does not rollover and has principal damage to the front of the
vehicle, i.e., clock positions 11, 12, or 1.

Rear: The vehicle does not rollover and has principal damage to the rear of the
vehicle, i.e., clock positions 5, 6 or 7.

Side: The vehicle does not rollover and has principal damage to the side of the
vehicle, i.e., clock positions 2, 3, 4, 8, 9, or 10.

Other: The vehicle does not rollover and has principal damage to an area other than
the front, rear, or side, for example, the undercarriage or roof.

Rollover: The vehicle rolled at least one quarter of a full tum. The difference between this
variable and the preceding variable is that the front, rear, side and other were collapsed into
the single response of nonrollover.

Weight: This variable applies only to cars. The curb weight of the vehicle measured in
pounds.

Salt effect: This variable partitions the states into the “salt belt" states that use salt and other
corrosive material on roadways which affect vehicle corrosion, the "sun belt" states and other
states. The states of Connecticut, Ulinois, Indiana, Maine, Massachusetts, Michigan,
Minnesota, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island,
Vermont, West Virginia, and Wisconsin are considered the “salt belt" states. The “sun belt"
states are defined to be Alabama, Arizona, Florida, Georgia, Hawaii, Louisiana, Mississippi,
New Mexico, South Carolina, and Texas. All other states and the District of Columbia are
considered other states.

Speed limit: The posted speed limit in mph.

Object struck: The kinematics of a crash are dependent on the type of object struck by the
vehicle under analysis. The objects were partitioned into five mutually exclusive sets using
the FARS definitions of first harmful event. Note that object struck is the first object struck
or an overturn, if that occurred first.

Vehicle: If the vehicle struck a motor vehicle of any kind.

Narrow: A narrow stationary. Narrow objects include: highway/traffic sign posts,
overhead sign supports, luminary/light supports, utility poles, fire hydrants and trees.

Fixed: Large blunt objects. Fixed objects include: boulders, buildings, impact
attenuators/crash cushions, bridge piers or abutments, bridge parapet ends, guardrails,
concrete traffic barriers, longitudinal] barriers, culverts, curbs, ditches, embankments,
fences, and walls.


Exhibit 90

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
INJURIES INCLUDING FATALITIES - LIGHT TRUCKS

J Impact | Leak Fire Leak & Ty No Leak
Area Only Only Fire No Fire
Front 1.59 0.36 0.15 97.90
Rear 1,07 0.11 0.04 98.78
Side 2.60 0.16 0.09 97.14
L_ Other 4.19 0.26 0.11 95.44
Exhibit 91

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
INJURIES INCLUDING FATALITIES - LIGHT TRUCKS

—
Impact Low % Up Low| % Up Low | Leak Up
Area Lim Leak | Lim Lim | Fire | Lim Lim | Fire | Lim
Front 1.47] 1.59 | 1.71 0.31 | 0.36 | 0.42 0.11] 0.15 | 0.19
Rear 0.92 | 1.07] 1.22 0.06 | 0.11 | 0.15 0.01 | 0.04] 0.07
Side 2.3 | 2.60 | 2.91 0.08 | 0.16 | 0.24 0.04 | 0.09 | 0.15
Other | 3.86 | 4.19 | 4.53 0.17 | 0.26 | 0.34 0.05 | 0.11 | 0.17
Exhibit 92
MICHIGAN FREQUENCY POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS
Impact Leak Fire Leak & No Leak
Area Only Only Fire No Fire
Front 496 190 57 286973
Rear 235 90 29 135264
Side 278 43 15 69556
Other 389 241 30 23687 ‘|

- 74 -


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Exhibit 117

MICHIGAN FIRE RATE BY VEHICLE AGE


fatality, could have been due to fire. The sum of these additional fatalities are then added to
the minimum number of fatalities to obtain the maximum number of fatalities. The fifth
column is the total number of fatalities in 1978 or newer cars, trucks, or vans. The last row
of the exhibit contains the mean of the last three years 1990 - 1992. The mean of the last

Exhibit 71
FATALITY ESTIMATES DUE TO FIRE BY YEAR OF CRASH

Year Minimum MHE Maximum Total Car
of Number of Number of | Number of | Truck Van
Crash Fatalities Fatalities Fatalities | Fatalities
1i7 156 7049

186 222 9985

200 264 12004

179 228 12072

1983 148 199 264 13447
1984 157 197 271 15793
1985 | 146 178 275 17866
1986 203 272 392 20230
1987 249 317 437 23086
1988 260 355 494 25532
1989 255 336 494 26514
1990 266 348 488 26553
1991 286 376 523 26894
1992 231 297 | 459 26264
Total 2700 3557 4973 263289
Mean 90-92 261 340 490 | 26570

three years is less susceptible to any distortion that may be due to the restriction of all
vehicle being 1978 and newer models. The results, by the year of the crash, are presented in
Exhibit 71.

Exhibit 72 displays columns 2, 3, and 4 divided by column 5 of Exhibit 71 i.e. the estimates
of minimum, MHE, and maximum number of fatalities due to fire in each year are presented
as a percent of all deaths that year, which occurred in 1978 or later model year cars, trucks
or vans. These percentages are not sensitive to the limited number of 1978 or tater model

- 53 -


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Exhibit 64

SPEED LIMIT - VANS

- 49 -


Exhibit 29
95 PERCENT CONFIDENCE LIMITS FOR WEIGHT CLASS - CARS

Weight Lower Percent Upper Lower Percent
Class Limit Fire Limit Limit MHEF
Class 1 1.66 1.84 2.03 0.49 0.60
Class 2 2.05 2.16 2.27 0.55 0.61
Class 3 2.26 2.38 2.50 0.55 0.61
Class 4 2.70 2.82 2.95 0.73 0.79 0.86 |
Class 5 2.36 2.54 2.71 0.68 0.78 0.88
Class 6 2.30 2.47 2.65 0.69 0.79 0.89

Area of Damage

The area where the damage to the vehicle occurred was partitioned into five mutually
exclusive ranges: rollover, front, rear, side, and other. If the vehicle experienced a
rollover, despite what other damage occurred, the vehicle was coded as a rollover.

Over half the cars involved in fatal crashes received damage to the front of the vehicle and
there were more fire/MHE fires reported for cars with damage in the front than any other
area. However, the rate of fire occurrence, i.e., the percentage fire/MHE fire, for cars with
damage to the front, is the second lowest for both fire and MHE fire. Relatively few cars in
fatal crashes have damage to the rear of the vehicle. But when the rear of a car is involved,
one experiences the highest rate of occurrence of both fire/MHE fire. It is important to
compare this exhibit with the corresponding exhibits for light tricks and vans. Note that cars
are more likely to have a fire/MHE fire if the rear is involved compared to light trucks or
vans, i.e., cars are more susceptible to fire when the rear is involved than are light trucks
and vans. This may be due to the location of the fuel tank, especially vs. pickup trucks,
wherein the fuel tanks are generally located below the cab and the bed, often between the
frame rails. The rates of occurrence of fire/MHE fire for cars experiencing damage to the
rear are 5.38 percent/2.27 percent, respectively. These are the highest rates for any area of
damage. Most cars experience damage to the front of the vehicle, and these frontally
damaged vehicles experience the greatest number of fires (3275)/MHE fires (839), with rates
of occurrence of 2.13 percent/0.55 percent, respectively, see Exhibits 30 and 31.

-29 -


NASS Data

The National Highway Traffic Safety Administration collects national traffic crash data to
evaluate highway and vehicle safety standards. The National Accident Sampling System
(NASS) Crashworthiness Data System (CDS) consists of twenty-four teams of crash
researchers throughout the country. Each site samples the set of police accident reports
involving passenger cars, light trucks and vans which were towed from the scene of the
crash. The crashes investigated in CDS are a probability sample of all police reported
crashes in the U.S. Each crash that occurs within a CDS team’s area has a chance of being
included in the sample. The chosen design makes it possible to compute national estimates.
In particular, NASS estimates are available for burn injuries that were the result of a vehicle
fire from 1988-1993. The bum injury data is obtained from detailed medical records of the
injured occupants. The counts reported in this section are estimates of individuals who
received an injury and in particular a burn injury.

Fires are rare events and occur in less than one percent of all crashes where a vehicle is
towed from the scene of the crash. The total number of crashes sampled by the twenty four
teams is relatively small, about 5000 per year. As a result, there are very few vehicles in
the NASS database that had a fire, most likely less than 50 per year. The number of
vehicles in the NASS database is so small that national estimates of burn injuries should be
interpreted with care. Note, for example, in Exhibit 118 NASS estimates that no one year
old vehicle had a fire that caused a bum injury. This does not mean that one year old
vehicles do not have fires that cause bum injuries, but rather that there were no vehicles of
this age that had a fire with burn injuries in the database. Although, due to the scarcity of
the data, one cannot make precise estimates of burn injuries within vehicles that have a fire,
the estimates can suggest relationships among the variables. For this reason the partitions of
the data are rather coarse. This limitation of NASS data is for fires and other relatively rare
events only and does not necessarily apply to other types of investigations. An underlying
assumption of the burn injury data is that the bum resulted from a vehicle fire. As additional
data are collected over the years and added to the database, this difficulty may be
ameliorated. Confidence intervals and charts are not included for NASS estimates for this
reason. The lower numbers in parenthesis are the unweighted number of observations on
which the estimates are based.

NASS Vehicle Age

The data of Exhibit 118 does not suggest a relationship between vehicle age and occupants
that had a burn injury and occupants that had any injury within vehicles.

- 87 -


NASS Fire Origin

The origin of the fire is partitioned into three levels; fuel system, engine compartment and
other. In this context, the fuel system consists of the fuel tank(s), fuel supply and vent lines
and the filler neck. The engine area denotes the open or closed area which houses the
engine. For an engine area fire, the cause for the fire is inconsequential, it may be electrical
or fuel related. The fire’s relative location to the engine is the important consideration.

Note that virtually all of the fuel system fires, 1908 out of 1927 or 99.01 percent, are major
fires. If the origin of the fire is not the fuel system, then less than half of the fires are major

fires. The results are in Exhibit 125.

Exhibit 125
ORIGIN of FIRES
Fire Fuel Percent Engine | Percent | Other | Percent
Level System Fuel Area Engine Other
System Area

19 0.33 4613 80.59 1092 19.07

Q) (36) 9)
1908 28.35 4342 64.53 479 712

(25) (60) (9)

- 95 -


Exhibit 88

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
ALL REPORTED CRASHES - CARS

| Impact || Low %| Up Low % | Up Low | Fire Up
Area ]} Lim | Leak | Lim Lim | Fire | Lim Lim | Leak Lim
Front | 0.32 | 0.33 | 0.34 0.12 | 0.12 | 0.13 0.03 | 0.03 0.03
Rear || 0.40} 0.41 | 0.43 0.07 | 0.08 | 0.08 0.02 | 0.03 0.03
Side | 0.34 | 0.35 | 0.37 0.08 | 0.09 | 0.10 0.02 | 0.03 0.03
Other } 1.77] 1.85 | 1.92 1.04 | 1.09 | 1.15 O11 | 0.13 0.15

Crash-involved light trucks involving personal injury, with damage to the rear, have fewer
fires and a lower rate of fire than any other impact area (Exhibits 89 and 90). This is
consistent with the FARS data, Exhibit 36.

Exhibit 89

MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - LIGHT TRUCKS

Ea Leak Fire Leak & No Leak
Area Only Only Fire No Fire
Front 692 159 66 42659
Rear 191 19 7 17640
Side 275 17 10 10268
| Other | 547 | 35 15 13059

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Exhibit 15
VEHICLE AGE in YEARS - CARS

-19-



The exhibits for vans suggests that as the speed limit increases the likelihood of a fire/MHE
fire for a van also rises. Exhibits 63 and 64 contain the results.

Exhibit 63
SPEED LIMIT - VANS

Number
Fire
Vans

Percent
Fire
Vans

Number
MHEF
Vans

Percent
MHEF
Vans

0.00

0.00

0.12

0.24

0.43

0.49

0.61

0.29

0.77

1.21

- 48 -



Exhibit 83

Exhibit 84

Exhibit 85

Exhibit 86

Exhibit 87

Exhibit 88

Exhibit 89

Exhibit 90

Exhibit 91

Exhibit 92

Exhibit 93

Exhibit 94

Exhibit 95

Exhibit 96

Exhibit 97

Exhibit 98

MICHIGAN FREQUENCY POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - CARS

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE by
POINT OF IMPACT PROPERTY DAMAGE ONLY - CARS

MICHIGAN FREQUENCY POINT OF IMPACT ALL REPORTED
CRASHES - CARS

-T1-

-11-

-11-

-72-

MICHIGAN PERCENTAGE RATE POINT OF IMPACT ALL REPORTED

CRASHES - CARS

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE by
POINT OF IMPACT ALL REPORTED CRASHES - CARS

MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - LIGHT TRUCKS

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
INJURIES INCLUDING FATALITIES - LIGHT TRUCKS

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE by
POINT OF IMPACT INJURIES INCLUDING FATALITIES - LIGHT
TRUCKS

MICHIGAN FREQUENCY POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE by
POINT OF IMPACT PROPERTY DAMAGE ONLY - LIGHT TRUCKS

MICHIGAN FREQUENCY POINT OF IMPACT
ALL REPORTED CRASHES - LIGHT TRUCKS

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
ALL REPORTED CRASHES - LIGHT TRUCKS

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE by
POINT OF IMPACT ALL REPORTED CRASHES - LIGHT TRUCKS

MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - VANS

ix

-72-

-73-

-73-

-74-

-74-

-74-

-15-

-75-

-75-

-16-

-16-

-TI-


Exhibit 78
BASE MODEL MHE FIRE ODDS RATIO WITH
LOWER AND UPPER 95 PERCENT CONFIDENCE LIMITS

Variable Lower 95% Odds Upper 95% ]
Limit Ratio ¥ Limit
Model Year | 0.960 0.970 0.812
Vehicle type
Truck vs. =m 1.237 1.351 1.476
[ Van vs. Car 0.925 1.133 1.387
Age of driver 0.990 0.992 0.995
Night vs. Day 1,591 1.731 1.883
Speed limit 1.037 1.042 1.047
Multiple-vehicle 0.445 0.542 0.658 |
Area of damage
Rollover 0.343 0.414 0.498
Rear 1.466 1.796 2.201
Front 0.444 0.527 0.625
Side 0.325 0.393 0.477
Object struck
| Vehicle 4.216 5.570 7.359 |
Narrow 8.981 11.28 14.169
Fixed 7.246 9.122 11.485

Le Overtum 1.688 2.290 3.107 |

of the cars only model and the cars & weight model. The reported odds ratio of 1.000017 is
the change in the odds ratio for one additional pound of weight of a car. This means that the
odds ratio increases to (1.000017)'TM = 1.017 if the weight of a car is increased by 1000
pounds. That is, for every additional 1000 pounds of weight, a car is 1.7 percent more
likely to have a MHE fire, if that car is involved in a fatal crash. However, the odds ratio is
very close to one and is NOT significantly different from 1 at the « = 0.1 level, i-e., 10
percent confidence level.

When comparing cars, light trucks, and vans, i.e., the second, fourth and fifth columns of
Exhibit 77, one may compare a variable (row) at a time. As a rough approximation, to
determine if the coefficients are significantly different from those of the base model, the
upper and lower 95 percent confidence limits, for the variable most harmful event fire, were

- 65 -


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Exhibit 62

SPEED LIMIT - LIGHT TRUCKS

-47-



damage to the rear. A car with damage to the rear in a fatal crash is {[2.484/0.842 =
3.950] -1}*100 = 395.0 percent more likely to have a fire than a van with damage to the
rear in a fatal crash.

Cars, with an odds ratio of ¥ = 1.043, for damage to the front, are less sensitive than light
trucks ¥ = 1.175, and vans ¥ = 1.165 for damage to the front. A van receiving frontal
damage in a fatal crash is {[1.165/1.043 = 0.895] -1}*100 = 11.7 percent more likely to
have a fire than a frontally damaged car. A frontally damaged truck in a fatal crash is
{[1.175/1.043 = 1.127] -1}*100 = 12.6 percent more likely to have a fire than a frontally
damaged car.

Cars, with an odds ratio of ¥ = 0.790 for damage to the side, are Jess sensitive than light
trucks ¥ = 1.050, and vans ¥ = 1.074 for damage to the side. A side-damaged van in a
fatal crash is {{1.074/0.790 = 1.359] -1}*100 = 35.9 percent more likely to have a fire than
a side-damaged car. A truck with damage to the side, which is involved in a fatal crash is
{[1.050/0.790 = 1.329] -1}*100 = 32.9 percent more likely to have a fire than a car, with
damage to the side, which is involved in a fatal crash.

To examine the effect of the type of object struck, on dependent variable fire, the objects
have been partitioned into five categories: vehicle, narrow, fixed, overturn and other, across
vehicle types. Note that cars, with an odds ratio of ¥ = 4.946 for striking a vehicle, are
more sensitive than light trucks ¥ = 3.558, or vans ¥ = 3.455 for striking a vehicle. A car
that struck a vehicle in a fatal crash is {[4.946/3.455 = 1.432] -1}*100 = 43.2 percent more
likely to have a fire than a van, which struck another vehicle. A car that struck another
vehicle in a fatal crash is {[4.946/3.558 = 1.390] -1}*100 = 39.0 percent more likely to
have a fire than a truck that struck a vehicle.

Cars, with an odds ratio of ¥ = 8.024 for striking a narrow object such as a telephone pole,
are more sensitive than light trucks ¥ = 7.747, and vans W = 7.451 for striking a narrow
object. A car that struck a narrow object in a fatal crash is {[8.024/7.451 = 1.077] -1}*100
= 7.7 percent more likely to have a fire than a van that struck a narrow object. A car that
struck a narrow object in a fatal crash is {[8.024/7.747 = 1.036] -1}*100 = 3.6 percent
more likely to have a fire than a truck, which struck a narrow object, which is involved in a
fatal crash.

Cars, with an odds ratio of ¥ = 6.661 for striking a fixed object such as a wall, are more
sensitive than light trucks ¥ = 5.116, and vans Y = 5.072 that struck a fixed object. A car
that struck a fixed object in a fatal crash is {[6.661/5.072 = 1.313] -1}*100 = 31.3 percent
more likely to have a fire than a van that struck a fixed object. A car that struck a fixed
object in a fatal crash is {[6.661/5.116 = 1.302] -1}*100 = 30.2 percent more likely to
have a fire than a truck that struck a fixed object.

- 63 -


Statistical Models

An empirical statistical model proves useful to approximate the response (fire/MHE fire)
over the limited ranges of available variables. The models separate the effects of the input
variables and permit one to examine the net effect of a variable on fires/MHE fires, holding
all other variables in the model constant. Many models were estimated to examine the
effects on fire/MHE fire for cars, light trucks and vans. Models that contain the Statistically
significant predictor variables are evaluated for both fire and MHE fire. Overall models
include a set of dichotomous variables that account for the differences among vehicle types.
In addition, models for each vehicle type were estimated. Although many improvements
have been made in vehicle design over the time period of this study, much of this
information is not contained in the available data bases and therefore was not considered in
this analysis.

The results of the modeling effort are expressed in terms of the odds ratio denoted by the
Greek letter psi, ¥. The odds ratio, Y, is the quotient of the odds, i.e., the odds ratio of the
odds 10 to 1 is 10/1 = 10.0. The odds ratio of 2 to 5 is 2/5 = 0.4. An odds ratio of 2
means that it (fire/MHE fire) is twice as likely to occur in the presence vs. the absence of
the particular characteristic (e.g., rear impact, impact with a narrow object, etc.). The
percentage increase/decrease is defined by the equation (odds ratio - 1) * 100. If the odds
ratio of an independent variable is 1, then the dependent variable (fire/MHE fire) is not
sensitive to changes of the independent variable. The closer an odds ratio is to 1 (using a
multiplicative scale; the logarithm of the scale is a conventional metric) the less sensitive the
dependent variable is to changes in the independent variable.

To obtain the odds ratio, one exponentiates the estimated model coefficient, denoted by the
Greek letter beta, i.c., W = e*, (i.e., the estimated change in the log of the odds ratio). The
probability that 8, and thus ¥, occurred by chance is denoted by p. The requirement for
including a variable in the analysis of the base model was that p would be less than 0.05;
that is, the probability that 8 was statistically significantly different from zero, which is
equivalent to ¥ being statistically different from 1, was at least 0.95. In order to compare
odds ratios across vehicle specific models, if a variable was included in the base model and
could be included in the vehicle specific models, it was, even if Pp was larger than 0.05. The
models required the use of some polytomous variables, i.e., more than two States, €.g.,
vehicle type (cars, light trucks, and vans). The polytomous variables were coded as a set of
dichotomous variables. The number of dichotomous variables required to consider all levels
is one less than the number of levels of the polytomous variable. For example, vehicle type
(cars, light trucks and vans) has three levels. Therefore, two dichotomous variables are
needed to represent the polytomous variable vehicle type, where the omitted variable is
implicitly included as the "reference group". All relationships for this group of variables are
expressed as being relative to the reference group. Thus, if two vehicle type variables are
included for light trucks and vans, observed relationships are stated as the odds ratio of fire
occurrence for light trucks relative to cars and vans relative to cars, all other things being
equal. In the event that one of the dichotomous variables in the set is included in the model,
all dichotomous variables for the selected polytomous variable were included.

- 56 -



Exhibit 36
AREA OF DAMAGE - LIGHT TRUCKS

Number Percent Number Percent ~ |
Fire Fire MHEF MHEF
Trucks Trucks Trucks Trucks
603 2.57 208 0.89
1270 2.70 419 0.89
52 1.87 17 0.61
271 2.68 98 ar]
| Other 3419 84 2.46 | 33 0.97 |
Exhibit 37

95 PERCENT CONFIDENCE LIMITS FOR AREA OF DAMAGE - LIGHT TRUCKS

Percent Upper
Fire Limit

2.35 2.57 2.79
2.54 2.70 2.85

Rollover

Rear 1.35 1.87 2.43 0.30 0.61 0.93
Side 2.35 2.68 3.01 0.77 0.97 1.17
Other | 1.92 | 2.46 2.98 0.63 0.97 | 1.31

There are approximately twelve times as many fires/MHE fires involving vans with damage
to the front as vans involving rear damage. However, the rates of occurrence of fire/MHE

fire are somewhat higher for vehicles with rear damage vs. front damage, namely, 2.73
percent/0.76 percent vs. 1.81 percent/0.54 percent, see Exhibits 38 and 39.

-33-


of different vehicle types in slightly different ways. Cars, with an odds ratio of ¥ = 0.521,
are the most sensitive to the number of vehicles involved in the crash. Light trucks, with an
odds ratio of ¥ = 0.651, are least sensitive and vans, with an odds ratio of ¥ = 0.589, are
between cars and light trucks. A crash of a van involving no other vehicle vs. a crash of a
car involving no other vehicle is 12.4 percent [{(0.586/0.521) = 1.124) -1}*100] more likely
to have a MHE fire than a multiple-vehicle van crash vs. a multiple-vehicle car crash. A
crash of a truck involving no other vehicle vs. a crash of a car involving no other vehicle is
24.9 percent ({(0.651/0.521) = 1.249 -1}*100] more likely to have a MHE fire than a
multiple-vehicle truck crash vs. a multiple-vehicle car crash.

The area of damage, i.e., the location of damage (rear, front, or side) seems to produce
different rates of MHE fire across vehicle types. Cars, with an odds ratio of ¥ = 2.068 for
damage to the rear, are more sensitive than light trucks ¥ = 0.588, and vans ¥ = 1.432 for
damage to the rear. A car with damage to the rear in a fatal crash is 44.4 percent,
[{(2.068/1.432) = 1.444 -1}*100}, more likely to have a MHE fire than a van with damage
to the rear in a fatal crash. A car with damage to the rear in a fatal crash is 251.7 percent
{{(2.068/0.588) = 3.517 -1}*100] more likely to have a MHE fire than a truck with damage
to the rear in a fatal crash.

Cars, with an odds ratio of ¥ = 0.471, for damage to the front, are relatively less likely to
have a MHE fire than light trucks with an odds ratio of Y = 0.676, or vans with an odds
ratio of ¥ = 0.936 for damage to the front. A van receiving frontal damage in a fatal crash
is 98.7 percent [{(0.936/0.471) = 1.987 -1}*100] more likely to have a MHE fire than a
frontally damaged car. A frontally damaged truck in a fatal crash is 86.1 percent
{{(0.936/0.471) = 1.861 -1}*100] more likely to have a MHE fire than a frontally damaged
car.

Cars, with an odds ratio of ¥ = 0.339 for damage to the side, are relatively fess likely to
have a MHE fire than light tricks with an odds ratio of ¥ = 0.624, or vans with an odds
ratio of ¥ = 0.912 for damage to the side. A side-damaged van in a fatal crash is 46,2
percent ({(0.912/0.624) = 1.462 -1}*100] more likely to have a MHE fire than a side-
damaged car. A truck with damage to the side, which is involved in a fatal crash is 84.1
percent [{(0.624/0.339) = 1.841 -1}*100] more likely to have a MHE fire than a car, with
damage to the side, which is involved in a fatal crash.

To examine the effect of the type of object struck on MHE fire, the objects have been
partitioned into categories; vehicle, narrow, fixed, and overturn; across vehicle types. Note
that cars, with an odds ratio of ¥ = 5.964 are more likely to have a MHE fire following
striking a vehicle, than light trucks with an odds ratio of ¥ = 5.061, or vans with an odds
ratio of W = 2.565. A car that struck a vehicle in a fatal crash is 132.5 percent
[{(5.964/2.565) = 2.325 -1}*100] more likely to have a MHE fire than a van, which struck
another vehicle. A car that struck another vehicle in a fatal crash is 17.8 percent
[{(5.964/5.061) = 1.178 -1}*100] more likely to have a MHE fire than a truck that struck a
vehicle.

Cars, with an odds ratio of ¥ = 10.207 are relatively less likely to have a MHE fire if they
strike a narrow object such as a telephone pole than light trucks with an odds ratio of ¥ =
14.249, or vans with an odds ratio of YW = 12.890. A van that struck a narrow object in a
fatal crash is 26.3 percent [{(12.890/10.207/) = 1.263] -1}*100] more likely to have a MHE

- 67 -


Salt Effect

The effect of using salt and similar products under conditions of snow and ice may contribute
to vehicle corrosion and an increase in the risk of fire/MHE fire. The fifty states and the
district of columbia have been partitioned into three groups; salt belt states, sun belt states
and other states. The rate of fire and most harmful event fire for the salt belt states is
compared to the rates for the sun belt states. The states of Connecticut, Illinois, Indiana,
Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York,
Ohio, Pennsylvania, Rhode Island, Vermont, West Virginia, and Wisconsin are considered
the “salt belt" states. For purposes of this study the sun belt states are defined to be
Alabama, Arizona, Florida, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, South
Carolina, and Texas. The remaining states and the District of Columbia are considered the
other states.

Vehicles are identified by the state of registration, not the location of the crash. Foreign
registered vehicles, unregistered vehicles, U.S. Government registered vehicles, etc., are not
counted. Cars registered in a state using large amounts of salt and other corrosive materials
on their roadways have approximately a 25 percent higher rate of occurrence of fires than do
cars in the sun belt states. However, cars registered in the salt belt states are approximately
40 percent less likely to have a fire identified as the MHE as a car registered in sun belt
states. A total of 2676 cars from the salt belt states experienced a fire. There were 1575
crashes involving a car from the sun belt states that had a fire. There were 478 cars from
the salt belt states, which were identified as having a fire as the MHE. A total of 609 cars
from sun belt states were identified as having a fire as the MHE. See Exhibits 65 and 66 for
the results. The decrease in the MHE fire for salt belt states compared to sun belt states was
not anticipated. To check the results the analysis was repeated with the additional
requirement that the vehicle age would be at least five years old. Vehicles newer than this
would likely not show the signs of corrosion. However, the results were approximately the
same.

Exhibit 65
SALT EFFECT - CARS

Number
MHEF
Cars

Salt Belt
Sun Belt

- 50 -


Exhibit 48
OCCURRENCE OF FIRE - LIGHT TRUCKS
OBJECT STRUCK Partitioned by AREA OF DAMAGE

Damaged Vehicle Narrow Fixed Other Overturn
Area

Rollover 215 78 198 11 101
Front 769 249 202 48 2 |

Rear 45 2 2 3 0

Side 156 67 31 17 0

Other 39 18 13 ll 3

1224 4l4 446 90 106

Exhibit 49

OCCURRENCE OF MOST HARMFUL EVENT FIRE - LIGHT TRUCKS
OBJECT STRUCK Partitioned by AREA OF DAMAGE

Fixed Other Overturn
|

Rollover 56 30 85 4 33
Front 189 124 94 10 2
Rear 14 1 1 1 0
Side 50 35 ll 2 0
Other 10 7 6 8 2
Total 319 197 197 25 37

-39-


Exhibit 1

14

MICHIGAN NON-FATAL PERSONAL INJURY FIRE Crashes in VANS

by IMPACT AREA
Impact Total Injury Number Lower 95% Percent Upper 95%
Area Crashes Fires Limit Fire Limit

Front 9621 35 0.24 0.36 0.48
Rear 4778 6 0.03 0.13 0.23

Side 2519 0.10 0.32 0.54
Other 1934 13 0.31 0.67 1.04

Exhibit 115

MICHIGAN PROPERTY DAMAGE ONLY FIRE Crashes in VANS by IMPACT AREA

Impact Total Number Lower 95% Percent Upper 95%
Area Crashes Fires Limit Fire Limit

Front 61662 69 0.09 0.11 0.14

Rear 37621 31 0.05 0.08 0.11

Side 16772 18 0.06 0.11 0.16

Other 4125 75 1.41 1.82 2.23

- 83 -


Exhibit 108

MICHIGAN NON-FATAL PERSONAL INJURY FIRE Crashes in CARS

by IMPACT AREA

Impact Total Injury Number Lower 95% Percent Upper 95%
Area Crashes Fires Limit Fire Limit _|j
| Front 362604 1162 0.30 0.32 0.34
Rear 170888 236 0.12 0.14 0.16
Side 99270 173 0.15 0.17 0.20
C Other | 47071 192 0.35 0.41 0.47
Exhibit 109

MICHIGAN PROPERTY DAMAGE ONLY FIRE Crashes in CARS by IMPACT AREA

Impact Total Number Lower 95% Percent Upper os |
Area Crashes Fires Limit Fire Limit
Front — 1578187 1676 0.10 0.11 0.11
Rear 681155 620 0.08 0.09 0.10
Side 383934 327 0.08 0.09 0.09 |
L Other 81307 1370 1.60 1.98 1.77
Exhibit 110
MICHIGAN FATAL FIRE Crashes in TRUCKS by IMPACT AREA
Impact Total Fatal Number Lower 95% Percent Upper 95% |
Area Crashes Fires Limit Fire Limit
Front | 750 1 6.60 8.95 11.29
Rear 28 i 0.00 3.57 10.45
sac | 148 6 0.88 4.05 7.23
Other 266 4 0.04 1.50 2.97 |

-81-


Exhibit 101
MICHIGAN FREQUENCY POINT OF IMPACT
PROPERTY DAMAGE ONLY - VANS

Leak | Fire Leak &
Only Only Fire
Front 116 53 16
22 9
Side sacl 17 1
Other | 71 70_| 5
Exhibit 102

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - VANS

No Leak
No Fire
a Front 0.19 0.09 0.03 99.70 |
Rear 0.25 0.06 0.02 99.67
Side 0.28 0.1 0.01 99.61
Other | 1.72 1.7 0.12 96.46 |
Exhibit 103

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
PROPERTY DAMAGE ONLY - VANS

aa ieee —

Low % Up Low] % Up Low Fire | Up

Lim | Leak | Lim Lim | Fire | Lim Lim | Leak i
—1 —1

0.19

0.22

0.06

0.30

0.03

0.36

0.05

2.12

As with cars and trucks the Michigan data for vans may be combined to provide information

for all reported crashes.

The results are:

- 78 -


extrication may be more prevalent in severe crashes. In addition extrication is performed at
the person level not the vehicle level. Note that the fire rate and MHE Fire rate
approximately doubles if extrication is involved. The results are found in Exhibit 73.

Exhibit 73
EXTRICATION
Extrication Fire No Percent MHE MHE | Percent
Status in Fire Fire Fire Not MHE
Vehicle Fire Fire

Extricated 2161 43633 4.72 582 | 45212 1.27

a Not extricated 13550 | 607666 2.18 4107 | 617109 0.66
Unknown 467 10017 4.45 114] 10370 1.09

- 55 -


Exhibit 104
MICHIGAN FREQUENCY POINT OF IMPACT
ALL REPORTED CRASHES - VANS

—]
Impact Fire Leak & No Leak
Only Only Fire No Fire
Front 82 25 41042
Rear 183 26 13 42186
Side 94 21 5 19190
r Other 139 79 10 sea |
Exhibit 105

MICHIGAN PERCENTAGE RATE POINT OF IMPACT
ALL REPORTED CRASHES - VANS

Exhibit 106

by POINT OF IMPACT
ALL REPORTED CRASHES - VANS

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE

Impact || Low % Up | | Low| % Up Low | Fire | Up
Area Lim | Leak | Lim Lim } Fire | Lim Lim | Leak | Lim
Front |} 0.27 | 0.32 | 0.36 0.09 | 0.11 | 0.14 0.02 | 0.04 | 0.05
Rear || 0.37 | 0.43 | 0.49 0.04 | 0.06 | 0.08 0.01 | 0.03 | 0.05
L Side } 0.39 | 0.49 | 0.58 0.06 | 0.11 | 0.16 0.00 | 0.03 | 0.05
Other | 1.91 | 2.28 | 2.66 1.01 | 1.30 [1.58 0.06} 0.16 | 0.27

-79-



extrication may be more prevalent in severe crashes. In addition extrication is performed at
the person level not the vehicle level. Note that the fire rate and MHE Fire rate
approximately doubles if extrication is involved. The results are found in Exhibit 73.

Exhibit 73
EXTRICATION
—— ,
Extrication Fire No Percent MHE MHE | Percent
Status in Fire Fire Fire Not MHE
Vehicle Fire Fire
SS
[ Extricated 2161 43633 4.72 582 45212 1.27
Not extricated 13550 | 607666 2.18 4107 | 617109 0.66
L Unknown 467| 10017 4.45 114} 10370] 1.09

-55 -


There are relatively few 1978 and newer model year light trucks involved in fatal crashes
(especially those with fire/MHE fire) in the early 1980's that one should not automatically
conclude that there has been a significant decrease in the occurrence of fire or MHE fire.

The results are in Exhibits 3 and 4.

Exhibit 3

YEAR OF CRASH - 1978 MODEL YEAR AND LATER LIGHT TRUCKS

Number Percent Number Percent
Fire Fire MHEF MHEF
Trucks Trucks Trucks Trucks
87 3.29 32 1.21
97 2.74 47 1.33
1 2.76 42 1,04
90 2.36 4l 1.07
90 2.19 33 0.80
114 2.39 42 0.88
126 2.31 40 on |
156 2.51 44 0.71 |
179 2.56 63 0.90
219 2.74 16 0]
233 2.79 75 0.90
231 2.67 16 0.88
284 2.82 93 0.92
263 2.57 7h 0.69



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Exhibit 117
MICHIGAN FIRE RATE BY VEHICLE AGE

- 85 -


Year of the Crash

The first variable to be reported is the year of the crash. The number of vehicles involved in
fatal crashes, the number of fire occurrences, the number of MHE fires, the raw percentage
rate of occurrence of fire and MHE fire for cars, partitioned by year of the crash appears in
Exhibits 1 and 2. Neither fire nor MHE fire exhibits an increasing trend or a decreasing
trend over time for cars, light tracks, or vans. Since the vehicles in this study are restricted
to 1978 and newer vehicles there are relatively few vehicles in the data base for early years
of the study. The results are:

Exhibit 1
YEAR OF CRASH - 1978 MODEL YEAR AND LATER CARS

Year Cars Number Percent Number Percent
of in Fatal Fire Fire MHEF MHEF
Crash Crashes Cars Cars Cars Cars
1979 T165 168 2.34 54 0.75
1980 10061 246 2.45 88 0.87
[ 1981 12889 303 2.35 109 0.85
1982 13248 284 2.14 91 0.69
1983 14902 351 2.36 117 0.79
1984 17638 397 2.25 112 0.63
1985 20121 403 2.00 106 0.53
1986 22859 552 2.41 167 0.73
1987 25575 626 2.46 193 0.75
1988 28031 716 2.55 192 0.68
1989 28583 666 2.33 178 0.62
1990 28655 726 2.53 194 0.68
1991 27325 746 2.73 197 0.72 }
| 192 26546 667 2.51 157 0.59 |



Exhibit 88
95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
ALL REPORTED CRASHES - CARS

—}

Low Fire Up

Area i Leak | Lim Lim | Leak Lim
— }

Front || 0.32 | 0.33 | 0.34 0.12 | 0.12 | 0.13 0.03 | 0.03 0.03 |

Rear || 0.40 | 0.41 | 0.43 0.07 | 0.08 | 0.08 0.02 | 0.03 0.03 |
Side || 0.34 | 0.35 | 0.37 0.08 | 0.09 | 0.10 0.02 | 0.03 oun |

other | 1.77) 1.85 | 1.92 1.04 | 1.09 | 1.15 0.11 | 0.13 0.15

Crash-involved light trucks involving personal injury, with damage to the rear, have fewer
fires and a lower rate of fire than any other impact area (Exhibits 89 and 90). This is
consistent with the FARS data, Exhibit 36.

Exhibit 89
MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - LIGHT TRUCKS

Leak & No Leak
Fire No Fire
159 66 42659
19 7 17640
17 10 10268
35 15 13059 |

-73-


Exhibit 32

OCCURRENCE OF FIRE - CARS
AREA OF DAMAGE PARTITIONED BY WEIGHT CLASS

Weight Rollover im Front Rear Side Other 1

Class jo

Class 1 84 164 43 53 17

Class 2 312 785 130 261 77

Class 3 331 704 163 287 1

Class 4 407 904 169 327 69

Class 5 146 378 67 116 45

Class 6 156 340 68 123 58

Total 1436 3275 640 1167 336
Exhibit 33
PERCENT OF FIRE - CARS
AREA OF DAMAGE PARTITIONED BY WEIGHT CLASS

Weight Rollover Front re | Side Other |

Class

Class 1 2.19 1.65 4.97 1.26 2.38

Class 2 2.38 2.12 4.53 1.53 3.28

Class 3 2.99 2.10 5.85 1.76 3.30

Class 4 4.61 2.38 6.16 2.24 2.95

Class 5 5.33 2.03 5.24 1.95 4.20
= 6 3.75 2.06 5.05 2.08 cel
| Total | 3.28 2.13 5.38 1.82 3.11

-31-


There is no apparent increase or decrease of fires/MHE fires for light trucks with increasing
age. The results appear in Exhibits 17 and 18.

VEHICLE AGE in YEARS - 1978 MODEL YEAR AND LATER LIGHT TRUCKS
Truck Trucks Number Percent Number
Age in Fatal Fire Fire MHEF
Years Crashes Trucks Trucks | Trucks
=<

0 10993 294 2.67 104

1 14873 378 2.54 127

2 12504 322 2.58 129

3 10310 267 2.59 96

4 8215 207 2.52 70

5 7013 183 2.61 47

6 5688 157 2.76 45

7 4612 129 2.80 42

8 3574 92 2.57 32

9 2802 81 2,89 30

10 2015 46 2.23 13

I oT 1574 45 2.78 il

12 | 1112 29 2.54 13

13 820 26 3.07 6

14 345 Il 3.09 4

-21-


Exhibit 117
Exhibit 118

Exhibit 119

Exhibit 120
Exhibit 121
Exhibit 122

Exhibit 123

Exhibit 124

Exhibit 125

MICHIGAN FIRE RATE BY VEHICLE AGE (CHART)
OCCUPANTS WITH BURN INJURIES BY VEHICLE AGE

OCCUPANTS WITH BURN INJURIES BY Crash COMPLEXITY
SINGLE-VEHICLE VS MULTIPLE-VEHICLE CRASHES

OCCUPANTS WITH BURN INJURIES BY DAMAGED AREA
OCCUPANTS WITH BURN INJURIES BY OBJECT STRUCK
OCCUPANTS WITH BURN INJURIES BY DELTA V

OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY MAXIMUM

BURN INJURY A.LS.

ENTRAPMENT

ORIGIN of FIRES

xi

-85-

-88-

-89-

-90-

-91-

-92-

-93-

-94-

-95-


errors of both estimates should be computed).

Age of Driver is the only variable that stays within the 95 percent confidence levels when the
vehicle types are examined. The second order interactions of vehicle type can be used to
account for the differences due to differences among cars, light trucks, and vans. Another
approach is used here, namely a model is built for each of the individual vehicle types. This
approach, however, does not address the remaining second order interactions. Exhibit 75,
Base Model Compared to Vehicle Specific Models - Fire, shows that there are many
differences among cars, light trucks, and vans. Perhaps the most important difference, due
to vehicle type, is that fires in cars are very susceptible to a crash involving the rear of the
car, but this is not so for light trucks or vans. A detail commentary for the variables
follows.

To examine the effect of vehicle age across vehicle type note that cars, with an odds ratio of
¥ = 1.031, are the most sensitive to the age of the vehicle. Light trucks, with an odds ratio
of ¥ = 1.010, are less sensitive to vehicle age than are cars, and vans, with an odds ratio of
WY = 1.006, are the least sensitive to vehicle age. For vehicles involved in fatal crashes, a
ten-year difference in the age of a car vs. a ten-year difference in the age of a van raises the
relative rate of a fire in a car vs. a fire in a van by {[(1.031/1.006)° = 1.278] -1}*100 =
27.8 percent. A ten-year difference in the age of a car vs. a ten-year difference in the age of
a light truck raises the relative rate of a fire in a car vs. a fire in a truck by {[(1.031/1.010)"
= 1.228] -1}*100 = 22.8 percent.

The effect of the time of day, night vs. day, is not uniform across vehicle types. Note that
cars, with an odds ratio of ¥ = 1.589, are the most sensitive to the time of day. Light
trucks, with an odds ratio of Y = 1.396, are less sensitive and vans, with an odds ratio of ¥
= 1.377, are the least sensitive. The relative rate of fire in a car at night vs. a van at night
is {[1.589/1.377 = 1.154] -1}*100 = 15.4 percent higher.

The speed limit has different effects on the odds ratio across vehicle types. Note that cars,
with an odds ratio of 1.032 per mph, are the least sensitive to changes in the posted speed
limit. Light trucks and vans, with an odds ratio of 1.050 per mph, are more sensitive to
changes in the speed limit. A ten mph difference in the speed limit for a light truck or van
vs. a ten mph difference in speed limit for car raises the relative rate of a fire in a light truck
or van vs. a fire in a car by {[(1.050/1.032/) = 1.189] - 1}*100 = 18.9 percent.

Single-vehicle crashes vs. multiple-vehicle crashes affect vehicle types in slightly different
ways. Cars, with an odds ratio of ¥ = 0.773, are the most sensitive to multiple-vehicle
crashes. Light trucks, with an odds ratio of ¥ = 0.976, are less sensitive and vans, with an
odds ratio of ¥ = 0.979, are the least sensitive. A crash of a car involving no other vehicle
vs. a crash of a van involving no other vehicle is 21.0 percent [{(.773/0.979) = 0.790] -
1}*100] less likely to have a fire than a multiple-vehicle car crash vs. a multiple-vehicle van
crash. A crash of a truck involving no other vehicle vs. a crash of a car involving no other
vehicle is 25.8 percent [{(0.973/0.773) = 1.258] -1}*100] more likely to have a fire than a
multiple-vehicle truck crash vs. a multiple-vehicle car crash.

The area of damage, i.e., the location of damage (rear, front, or side) seems to produce

different rates of fire across vehicle types. Cars, with an odds ratio of ¥ = 2.484 for
damage to the rear, are more sensitive than light trucks ¥ = 0.936, and vans ¥ = 0.842 for

- 62 -


Exhibit 52

ROLLOVER - CARS

Rollover Cars Number Percent Number Percent
Status in Fatal Fire Fire MHEF MHEF
Crashes Cars Cars | Cars Cars
| Rollover 43718 1436 3.28 446 1.02
No Rollover 239880 5418 2.26 1509 0.63
Exhibit 53
95 PERCENT CONFIDENCE LIMITS FOR ROLLOVER - CARS
Rollover Lower Percent Upper Lower Percent Upper
Status Limit Fire Limit Limit MHEF Limit
Rollover 3.12 3.28 3.45 0.93 1.02 Lil
—|

No Rollover 2.20 2.26 2.32 0.60 0.63 0.66

In the case of cars that rollover the principal impact point, i.e. the point that produced the
most property damage or personal injury is of interest. The principal impact point has been
partitioned into the following areas: front, rear, side, non-collision, top, undercarriage,
underride, override and other. The results of the partition of rollover appear in Exhibit 54.

-41-


that model year may be confounded with vehicle age. To examine this issue the analysis in
Exhibit 7 was performed with vehicle age limited to four years as done by Malliaris and was
then repeated limiting the age of the vehicles to two years. There was no appreciable change
between limiting the age to four years and limiting the age to two years. The results of
limiting age to four years appears in Exhibit 9. The Malliaris result which showed that the
fire rate increases with older model years was not noted here. The differences in results
between this effort and that of Malliaris seem to be due to differences in model years
examined, using the entire nation as opposed to the single state of Michigan and using all
crashes in Michigan rather than the fatal crashes of this effort.

Exhibit 9
MODEL YEAR, AGE LIMITED TO FOUR YEARS - CARS

Model ma Cars Number Percent Number Percent
Year in Fatal Fire Fire MHEF MHEF
Crashes | Cars Cars Cars Cars
1978 13911 308 2.21 111 0.80
1979 16594 426 2.57 148 0.89
- 1980 13849 294 2.12 16 0.55
1981 11992 238 1.98 84 0.70
| 1982 10617 216 2.03 57 0.54
| 1983 10509 233 2.22 65 0.62
1984 14234 334 2.35 77 0.54
1985 14076 309 2.20 74 0.53
r 1986 | 14409 341 2.37 96 0.67
1987 13833 315 2.28 103 0.74 |
| 1988 13431 265 1.97 68 0.51
1989 9682 187 1.93 51 0.53
1990 5972 132 2.21 30 0.50
1991 3741 76 2.03 21 0.56
1992 1543 48 3.11 19 1.23

-13-


Exhibit 66

95 PERCENT CONFIDENCE LIMITS FOR SALT EFFECT - CARS

Salt | Lower Percent Upper Lower | Percent Upper
Status Limit Fire Limit Limit MHEF Limit
Salt Belt 2.48 2.57 2.67 0.42 0.46 0.50
Sun Belt 1.92 2.02 2.12 0.72 0.78 0.84
Other 2.40 2.50 2.59 0.77 0.83 0.89 ]

Light trucks registered in a salt belt state have approximately a 10 percent higher rate of
occurrence of fires than do light trucks in the sun belt states. However, light trucks
registered in the salt belt states are approximately 50 percent less likely to have a fire
identified as the MHE than a truck registered in a sun belt state. A total of 558 light trucks
from the salt belt states experienced a fire. There were 746 crashes involving a truck from
the sun belt states that had a fire. There were 111 light trucks from the salt belt states,
which were identified as having a fire as the MHE. A total of 330 light trucks from sun belt
States were identified as having a fire as the MHE. The details are in Exhibits 67 and 68.

Exhibit 67
SALT EFFECT - LIGHT TRUCKS

Salt Trucks Number Percent Number Percent
Status in Fatal Fire Fire MHEF MHEF
Crashes Trucks Trucks Trucks Trucks
Salt Belt 19945 558 2.80 11 0.56
Sun Belt 30300 746 2.46 330 1.09
Other 34793 914 2.63 308 0.89

Exhibit 68

95 PERCENT CONFIDENCE LIMITS FOR SALT EFFECT - LIGHT TRUCKS

Salt Lower Percent Upper Lower Percent vine |
Status Limit Fire Limit Limit MHER Limit

Salt Belt | 2.57 2.80 3.03 0.45 0.56 0.66 |
Sun Belt 2.29 2.46 2.64 0.97 1.09 1.21
Other Zz 2.46 2.63 2.80 0.79 0.89 0.98

Vans registered in salt belt states have approximately a 5 percent higher rate of occurrence of

-51-



NASS Object Struck

Cars striking narrow objects, such as utility poles, have the highest rate of burn injuries.

This is consistent with the FARS data in Exhibit 40.

Exhibit 121

OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY OBJECT STRUCK

| Cars LTV
Object Bum Total Percent Bum Total Percent
Struck Injuries Injuries Injuries Injuries

Vehicle 1312 5072247 0.03 598 911980
(23) (19445) (13) (4268)

Narrow 1180 681042 0.17 196 162940 0.12
(14) (3390) (7) (808)

Fixed 499 429128 0.12 44 156176 0.03
(10) (2027) (2) (579)

Other 0 56692 0.00 22 18734 0.12
(0) (195) qd) (83)

Overturn 650 400301 0.16 182 299762 0.06
(7) (1678) (5) (1249)

-O1-


Michigan Vehicle Age

The number of vehicles involved in reported crashes partitioned by fuel leak only, fire only,
fire and fuel leak, and neither fire nor fuel leak with the percentage of all crashes that had
either a fire only or a fire and fuel leak, as well as, the percent of crashes that had a fire
given that the crash had a fuel leak by the age of the vehicle in years appear in the

Exhibits 116 and 117. Note that, as with the FARS data, for cars, the rate of occurrence of
a fire increases as vehicles age. The Michigan rate of fire occurrence increases from 0.13
percent of all crashes in Michigan for new vehicles to 0.29 percent of all crashes for vehicles
that are thirteen (13) years old. Note that the Y-axis scale for Exhibit 117 covers a narrower
range [0 to 0.3 percent] than do the other exhibits - charts of this study [0 to 4.0 percent].

Exhibit 116
MICHIGAN - VEHICLE AGE in YEARS

Vehicle Fuel Fire Fire No Fire Percent Percent of
Age Leak Only & Fuel No Leak Any Fire given
Years Only Leak Fire Fuel Leak
0 1536 478 151 AN1729 0. 3 | 9.0
1 1864 587 156 565839 0.13 77
2 1721 597 146 522219 0.14 78
3 1695 625 161 | 497600 0.16 8.7 |
4 1863 659 163 472457 0.17 8.0
5 1848 631 137 407813 0.19 6.9
6 1558 564 111 335916 0.20 6.7 |
7 1414 483 98 266217 0.22 65 |
8 1260 398 97 198318 0.25 7A
9 1039 326 96 149184 0.28 8.5
10 848 239 57 108796 0.27 6.2
11 620 160 32 72732 0.26 4.9
12 364 87 20 42379 0.25 5.2
13 162 36 14 16801 0.29 8.0
17792 5870 1439 4128000 0.18 7.5

-84-


a

ey

BE

a Lb —— |-—

Sandel =

100"

tal

nm

ig

quer

Exhibit 11

MODEL YEAR - TRUCKS

-15-


NASS Damaged Area

NASS estimates that of the 617335 car occupants with injuries that occurred in rollover
crashes, 1020 were attributed to occupants with burn injuries caused by vehicle fires.
Rollovers have the highest rate of occupants with burn injuries, 0.16 percent for cars and a
somewhat lower rate 0.08 percent for light trucks and vans. The results are in Exhibit 120.
Note that there are over twice as many occupants with burn injuries where the front of a car
was damaged as opposed to the rear (864 vs. 383). However, the rate of occupants with
burn injuries is twice as high for damage to the rear compared to damage to the front. See
Exhibit 30 for comparison to the FARS data. One notes that the rate of occupants with burn
injuries for cars are the highest for rollover and damage to the rear. The corresponding
FARS data appear in Exhibits 36 and 38.

Exhibit 120
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY DAMAGED AREA

Cars LTV
Damaged Bum Total Percent Burn Total Percent
Area Injuries Injuries Injuries Injuries

Rollover 1020 617335 0.16 357 464007 0.08
(14) (2934) (10) (2254)

Front 864 3121016 0.03 475 646389 0.07
(13) (13251) (9) (3195)

Rear 383 660560 0.06 0 76710 0.00
(12) (1740) (0) (240)

Side 893 1757839 0.05 136 218832 0.06
(12) (7133) (6) (948)

Other 490 1586249 0.03 75 404678 0.02
(12) (6540) Q) (1597)



NASS Fire Origin

The origin of the fire is partitioned into three levels; fuel system, engine compartment and
other. In this context, the fuel system consists of the fuel tank(s), fuel supply and vent lines
and the filler neck. The engine area denotes the open or closed area which houses the
engine. For an engine area fire, the cause for the fire is inconsequential, it may be electrical
or fuel related. The fire’s relative location to the engine is the important consideration.

Note that virtually all of the fuel system fires, 1908 out of 1927 or 99.01 percent, are major
fires. If the origin of the fire is not the fuel system, then less than half of the fires are major

fires. The results are in Exhibit 125.

Exhibit 125
ORIGIN of FIRES

Fuel Percent | Engine | Percent | Other | Percent
System Fuel Area Engine Other
System Area
Minor 19 0.33 4613 80.59 1092) 19.07
Q) (36) @)
1908 28.35 4342 64.53 479 TAZ
(25) (60) (9)

- 95 -


significant and therefore, the van vs. car dichotomous variable should be included.
Interpretation of the Odds Ratios - Base Models

All statements in this section describing the outcome of the statistical models cover only
vehicles involved in fatal crashes, unless otherwise noted. The data suggest that as a vehicle
ages a fire is a more likely outcome. For each year the vehicle ages, the odds ratio increases
by a factor of 1.026. That is, everything else being equal, a vehicle that is ten years older
than another is (1.026'° - 1)*100 = 29.3 percent more likely to have a fire than the newer
vehicle. Vehicle age does not seem to affect the occurrence of MHE fire.

Model year was not found to have an appreciable effect on fires; however, model year had a
significant effect on MHE fires. For MHE fires, newer model year vehicles are less
susceptible to being classified as having fire as the MHE. A difference of ten years in model
year produces an odds ratio of 0.970'° = 0.74 for MHE fires. That is if two vehicles differ
only by ten model years the older vehicle is (0.970"° - 1)*100 = 35.1 percent more likely to
have a MHE fire than the newer vehicle.

Fire and MHE fire are both sensitive to the type of vehicle involved. A fatal crash-involved
truck is 7.5/35.1 percent more likely than a car to have a fire/MHE fire (ceteris paribus). A
van is 2.5 percent less likely than a car to have a fire. However, a van is 13.3 percent more
likely than a car to have a fire classified as MHE fire.

Vehicles driven by younger drivers are more likely to experience a fire in a fatal crash or a
fire classified as a MHE than are vehicles driven by older drivers. An increase of ten years
in driver age lowers the odds ratio to 0.991'° = 0.914 (0.992'° = 0.923) for a fire (MHE
fire). That is, the rates of fire/MHE fire increase by (.9917° - 1)*100 = 9.6 percent and
(.992"° - 1)*100 = 8.3 percent, respectively, for drivers that are ten years younger.

Vehicles in nighttime fatal crashes have higher rates of fire/MHE fire than vehicles that are
involved in fatal crashes during the day. This may be due to the greater proportion of
single-vehicle crashes that occur at night, plus the possibility of greater impact speeds
associated with the much higher rates of alcohol involvement exhibited by fatal crash-
involved drivers during the night. Vehicles involved at night are 53.1 percent/73.1 percent
more likely to have a fire/MHE fire than those involved during the day. For this study,
night is defined as 6:00 p.m. to 5:59 a.m., and day is from 6:00 a.m. to 5:59 p.m.

Fatal crash-involved vehicles on roadways with higher speed limits are associated with a
higher rate of fires and MHE fires than those on roadways with lower speed limits. Each ten
mile per hour increase in speed limit raises the odds ratio of a fire/MHE fire by (1.035 =
1.410)/(1.042 = 1.509), respectively. That is, the rate of vehicle fires rises by (1.035" -
1)*100 = 41.1 percent/(1.042"° - 1)*100 = 50.9 percent, respectively for fire/MHE fire.
Contrasting vehicles involved in fatal crashes on roads with speed limits of 30 mph to 55
mph (an increase of 25 mph), raises the likelihood of a fire/MHE fire by 136.3
percent/179.7 percent. That is, the odds ratios are 2.363/2.797, respectively.

Vehicles in multiple-vehicle fatal crashes are less likely to have a fire/MHE fire than are

vehicles in single-vehicle fatal crashes. Single-vehicle fatal crashes are (0.807' - 1)*100 = -
23.9 percent/(0.542" - 1)*100 = 84.5 percent more likely to result in a fire/MHE fire than

- 58 -


Exhibit 77

BASE MODEL COMPARED TO VEHICLE SPECIFIC MODELS - MHE FIRE

Odds Ratios
| Variable | Base Cars Cars & Trucks Vans
Model ¥ Only ¥ Weight ¥ Only ¥ Only ¥ |
Model year 0.970 0.971 0.970 0.972 0.948 |
Vehicle type
Truck vs. oe 1.351 | Cars Cars & Trucks Vans
' Van vs. Car 1,133 | Only Weight Only Only
| Age of driver 0.922 0.992 0.991 0.994 1.001
Night vs. Day 1.731 1,787 1.793 1.659 1297 |
Speed limit 1.042 1.038 1.038 1.055 1.045
Multiple-vehicle 0.542 0.521 0.521 0.651 0.586
Car weight in Ibs. N/A N/A 1.000017 N/A N/A
Area of damage |
Rollover 0.414 0.419 0.432 0.399 0.740
Rear 1.796 2.068 2.116 0.588 1,432
Front 0.527 0.471 0.476 0.676 0.936
Side 0.394 0.339 0.344 0.624 0.912
Object struck
Vehicle 5.570 5.964 5.977 5.061 2.565
Narrow 11.28 10.207 10.368 14.249 12.890
Fixed 9.122 9.047 9.243 9.651
Overturn | 2.290 2.570 2.535 2.097

In addition to the base model, Exhibit 74, models for the variable most harmful event fire,
for each vehicle type; cars, light trucks and vans were constructed. The sets of odds ratios

for each model are in Exhibit 77.

Within the Fatal Accident Reporting System (FARS) data on the weight of a car is collected.
These data are generally not available for light trucks and vans. The third column, headed
Cars & Weight, are the odds ratios for a model that contains the car weight as an additional
independent variable. The weight variable is virtually orthogonal to the vector space spanned
by the other variables and therefore there are small changes between the sets of odds ratios


Number of Vehicles Involved

The occurrence of fires/MHE fires for car single-vehicle fatal crashes is approximately
30/100 percent higher than for multiple-vehicle car fatal crashes. A total of 3114 crashes
involving a single car and no other vehicle had fire. There were 3740 cars involving a car
and at least one other vehicle, which need not be a car. A total of 1087 cars in single-
vehicle car crashes were identified as having a fire as the MHE. A total of 867 cars in
multiple-vehicle crashes were identified as having a fire as the MHE. In single vehicle
crashes usually at least one occupant of the vehicle dies. In multiple vehicle crashes, many
vehicles do not have an occupant that dies. By adding the columns of Exhibit 21 one finds
that 283598 vehicles were involved in car crashes and 6854 cars experienced a fire. This
produces a fire rate of 2.42 percent. The results are in Exhibit 21.

Exhibit 21
SINGLE-VEHICLE vs. MULTIPLE-VEHICLE CRASHES - CARS
Crash Vehicles Number Percent Number Percent
Complexity in Fatal Fire Fire MHEF MHEF
Crashes Cars Cars Cars Cars
Single 110435 3114 2.82 1087 0.98
[_ Multiple 173163 3740 2.16 867 0.50

The 95 percent upper and lower confidence limits! for categorical data were calculated for
both fire and MHE fire. As a rough approximation, if the percentage for one level is within
the 95 percent confidence level of another level then one can conclude that there is no
measurable difference in the percentages (although to be certain, the complete statistical test,
incorporating the standard errors of both estimates should be computed). The results are
presented in Exhibit 22.

Exhibit 22
95 PERCENT CONFIDENCE LIMITS FOR
SINGLE-VEHICLE vs. MULTIPLE-VEHICLE CRASHES - CARS

Crash Lower Percent Upper Lower Percent | Upper

Complexity Limit Fire Limit Limit MHEF Limit

Single 2.72 2.82 2.92 0.92 0.98 1.04

Multiple 2.09 2.16 2.23 0.47 0.50 0.53
L_ =

' Breund, John E., Mathematical Statistics, Englewood Cliffs, N.J. Prentice-Hall, Inc,
1962, Chapter 10, pp 232-233.

-25-


NASS Delta V

Delta V is often not available for NASS cases, either because some crash types (such as
rollovers) are not applicable for a delta V computation, or because some vehicles cannot be
located to determine the crush measurements and associated characteristics. In general, one
would expect that as delta V increases, the rate of occupants with burn injuries would also
increase. As additional data becomes available, this pattern may emerge. The best available
estimates based on the data to date appear in Exhibit 122.

Exhibit 122
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY DELTA V

Cars LTV
Burn Total Percent Bum Total Percent
Injuries Injuries Injuries Injuries

00-10 0 626962 0.00 0 99888 0.00
(0) (1668) (0) (400)

11-20 16 1895883 0.00 17 338271 0.01
(ql) (7312) a) (1508)

21-30 89 552587 0.02 0 101419 0.00
(3) (3478) (0) (712)

31-40 60 115386 0.05 15 15300 0.10
(4) (1114) (1) (210)

41-50 216 25006 0.86 10 6151 0.16
7) (343) qd) (81)

| Over 50 88 9602 0.92 94 1595 5.89
4) (199) G) (30)

-92-


percent, more than three times the rate for striking another vehicle, 0.51 percent. The
results appear in Exhibits 40 and 41.

Exhibit 40
OBJECT STRUCK - CARS

Object Cars Number Percent Number Percent
Struck in Fatal Fire Fire MHEF MHEF
L Crashes Cars Cars Cars Cars
| Vehicle 166511 3655 2.20 850 0.51
Narrow 28165 1303 4.63 456 1.62
Fixed 33257 1435 4.31 517 1.55
Other 40638 223 0.55 63 0.16
LL Overturn 14985 237 1.58 68 0.45
Exhibit 41
95 PERCENT CONFIDENCE LIMITS FOR OBJECT STRUCK - CARS
Object Lower Percent Upper Lower Percent | Upper
Struck Limit Fire Limit Limit MHEF Limit
—j ——
Vehicle 2.14 2.20 2.27 048} 0.51 0.55
Narrow 4.39 4.63 4.89 1.47 1.62 1.76
|__ — 4.10 4.31 4.53 1.42 1.55 1.68
Other 0.48 0.55 0.62 0.12 0.16 0.20
Overturn | 1.39 1.58 1.76 0.35 0.45 0.55

Considering objects struck by light trucks, narrow objects have the highest rate of fire/MHE
fire, namely 5.96 percent/2.84 percent, respectively. There are about three times as many
fires (1224) when a truck struck another vehicle compared to when it struck a narrow object
(414). However, the rate of occurrence of a fire when striking a narrow object, 5.96
percent, is more that twice as high as when a truck struck another vehicle, 2.61 percent.
There were 60 percent more occurrences of a truck striking another vehicle where a fire was
judged as the MHE (319) as there were light trucks striking a narrow object (197).

However, the rate of occurrence of a MHE fire for light trucks striking a narrow object,
2.84 percent, is more than four times the rate for striking another vehicle, 0.68 percent. The
results are in Exhibit 42 and 43:

- 35 -


NASS A.LS. Severity

The maximum A.I.S/ injury severity data is available in the NASS data files. Exhibit 123
has a different structure than the previous exhibits. The second and sixth columns headed
Burn Injuries contain the number of individuals who received an A.I.S. burn injury of the
listed severity. If an individual received more than one burn injury, the individual is listed
under the highest burn injury severity received. Columns three and seven headed Maximum
Injury contain the subset of the individuals that received a burn injury, but did not receive an
injury that resulted in a more severe A.I.S. code. For example, of the 896 individuals
within cars that suffered a minor burn injury due to a vehicle fire, 35 individuals or

3.91 percent did not receive any injury with a more severe A.IS. severity level.

Exhibit 123
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES
BY MAXIMUM BURN INJURY A.LS.

Cars LTV |
ALS. Bum Maximum | Percent Bum Maximum | Percent
Severity Injuries Injury Maximum Injuries Injury Maximum
Minor 896 35
@ qd)
Moderate 216 0
(3) 0)
Serious 63 63 100.00
a) qd)
Severe 0 0 N/A 0 0 N/A
(0) ©) 0) @)
Critical 409 409 100.00 36 36 100.00
i) M Q) 2)
Maximum 1954 1954 100.00 618 618 100.00
(37) (37) (14) (14)
Unknown 114 74 94.91 0 0 N/A
@) (2) (0) (0)

- 93 -


OCCUPANTS WITH VEHICLE FIRE BURN INJURIES BY VEHICLE AGE

Exhibit 118

Cars LTV
Vehicle Burn Total Percent Burn Total Percent
Age Injuries Injuries Injuries Injuries
0 290 541383 0.05 112 181280 0.06
(4) (2536) (4) (864)
1 0 701133 0.00 0 219958 0.00
(0) (3220) (0) (1079)
2 370 746616 0.05 66 223410 0.03
(?) (3275) dd) (1124)
3 43 782977 0.01 79 239269 0.03
(2) (3165) (4) (1004)
4 1358 754250 0.18 343 230655 0.15
(4) (3201) (4) (967)
5 361 720251 0.05 64 153051 0.04
I (6) (2303) QQ) (687)
6 94 689186 0.01 81 111630 0.07
(3) (2302) @) (569)
7 127 519298 0.02 0 96691 0.00
(6) (2212) (0) (395)
8 310 540005 0.06 0 72822 0.00
(7) (2078) (0) (376)
9 428 535527 0.08 191 65015 0.29
(8) (1920) 6) (279)
10 93 479164 0.02 15 54603 0.03
(3) (1836) (dy (227)
Il 0 215999 0.00 22 52303 0.04
(0) (1304) dd) (244)
12 95 221247 0.04 0 30049 0.00
(2) (936) (0) (168)
| 13 75 114640 0.07 22 45082 cas |
(2) (652) dd) (117)
14 4 62737 0.01 17 27190 0.06
ie) G51) (1) (97)

- 88 -


are vehicles in multipie-vehicle fatal crashes.

The variable, Area of damage, has been partitioned differently for fire and MHE fire. In
particular, the cases of rollover have been absorbed in the control set of cases for the output
variable fire, but not for the output variables MHE fire. To interpret the results, all values of
odds ratio, ¥, are divided by the odds ratio for being struck in the side to obtain ¥'. For
fire, the values of W’ are Rear (2.157/0.832 = 2.593) and Front (1.073/0.832 = 1.290).

For MHE fire, the new values of ¥' are Rear (1.796/0.394 = 4.558), Front (0.527/0.394 =
1.338) and Rollover (0.414/0.394 = 1.051).

The interpretation for vehicles involved in fatal crashes follows. Vehicles struck in the rear
are 159.3 percent/355.8 percent more likely to have a fire/MHE fire than a vehicle struck in
the side. Vehicles struck in the front are 29.0 percent/33.8 percent more likely to have a
fire/MHE fire than a vehicle struck in the side. There are far more crashes where the
damage to the vehicle occurs in the front rather than the rear. Consequently, there are more
fires/MHE fires in crashes where the damage to the vehicle occurs in the front rather than
the rear (see the Area of Damage exhibits for cars, light trucks and vans, exhibits 30 through
39). Vehicles that rolled over are 5.1 percent more likely to have an MHE fire than a
vehicle struck in the side.

Object struck is treated in a similar way. In this case, the odds ratios, ¥, for Vehicle,
Narrow and Fixed are divided by the odds ratio for overturn. The rescaled odds ratios, ¥’,
for fire are Vehicle (4.541/1.780 = 2.551), Narrow (7.931/1.780 = 4.456), and Fixed
(6.217/1.780 = 3.493). The rescaled odds ratios, ¥', for MHE fire are Vehicle
(5.570/2.290 = 2.432), Narrow (11.280/2.290 = 4.926), and Fixed (9.122/2.290 = 3.983).

Vehicles that struck another vehicle in a fatal crash are 155.1 percent/143.2 percent more
likely to have a fire/MHE fire than are overturned vehicles. Vehicles that struck a narrow
object, such as a pole, are 345.6 percent/392.6 percent more likely to have a fire/MHE fire
than overturned vehicles. Vehicles that struck a fixed object, such as a wall, are 249.3
percent/ 298.3 percent more likely to have a fire/MHE fire than are overtumed vehicles.

Vehicle-Specific Models
In addition to the base model, Exhibit 74, models for the variable fire, for each vehicle type

(cars, light trucks and vans) were estimated. The sets of odds ratios for each model are in
Exhibit 75.

- 59 -


The occurrence of fires/MHE fires for single-vehicle van crashes is approximately 5/100
percent higher than for vans in multiple-vehicle crashes. A total of 130 crashes involving a
single van and no other vehicle had fire. There were 226 crashes involving a van and at
least one other vehicle, which need not be a van. A total of 55 crashes involving a single
van and no other vehicle were identified as having a fire as the MHE. A total of 51 crashes,
involving a van and at least one other vehicle, which need not be a van, were identified as
having a fire as the MHE, see Exhibits 25 and 26.

Exhibits 25
SINGLE-VEHICLE vs. MULTIPLE-VEHICLE CRASHES - VANS
Crash Vehicles Number Present Number Percent
Complexity in Fatal Fire Fire MHEF MHEF
Crashes Vans Vans Vans Van
Single 6284 130 2.07 55 0.88
Multiple 11635 226 1.94 51 0.44
Exhibits 26

95 PERCENT CONFIDENCE LIMITS FOR
SINGLE-VEHICLE vs. MULTIPLE-VEHICLE CRASHES - VANS

Crash | Lower Percent Upper Lower | Percent Upper
Complexity || Limit Fire Limit Limit MHEF Limit
Single 1.72 2.07 2.42 0.64 0.88 1.1
| Multiple 1.69 1.94 2.19 0.32 0.44 0.56

Weight of Cars

The Fatal Accident Reporting System (FARS) collects information on the weight of cars
involved in fatal crashes. Vehicle weight is not generally available for light trucks or vans.
The variable car weight has been partitioned into six classes based on previous applications
(e.g., "Passenger Car Weight and Injury Severity in Single-vehicle Nonrollover Crashes" ,
Partyka and Boehly, 1989, ESV Report 89-2b-O-005 and "Development of Databases in
Support of an Analysis of Fire Incidence Using the Fatal Accident Reporting System", Walz
and Klein, Sep. 14, 1993). This partition is used for this analysis and is defined in Exhibit
27 as:

-27-


Exhibit 72
PERCENT OF FATALITY ESTIMATES DUE TO FIRE BY YEAR OF CRASH

Year Minimum MHE Maximum
of Percent of Percent of Percent of
Crash Fatalities Fatalities Fatalities
| 1979 | 1.19 1.66 2.21 |
1980 [ 1.35 1.86 2.22 |
1981 1.26 1.67 2.20 |
1982 1.07 1.48 1.89
1983 1.10 1.48 1.96
1984 0.99 1.25 1,75 |
1985 0.82 1.00 1.54
1986 1.00 1.34 1.94 |
1987 1.08 1.37 1.89
1988 1.02 1.31 1.93
1989 0.96 1.27 1.83
1990 1.00 1.31 1.84
199] 1.06 1.40 1.94 |
! = 0.88 1.13 1.75 |
| I
- Mean 1.03 1.35 =
Mean 90-92 0.98 1.28 1.84

year vehicles as is Exhibit 71. The data shows a slightly decreasing trend for percentage of
deaths for all three measures over time.

Extrication

Extrication has a fundamentally different type of relationship with fire than do the previous
variables which have been examined so far. The Previous variables are expected to have a
“causal” relation with fire. That is a change in the speed limit or Object struck would most
likely change the rate of vehicle fires. However, although extrication does not cause fires
and fires do not cause extrication, the two variables may be associated. Both fire and

- 54 -


Introduction

The objective of this study was to analyze fire occurrence in fatal and less serious crashes, as
a function of crash, vehicle and driver characteristics levels that influence the likelihood of
postcollision vehicle fires. This analysis provides information to address potential changes to
Federal Motor Vehicle Safety Standard 301, Fuel System Integrity, to increase the
effectiveness of that standard in preventing postcollision vehicle fires.

The current Standard 301 became effective in 1978 and applied to passenger cars, light
trucks and vans. To prevent vehicles not meeting this standard from corrupting the data, all
vehicles analyzed in this report have a model year of 1978 or later. As a result of this
restriction, the data does not include all crashes, in which a fire occurred. This study
consists of four sections, which complement each other. The first two sections use data from
the Fatal Accident Reporting System (FARS). FARS consists of a census of all fatal crashes
and is therefore not a representative sample and contains crashes that are of the highest
severity. The first section contains raw cross tabulations of data for 1978 and later model
year vehicles. This section of univariate and bivariate analysis, examines the effects of the
data variables one or two at a time. The second section of the study also uses the FARS data
to construct multivariate statistical models which simultaneously adjust for the effects of the
included variables. Section three examines raw cross tabulations of data from the State of
Michigan. The Michigan police accident report (PAR) collects data on fuel leaks, which are
used to estimate the relationship between fires and fuel leaks. The Michigan data from 1982
to 1991 were used in this study. Section four is based on the National Accident Sampling
System Crashworthiness Data System (NASS CDS) for burn injuries from 1988 to 1993.

In 1979, FARS added a new field, the Most Harmful Event. The FARS data analysis,
including the Most Harmful Event field, from 1979 through 1992 are included in this report.
The vehicles covered by Standard 301, passenger cars, light trucks, and vans, are analyzed
separately in sections 1, 2 and 3. The NASS analysis of section 4 partitions the vehicle types
into two categories: cars and light trucks and vans.

Definition of FARS Fire Occurrence and Most Harmful! Event Fire

The Fatal Accident Reporting System has two levels of fire occurrence, recorded at the
vehicle level, which were considered in the first two sections of this analysis: the occurrence
of a fire, and the determination that the fire was the most harmful event (MHE). The
occurrence of a fire is an objective measure based on information provided in the police
accident report; i.e., a fire either occurred and was noted or it did/was not. The
determination that a fire was the most harmful event requires the personal judgment of the
FARS data analysts in each state. This determination sometimes is based on the availability
of a death certificate that includes N-codes (nature of injury) describing the injuries
contributing to the person’s death. However, most of the time this is not the case, and the
determination is based on information provided in the narrative of the police accident report.
The most harmful event field is of special importance when the first harmful event is minor,
for a particular vehicle, compared to some subsequent event. When coding the most harmful
event, fatalities take precedence over injuries, which take precedence over property damage.
If a vehicle is involved in more than one event that causes a fatality to its own occupants or
to nonmotorists, the event which causes the greatest number of fatalities to occupants of the
vehicle is chosen. If the number of fatalities for two or more events are equal, then the

-1-


Probability of a Fire given a Fuel Leak

The row of total incidents, from Exhibit 108, provides the information to calculate an overall
estimate of the Michigan conditional probability of a fire given a leak. One estimates this to
be 1439/(1439 + 17792) = 0.075 or 7.5 percent. The probabilities of a fire given a leak
were also calculated by age of the vehicle. The results suggest that fire rate given a fuel leak
is somewhat stable, 7.5 percent + 1.5 percent over the age range of vehicles examined.

The probability of a fire if no fuel leak was reported is calculated as 5870/(5870 + 4128000)
= 0.142 percent. This may be combined with the data above to calculate the odds ratio of a
fire given a fuel leak vs. a fire given that no fuel leak was reported, i.e. 7.5/0.142 = 52.8.
That is a fire was 52.8 times as likely when a fuel leak was reported as opposed to when a
fuel leak was not reported.

Note that there were (17792 + 1439 = 19231) fuel leaks, approximately 2.6 times the
number of fires (5870 + 1439 = 7309).

- 86 -


Michigan Data

Michigan collects data on fuel leaks and fires as part of their police accident reporting
system. These data are collected for any injury, including fatalities, and property damage
crashes. Michigan has partitioned the exposure data into four disjoint categories, namely:
(1) fuel leak but no fire, (2) fire but no fuel leak, (3) fuel leak and fire, and (4) no fuel Jeak
and no fire. The Michigan area of impact, (similar to the area of damage) was partitioned
into four disjoint categories: front, rear, side and other. Data were examined for the years
1982 to 1991 for 1978 and newer model year vehicles. In addition to the different time
frame over which the Michigan data were collected, there are two other distinct differences
between the Michigan data and the FARS data used in the previous sections of this report.
First the Michigan police crashes reports, on which this part of the analysis is based, collects
information on fuel leaks. Second the Michigan data contains information on all crashes for
which a police accident report was filed and is not limited to fatal crashes as is FARS.

The FARS data produce rates of fire and MHE fire considerably higher (about double) for
cars with damage to the rear than to the front of the car. However, the Michigan data for
both injuries including fatalities (Exhibits 80, 81, and 82) and property damage only crashes
for cars (Exhibits 83, 84, and 85) do not support this finding. In fact the rate of occurrence
of fire but no leak for crashes involving personal injury including death, is 0.28 percent
when the impact area is the front compared to 0.10 for impact area to the rear. This
difference may be due to the fact that a much larger percentage of less serious, i.e. not fatal,
crashes are included. See the exhibit of Michigan fatalities within cars later in this section,
Exhibit 101.

Vehicles in crashes resulting an injury; incapacitating, non-incapacitating or possible, are
more likely to have a fire, with or without a leak, than a crash where only property is
damaged, see Exhibit 81 and 84. That is, more serious crashes are more likely to have a
fire than less serious crashes.

Point of Impact
Exhibit 80

MICHIGAN FREQUENCY POINT OF IMPACT
INJURIES INCLUDING FATALITIES - CARS

Impact
Area
Front | 3687 1033 286 360749
Rear 1966 163 98 168952
Side 1170 170 72 99982
Other 1317 153 56 46208

- 69-


NASS A.LS. Severity

The maximum A.L.S/ injury severity data is available in the NASS data files. Exhibit 123
has a different structure than the previous exhibits. The second and sixth columns headed
Burn Injuries contain the number of individuals who received an A.I.S. bum injury of the
listed severity. If an individual received more than one burn injury, the individual is listed
under the highest burn injury severity received. Columns three and seven headed Maximum
Injury contain the subset of the individuals that received a burn injury, but did not receive an
injury that resulted in a more severe A.I.S. code. For example, of the 896 individuals
within cars that suffered a minor burn injury due to a vehicle fire, 35 individuals or

3.91 percent did not receive any injury with a more severe A.IS. severity level.

Exhibit 123
OCCUPANTS WITH VEHICLE FIRE BURN INJURIES
BY MAXIMUM BURN INJURY A.LS.

Cars LTV
ALS. Burm Maximum | Percent Bum Maximum Percent

Severity Injuries Injury Maximum Injuries Injury Maximum

Minor 896 35 3.91 281 141 50.18
4) qd) (8) @)

Moderate 216 0 0.00 0 0 N/A
(3) (0) (0) 0)

Serious 63 63 100.00 107 93 86.92
a) qd) 4 3)

Severe 0 0 N/A 0 0 N/A
(0) ©) ©) ©

Critical 409 409 100.00 36 36 100.00
7) (7) Q) (2)

Maximum 1954 1954 100.00 618 618 100.00
GBD) G7) (14) (14)

Unknown 114 74 94.91 0 0 N/A
Q) (2) (W) 0)

- 93 -


Exhibit 93
MICHIGAN PERCENTAGE RATE POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS

Impact | Leak Fire Leak & No Leak
Area Only Only Fire No Fire
| Front | 0.17 0.07 0.02 99,74
Rear 0.17 0.07 0.02 99.74
Side 0.40 0.06 0.02 99.52
Other 1.60 0.99 0.12 97.29
Exhibit 94

95 PERCENT CONFIDENCE LIMITS FOR PERCENTAGE RATE
by POINT OF IMPACT
PROPERTY DAMAGE ONLY - LIGHT TRUCKS

Impact || Low % Up Low % Up Low | Fire Up

Area Lim | Leak | Lim Lim | Fire | Lim Lim { Leak | Lim
Front |} 0.16} 0.17 | 0.19 0.06 | 0.07 | 0.08 0.01 | 0.02 {| 0.02
Rear |} 0.15 | 0.17 | 0.20 0.05 | 0.07 | 0.08 0.01 | 0.02 on
Side }| 0.35 | 0.40 | 0.44 0.04 | 0.06 | 0.08 0.01 | 0.02 | 0.03
Other J} 1.44} 1.60 | 1.76 0.87 | 0.99} 1.11 0.08 | 0.12 | 0.17

All the Michigan truck data can be combined to obtain the results for all reported Michigan

tnuck crashes with the same caveats that one has for cars.

Exhibit 95
MICHIGAN FREQUENCY POINT OF IMPACT
ALL REPORTED CRASHES - TRUCKS

Impact Leak Fire Leak & No Leak

Area Only Only Fire No Fire
Front 1188 349 123 329632
Rear 426 109 36 162904
Side 553 60 25 79824
Smet 963 276 45 36746

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