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Vehicle Size and Driver Perceptions of Safety
J. A. Thomas and D. Walton
Opus Central Laboratories, Lower Hutt, New Zealand
ABSTRACT
A sample of 496 car and sport utility vehicle (SUV) drivers responded to question-
naires that examined attitudes toward vehicle size and safety. The aim of this
research is to determine whether drivers perceive larger vehicles to be safer and
whether this concern for safety motivates drivers to purchase SUVs. Alternatively,
non–safety influences are also examined, including environmental concern,
vehicle power, prestige, and vehicle utility. Perceptions that large vehicle are
safer, off-road use, and prestige all relate strongly to SUV use. The safety arguments
raised by SUV drivers appear to be based on an egocentric concern for ‘‘bigger is
safer’’ rather than a broader understanding of vehicle fleet safety. To encourage
sustainable transport, it is suggested that road safety policy should shift drivers’
concerns from personal collision protection to overall road user protection.
Key Words: driver, risk perception, safety, SUV, vehicle size.
1. INTRODUCTION
Despite concerns for fuel efficiency and a relatively unrestricted range of vehicle
types, the New Zealand vehicle fleet has an increased trend toward larger vehicles
(MOT, 2006).
1
Mean engine size, a surrogate for mean vehicle mass, has increased
in New Zealand from 1.9 L to 2.1 L since 1990 (MOT, 2006). A similar trend is
observed in overseas vehicle fleets, with concern being raised for the popularity
of SUVs (Davis and Truett, 2000; ATSB, 2002; Plaut, 2004). SUVs are typically hea-
vier in mass than other cars and consequently present a greater safety risk to other
road users (Davis and Truett, 2000; Wenzel and Ross, 2005), have a higher fuel
consumption, and produce a higher level of pollutant emissions than do lighter
vehicles (Beydoun and Guldmann, 2006).
The recent popularity of SUVs and other large vehicles could be explained by a
public perception that bigger is better in the context of vehicle safety (Davis and
1
New Zealand vehicles are mostly used-vehicles imported from Japan.
Received 24 May 2006; revised 22 November 2006; accepted 12 March 2007.
Address correspondence to J. Thomas, Opus Research, P.O. Box 30 845, Lower Hutt,
Wellington, New Zealand. E-mail: jared.thomas@opus.co.nz
260
International Journal of Sustainable Transportation, 2:260–273, 2008
Copyright #Taylor & Francis Group, LLC
ISSN: 1556-8318 print=1556-8334 online
DOI: 10.1080/15568310701359015
Truett, 2000; Green, 2000; Plaut, 2004; Raimond, 2005; Wenzel and Ross, 2005).
This perception may stem from a set of naı
¨ve physics heuristics (see Kozhevnikov
and Hegarty, 2001) that fail to consider wider safety implications and are rein-
forced by advertising campaigns (Davis and Truett, 2000; Bradsher, 2004) and spe-
cific accident scenarios showing the benefits of larger mass in two-vehicle
collisions. The relative mass argument demonstrates that occupants of heavier
cars have a lower risk in two-vehicle collisions relative to occupants of lighter
cars (Tay, 2002; Evans, 2004; Wenzel and Ross, 2005).
Advertising campaigns promote SUVs as safe, spacious, and comfortable (Davis
and Truett, 2000; Bradsher, 2004). The SUV is marketed as fashionable, relating to
an active ‘‘outdoor’’ image and high-income lifestyle (Davis and Truett, 2000). The
utility of the SUV is also promoted, with extra storage space, the ability to go off-
road and tow heavy loads, and the capacity to carry more people (Davis and Truett,
2000; Plaut, 2004). Vehicle advertising themes focus on vehicle performance,
including the speed, power, and handling of the vehicle (Ferguson et al., 2003).
However, despite the apparent benefits, advertising companies have been cau-
tioned against promoting ‘‘limit ads’’ that show SUVs driving in extreme terrain,
performing high-speed maneuvers that exaggerate the emergency handling capa-
bilities of this vehicle type (United States Department of Justice, 2003). Recent
negative press tarnishes SUVs as antienvironment, antisafety, and suggests that
the off-road ability of these vehicles is being used by a minority of drivers
(AAMI, 2004, 2005; Bradsher, 2004).
Antisafety arguments regarding SUVs show that any safety gains from driving a
large vehicle are offset by the instability of SUVs and the reduction in safety of
smaller vehicle passengers, cyclists, and pedestrians. Wenzel and Ross (2005)
found that weight alone does not increase overall passenger safety and that a
typical SUV driver has a comparable risk to that of a car driver. For example,
larger vehicles, with a higher center of gravity, are more prone to roll-over
accidents (Kweon and Kockelman, 2003; Wenzel and Ross, 2005). From a wider
perspective, the best overall safety benefit for the occupants in a two-vehicle colli-
sion occurs when both vehicles are the same mass and when both vehicles have
a small mass (Tay, 2002). The ‘‘aggressivity’’ or relative risk to the occupants of
other vehicles in a collision is almost twice as high for SUVs compared with cars
(Wenzel and Ross, 2005). Still, the best individual occupant safety in a two-vehicle
collision is afforded to the passengers of the vehicle that has a larger mass (Tay,
2002).
Larger vehicles are typically taller and provide the driver with a higher viewpoint
and a better sight distance of the road ahead. However, Rudin-Brown (2004) found
that headway to a lead vehicle increases when the lead vehicle is large, indicating
driver compensation to the reduction in sight distance caused by the large vehicle.
Individual safety gains relative to other drivers may be regarded as ‘‘selfish safety,’’
where a driver can obtain self-protection in a larger vehicle with a higher level of
occupant safety in a multiple-car collision and a better line of sight of the road
ahead. Smaller vehicles can be considered a more altruistic alternative, with better
overall vehicle fleet safety (Wenzel and Ross, 2005), less reduction in sight dis-
tance, and a lower level of vehicle emissions. From a sustainable transport
standpoint, smaller vehicles appear to be better in the long-term. However,
Vehicle Size and Driver Perceptions of Safety
International Journal of Sustainable Transportation Vol. 2, No. 4, 2008 261
consumers appear to be driven by other motivations, with a vehicle fleet where the
average vehicle is getting larger.
The purpose of this study is to determine whether SUV drivers perceive they are
safer than are car drivers when traveling in their vehicles. A further aim is to exam-
ine whether a concern for safety motivates the vehicle size selection process. Atti-
tudes toward vehicle size and safety, vehicle characteristic preferences, naı
¨ve
knowledge of collisions, and self-reported driver risk taking behaviors, such as over-
taking behavior, are examined to test the safety motivations of car and SUV drivers.
It is expected that if safety concerns motivate vehicle size selection decisions, then
SUV drivers will be more knowledgeable about the relative mass argument and
believe that there is a strong positive relationship between vehicle size and passen-
ger safety. Awareness of vehicle safety may also lead to an increase in perceived
safety and a consequent increase in risk-taking behavior. Alternative explanations
for the popularity of SUVs that are not motivated by concern for passenger safety
are also examined. These include the utility of the vehicle (Davis and Truett,
2000), vehicle performance (Ferguson et al., 2003), lower environmental concern
(Plaut, 2004), and the prestige and status that may be associated with larger, more
expensive vehicles (Ellaway et al., 2003).
2. METHOD
2.1. Participants
A questionnaire was mailed to a sample of 288 SUV drivers and 283 car drivers
from the Wellington region in New Zealand. Table 1 shows the means (M) and
standard deviations (SD) of the car and SUV driver groups for a range of relevant
demographic and household items. The results of independent samples t-tests and
chi-square tests reveal significant differences between the samples such that SUV
Table 1. Demographic and household characteristics for the car and SUV driver
samples.
Demographic and
household items
Car SUV
MSDMSDSignificance
Age (years) 46.50 14.90 44.20 11.50
Gender (1 ¼male; 2 ¼female) 1.46 0.50 1.37 0.48
Household income (NZ$) 70,200 26,910 85,800 23,650
Number of motor vehicles
in household
1.77 0.76 1.96 0.84
Distance traveled annually (km) 15,500 7560 18,400 8395
Driving experience (1 ¼1–10 years
experience; 2 ¼more than 10 years
experience)
1.89 0.31 1.96 0.20
Age of primary vehicle (years) 9.44 4.55 8.17 4.39
Number of children 0.59 0.90 0.97 1.08
p<0.05, p<0.01, p<0.001.
J. A. Thomas and D. Walton
262 International Journal of Sustainable Transportation Vol. 2, No. 4, 2008
drivers are more likely to be male, have more children and vehicles in their house-
hold, with newer vehicles, higher incomes, more years of driving experience, and
greater annual distances traveled by motor vehicle (Table 1).
2.2. Materials
The questionnaire has 133 items and examines attitudes toward vehicle size and
safety, household characteristics, vehicle characteristics, driver characteristics,
and other demographic information. Key items focused on vehicle size and
safety, reported driving behavior, driving infringements, car purchase decision
making, naı
¨ve physics, prestige, environmental concern, and locus of control
(Rotter, 1966). Items were typically measured using 5-item Likert scales, ranging
from ‘‘1 ¼strongly disagree’’ through to ‘‘5 ¼strongly agree.’’ All scales scores
were developed using an aggregate score.
Seventeen items measured attitudes toward vehicle size, with a particular focus
on size and safety, and formed a vehicle size and safety (VSS) scale that had a
Cronbach’s alpha of 0.7. Seven items measured self-reported, safe driving beha-
vior; including seat belt use, tire pressure, warrant of fitness,
2
following distance,
hand positions on the steering wheel, overtaking behavior, and cell phone use
while driving. Five true or false items examined driving infringement history,
from ‘‘I have never had a parking ticket’’ to ‘‘I have never lost my licence (i.e.,
been disqualified from driving).’’ Ten items examined factors that Bottomley
et al. (2000) identify as likely to influence car purchase decision making, such as
performance, comfort, and fuel consumption using a 5-item scale (‘‘1 ¼very unim-
portant’’ through to ‘‘5 ¼very important’’). Six items examined knowledge of
naı
¨ve physics in the context of vehicle mass, vehicle speed, and passenger protec-
tion in collisions (see Fig. 1 for examples of the two-vehicle collision scenarios).
A naı
¨ve physics scale score was developed by assigning correct responses a score
of 1 and aggregating the six naı
¨ve physics items (giving a possible score from 0
to 6). Four items examine self–other comparisons of driver safety and consider-
ation using 11-point semantically anchored scales (e.g., ‘‘Please estimate how
safe the AVERAGE driver is’’ and ‘‘Please estimate how safe a driver YOU are’’).
Seven items (adapted from Ellayway et al., 2003) investigate the prestige (e.g.,
‘‘my vehicle is a reflection of my lifestyle’’) and feeling of protection (e.g., ‘‘I
feel I have privacy when I’m in my vehicle’’) associated with driving their vehicle.
The prestige items formed a 4-item prestige scale that had a Cronbach’s alpha of
0.71. Seven items examine environmental concern, including items examining the
concepts of futility and fatalism (Walton et al., 2003). The environmental concern
items formed a 5-item scale that had a Cronbach’s alpha of 0.8. Twenty items
(Pettijohn et al., 2005 [adapted from Rotter, 1966]) formed a scale that measured
locus of control (LOC), such as ‘‘I do not really believe in luck or chance’’ and
‘‘Other people usually control my life.’’ Drivers with a higher internal locus of con-
trol may wish to control their passenger safety by driving a vehicle they perceive is
safe. The LOC scale had a Cronbach’s alpha of 0.63 (with one item removed),
showing relatively poor internal reliability. The item ‘‘I never try anything that
2
A warrant of fitness is the 6-monthly vehicle safety inspection a vehicle must pass to be
considered roadworthy in New Zealand.
Vehicle Size and Driver Perceptions of Safety
International Journal of Sustainable Transportation Vol. 2, No. 4, 2008 263
I am not sure of’’ had a high level of disagreement (75%disagreement) and
showed low interitem correlation, so it was removed from the scale to increase
reliability and make it a 19-item scale.
2.3. Procedure
Observers were placed on the side of a 100 kph speed zone motorway into
Wellington City in New Zealand.
3
Observers recorded a sample of SUV and car
licence plates over five different weekdays during fine weather conditions. From
the address details of registered vehicle owners, a sample of 750 car drivers and
750 SUV drivers were mailed questionnaires. The response rate to questionnaires
was 38%(Car n¼288; SUV n¼283).
For the purposes of this study, SUVs were identified by several simple visual cri-
teria including passenger carrying capacity, vehicle make and model, vehicle body
3
A 100 kph speed zone is typical for urban and rural motorways in New Zealand.
Figure 1. SUV and car driver responses to three scenarios examining collisions
with vehicles of differing mass.
J. A. Thomas and D. Walton
264 International Journal of Sustainable Transportation Vol. 2, No. 4, 2008
shape, and high ground clearance. Drivers of trucks, motorbikes, and easily identi-
fiable commercial vehicles were excluded from the study.
Differentiation by perceived vehicle size was assured by self-report about the size
of a driver’s main vehicle. Example pictures of small, medium, and large vehicles
were provided to aid participant self-report regarding their vehicle’s size. Parti-
cipants were discarded if they were observed in an SUV but reported driving a
small vehicle or if they were observed in a car and reported driving a large vehicle.
This reduced the overall sample, N¼496, with 47.4%of the reduced sample driv-
ing SUVs. This reduced sample was used for all further analyses. SPSS version 11
was used to analyze the data.
3. RESULTS
3.1. Explanatory Model for Driving an SUV
A backward Wald stepwise logistic regression was used to determine the influ-
ence of the main predictor variables on SUV use. Items that revealed differences
between SUV and car drivers and were included in the logistic regression were
VSS, LOC, general environmental concern, prestige, reported driving safety, beha-
vioral safety measures (cell phone use, hand positions on the steering wheel, and
following distance to another vehicle), vehicle purchase characteristics (fuel
consumption, running and maintenance costs, space), annual driving exposure,
driving experience, off-road use, children, gender, and income.
^
gg ðSUVÞ¼10:324 þ0:129 ðVSSÞþ1:68 ðoff ¼road useÞþ0:09 ðprestigeÞ
þ0:704 ðchildrenÞþ0:345 ðincomeÞð1Þ
Equation (1) and Table 2 show the final model that explains some of the variation
between car and SUV drivers (NagelKerke r
2
[N¼431] ¼0.431, p<0.001). The
Hosmer and Lemeshow test shows that the model adequately fits the data
(X
2
[N¼431] ¼7.509, p>0.05). The interaction effects between the variables
in Equation (1) were examined following the procedure outlined in Hosmer
Table 2. Stepwise logistic regression of SUV use on key questionnaire items.
Significance
(p)
95.0%C.I. for Exp (B)
B SE Wald df Exp(B) Lower Upper
Vehicle size and
safety (VSS)
0.129 0.020 40.765 1 0.000 1.137 1.093 1.183
Off-road use 1.680 0.242 48.311 1 0.000 5.365 3.341 8.615
Prestige scale 0.090 0.048 3.549 1 0.060 1.094 0.996 1.200
Children 0.704 0.240 8.610 1 0.003 2.022 1.263 3.237
Income 0.345 0.090 14.679 1 0.000 1.411 1.183 1.684
Constant 10.324 1.233 70.122 1 0.000 0.000
Log-likelihood ¼428.111.
Vehicle Size and Driver Perceptions of Safety
International Journal of Sustainable Transportation Vol. 2, No. 4, 2008 265
and Lemeshow (2000), and the interaction effects did not improve the fit of
the model.
3.2. Perceptions of Vehicle Size and Safety
The 17 items that examined attitudes toward vehicle size, with a particular focus
on size and safety, formed a vehicle size and safety (VSS) scale that had a
Cronbach’s alpha of 0.7, indicating a reasonable level of reliability (see DeVellis,
2003 or Christmann and Aelst, 2006).
4
The 17 items are aggregated to form a
VSS score. An independent samples t-test revealed that SUV drivers (M¼53.75,
SD ¼6.33) score more highly on the VSS scale than do car drivers (M¼48.18,
SD ¼6.64), suggesting a stronger belief in larger vehicles being safer
(t[494] ¼9.543, p<0.001). Table 3 shows the means, standard deviations,
and the results of independent samples t-tests examining differences in level of
agreement for the 17 VSS scale items between car and SUV drivers.
SUV drivers are more likely than car drivers to believe in the apparent safety
benefits of large vehicles (e.g., SUVs are the safest vehicle on the road), even if
they are false. SUV drivers are also more likely to dislike the concept of driving
a small car, stating they would be unhappy driving them and believe that smaller
vehicles have limited utility. SUV drivers are less likely to recognize the overall
benefits of small vehicles if all vehicles were small.
Repeated measures t-tests examined within-subjects differences and revealed
that drivers distinguished between three characteristics of size, namely large
vehicles, heavy vehicles, and tall vehicles (see Table 3, items 8, 9, and 11). The per-
ception is that the physical size or largeness of the vehicle is more important for
occupant safety than the heaviness or mass of the vehicle (t[485] ¼6.584,
p<0.001), which is in turn more important than vehicle height (t[485] ¼
4.594, p<0.001).
3.3. Knowledge of Vehicle Size and Safety
Naı
¨ve physics items examined knowledge of passenger safety under different
collision scenarios, with four items examining two vehicles of different mass collid-
ing, one item examining vehicles colliding together traveling at different speeds,
and one item examining vehicles of different mass colliding into a stationary
wall. A naı
¨ve physics scale score was developed by assigning correct responses a
score of 1 and aggregating the six naı
¨ve physics items (giving a possible score
from 0 to 6). There was no difference between car and SUV drivers on their
naı
¨ve physics scale score (Car M¼3.32, SD ¼1.19; SUV M¼3.54, SD ¼1.17;
t[445] ¼1.933, p>0.05). Figure 1 shows collision scenarios involving two vehi-
cles of differing mass about to collide and the percentage of car and SUV drivers
that responded to the four naı
¨ve physics items examining these scenarios (the
correct answers are shown in bold font).
4
A factor analysis also revealed three latent factors that could be described as the apparent
safety benefits of large vehicles, the overall safety benefits of small vehicles, and dislike of
driving a smaller vehicle. Analysis of the underlying factors was omitted due to low scale
reliability for the second and third factors. It does suggest that vehicle size and safety atti-
tudes may not be unidimensional, as is represented in this paper.
J. A. Thomas and D. Walton
266 International Journal of Sustainable Transportation Vol. 2, No. 4, 2008
Table 3. Differences between SUV and car drivers for vehicle size and safety
(VSS) scale attitude items (ranked in order of mean difference).
Vehicle size and safety items
Car SUV
Mean
MSDMSDdifference Significance
1 Large vehicles reduce overall
safety because they decrease
the visibility for the drivers
that are following them
(Reverse item)
3.54 0.92 2.94 0.93 0.60
2 Smaller vehicles would be best
if there weren’t so many
large vehicles on the road
(Reverse item)
3.42 0.98 2.86 0.97 0.56
3 I would rather have a small
powerful car than a large
underpowered car (Reverse item)
3.52 0.96 3.06 1.01 0.46
4 I would happily drive a smaller
vehicle (Reverse item)
3.23 1.12 2.77 1.09 0.46
5 If all vehicles were small there
would be less risk of injury
in a car-to-car collision
(Reverse item)
2.81 1.03 2.49 0.99 0.32
6 Any safety advantage gained
from being in a taller
vehicle is reduced by the
instability of a higher center
of gravity (Reverse item)
3.68 0.88 3.38 0.85 0.30
7 Big old American cars are
safer than most other cars
2.54 0.97 2.5 0.93 0.04
8 Motor vehicles that are heavier
(have greater mass) offer
better protection for their
passengers in a collision
3.32 0.91 3.30 0.87 0.02
9 Larger motor vehicles offer
better protection for their
passengers in a collision
3.57 1.01 3.65 0.84 0.08
10 You are at much greater risk of
serious injury in a car-to-car
collision if you are in a small
car
3.65 0.91 3.72 0.79 0.08
11 In an accident, taller vehicles,
where the passenger is
raised further away from the
ground, offer better
passenger protection
3.00 1.06 3.15 0.96 0.16
12 My car is safer than the
average car
3.14 0.88 3.36 0.74 0.22
(Continued)
Vehicle Size and Driver Perceptions of Safety
International Journal of Sustainable Transportation Vol. 2, No. 4, 2008 267
Overall, 67%of participants recognize that the combined safety of occupants of
both vehicles is highest in a collision between two small vehicles of equal mass.
Drivers also understand the relative mass safety argument; with 85%of drivers
correctly recognizing the safety benefits of being in a larger vehicle when colliding
with a smaller vehicle (see Fig. 1, scenario 1). What is less recognized is that scen-
ario 1, with a large vehicle and a small vehicle colliding, is the least safe scenario in
terms of the combined safety of occupants of both vehicles.
Both SUV and car drivers agree that they are knowledgeable about vehicle safety
when responding to the Likert scale item ‘‘I am very knowledgeable about vehicle
safety’’ (Car M¼3.43, SD ¼0.78; SUV M¼3.63, SD ¼2.72; t[486] ¼0.373,
p>0.05).
3.4. Self–Other Comparisons
Drivers were asked to rate themselves and others on 11-point semantically
anchored items measuring safety (‘‘0 ¼not safe at all’’ through to ‘‘10 ¼very
safe’’) and consideration (‘‘0 ¼not considerate at all’’ through to ‘‘10 ¼very con-
siderate’’) (Table 4). Self–other comparisons using repeated measures t-tests found
that SUV and car drivers all rate themselves as safer (t[490] ¼24.704,
p<0.001) and more considerate (t[489] ¼26.343, p<0.001) than the average
driver. Independent samples t-tests reveal that SUV drivers believe they are safer
drivers when compared with car drivers (t[489] ¼2.193, p<0.05).
3.5. Prestige
The Likert scale items ‘‘most people would like a vehicle like mine,’’ ‘‘I drive an
expensive vehicle,’’ ‘‘when I drive my vehicle it makes me feel I’m doing well in
life,’’ and ‘‘my vehicle is a reflection of my lifestyle’’ form a 4-item scale of prestige,
TABLE 3. Continued
Vehicle size and safety items
Car SUV
Mean
MSDMSDdifference Significance
13 An SUV is the safest vehicle on
the road
2.15 0.92 2.47 0.88 0.32
14 I would not feel safe in a
smaller car
2.59 0.98 2.91 1.01 0.33
15 When all things are
considered, it is safer to
drive a larger motor vehicle
3.14 0.88 3.50 0.78 0.36
16 Taller vehicles increase safety
as they provide better
visibility for the driver
3.12 0.99 3.58 0.84 0.46
17 A smaller vehicle would limit
the activities I currently
use my vehicle for
2.83 1.20 3.73 1.13 0.90
p<0.05, p<0.01, p<0.001.
J. A. Thomas and D. Walton
268 International Journal of Sustainable Transportation Vol. 2, No. 4, 2008
with a Cronbach’s alpha of 0.71. When the 4 prestige scale items are aggregated,
there is a significant difference (t [473] ¼4.484, p<0.001) between car drivers
(M¼10.36, SD ¼2.79) and SUV drivers (M¼11.40, SD ¼2.27).
3.6. Utility
Reported frequency of traveling off-road and dropping children at school were
used to measure the utility of cars and SUVs. Analysis using a Mantel–Haenszel
common odds ratio found that SUV drivers report that they are 5.16 times more
likely than car drivers to use their vehicle for off-road trips, such as traveling on
unsealed gravel=dirt roads, beaches, or farmland (p<0.001). Table 5 shows the
regularity of off-road trips (such as trips on unsealed gravel=dirt roads, beaches,
or farmland) for car and SUV drivers. Drivers of SUVs in the sample are more
likely to have children, but are no more likely to drop their children at school com-
pared with the car drivers in the sample.
4. DISCUSSION
The findings of this study show that concern for personal collision protection is
an essential part of the decision to drive an SUV and is likely to be raised as an
argument to defend driving an SUV. Drivers of SUVs appear narrowly focused
on the concept that ‘‘bigger is better’’ in the context of vehicle safety with little
regard for the negative safety implications for the occupants of other, smaller
Table 4. Means and standard deviations for self-other comparisons of safety and
consideration for SUV and car drivers.
Car SUV
Self–other comparisons MSDMSD
Estimate how safe the AVERAGE driver is 5.49 1.59 5.47 1.66
Estimate how safe a driver YOU are 6.99 1.55 7.28 1.39
Estimate how considerate the AVERAGE
driver is to other drivers
5.30 1.72 5.03 1.65
Estimate how considerate YOU are to other drivers 7.11 1.53 7.17 1.47
Table 5. Reported regularity of off-road trips for car and SUV drivers.
Regularity of off-road trips Car (%) SUV (%)
Daily 0.0 1.8
Weekly 0.4 5.0
Fortnightly 0.0 7.2
Monthly 5.4 12.2
6 Monthly 6.6 23.5
Annually 15.4 16.7
Never 72.2 33.5
Vehicle Size and Driver Perceptions of Safety
International Journal of Sustainable Transportation Vol. 2, No. 4, 2008 269
vehicles. SUV drivers also have a general dislike of driving a small car, expressing
reasons of reduced safety, reduced utility, and general unhappiness.
The ‘‘bigger is safer’’ attitude makes SUV drivers more likely to believe in any
benefits relating to a larger vehicle, even if these benefits are illusory. For example,
SUV drivers are more likely to accept a safety advantage from the increased visi-
bility of a taller vehicle, even though a taller vehicle is likely to block the view of
other drivers (Rudin-Brown, 2004), have greater blind spots, have a higher center
of gravity, and be more prone to rollover and loss of control accidents (Kweon and
Kockelman, 2003; Wenzel and Ross, 2005). The acceptance of illusory benefits is
not due to an impaired knowledge of vehicle size and safety, as car drivers have
a similar knowledge when tested. Rather, it appears to be based on a less rational
attitude toward personal safety.
Approximately two thirds of drivers know that two small vehicles colliding is the
safest collision scenario. Despite having the same knowledge of naı
¨ve physics
regarding vehicle size and collisions, SUV drivers are less accepting of the overall
safety advantages of smaller vehicles when compared with car drivers. They are less
accepting of any reduction in visibility for drivers that are following large vehicles,
and they are less accepting of any reduction in injury if there were fewer large vehi-
cles on the road. SUV drivers appear to adopt an egocentric approach to safety
where their individual safety needs are met with higher importance than are the
safety needs of other road users.
Drivers seem to have an inflated perception of positive safety benefits, such that
personal gains in safety mitigate the reduction to overall safety. Eighty-five percent
of drivers recognize the personal occupant safety benefits of a larger mass vehicle
relative to a smaller mass vehicle in two-vehicle collision scenarios, but only 55%of
drivers recognize that this is the least safe collision scenario. ‘‘Hard hitting’’ driver
safety advertising campaigns showing graphic accidents and media releases report-
ing annual and holiday period fatalities raise the awareness of New Zealand drivers
to the dangers of driving on the road. This heightened awareness encourages the
concept that there are ‘‘dangerous drivers’’ on the road and may heighten our
need to protect ourselves (Walton and McKeown, 2001).
The self-enhancement bias, which is supported by the findings of this study,
shows that drivers believe that they are safer when driving when compared with
the ‘‘typical other driver.’’ Rather than making an active change to a driving
style they perceive to be superior, drivers can purchase passive safety with a vehicle
they believe is safe. Vehicle crash test information that focuses on driver fatality risk
also heightens self-protection rather than examining the overall likelihood that
anyone is injured or killed in a collision.
To shift the perception away from self-protection, Tay (2002) suggests that we
should promote ‘‘nonaggressive’’ vehicles. For example, a tax could be placed
on the ‘‘aggressivity’’ of a vehicle, where vehicles are taxed on the likelihood
that they will kill or injure someone in a collision (Tay, 2002). The key is to take
the focus away from personal protection and recognize the overall cost of a colli-
sion (Wenzel and Ross, 2005). There is also a need to dispel incorrect perceptions,
such as those brought about by ‘‘limit ads,’’ which reinforce the exaggerated
handling capabilities of SUVs (United States Department of Justice, 2003). It is
an unlikely coincidence that off-road utility, prestige, and safety are three key
J. A. Thomas and D. Walton
270 International Journal of Sustainable Transportation Vol. 2, No. 4, 2008
elements promoted by SUV advertising campaigns and are also three key factors
that explain SUV use in this study.
In addition to safety concerns, the added utility provided by SUVs influence
SUV use. According to an Australian insurance questionnaire, the primary reason
for purchasing a four-wheel-drive is ‘‘off-road exploring’’ (AAMI, 2004). The find-
ings of this research also show off-road functionality to be a key factor in driving an
SUV. Drivers of SUVs report that they are about five times more likely to drive on
unsealed roads, beaches, or farmland than are car drivers. However, one third of
SUV drivers never use their SUV off-road, increasing to two thirds if you take
into account infrequent (6-monthly and annual) trips.
SUV drivers purchase utility for infrequent trips and then make daily trips in
that same vehicle out of convenience rather than efficiency. Therefore, ‘‘anti-
SUV’’ claims that only a minority of SUV drivers use their vehicles off-road (e.g.,
Bradsher, 2004) may not have foundation, but the low frequency of off-road
trips could be viewed as problematic for a sustainable transport fleet. There is a
limitation to these findings, as they are found in an urban sample, and frequency
of off-road trips may be higher in rural locations.
SUV drivers are more likely to have children than are car drivers but are no
more likely to drop their children at school. If SUV drivers were driving a larger
vehicle to ‘‘defend the family,’’ particularly their vulnerable children, or to utilize
the additional carrying capacity of their vehicle, then they should also be more
likely than car drivers to drop their children to school. Parents may rationalize
their use of an SUV because they have children, but in reality other factors are
more likely to be motivating them.
SUV drivers have higher incomes and value the prestige of their vehicle more
highly than do other drivers when making a vehicle purchase decision. Much of
this motivation stems from the cost of the vehicle and the perception that cost
excludes other people that are envious of people that drive SUVs. While size
often implies value, this is not necessarily the case with vehicles; for example,
sports cars are often associated with lifestyle and prestige and expense. Therefore,
a smaller, expensive vehicle may still accommodate the same level of prestige with-
out the negative safety and emissions impacts of a larger vehicle.
5. CONCLUSIONS
The trend toward larger vehicles does not fit into the model of sustainable trans-
port. In contrast with smaller cars, SUVs use more resources to make and run and
have negative safety and environmental impacts of the vehicle fleet. The findings
of this study show that perceptions of large vehicle safety, off-road use, and prestige
all relate strongly to SUV use. The safety arguments raised by SUV drivers are not
based on a better understanding of collisions. SUV drivers appear to have a narrow,
egocentric perception that ‘‘bigger is safer,’’ with a focus on personal protection.
Transport policy concerning road safety should aim at reducing false perceptions
regarding larger vehicles, such as those promoted by ‘‘limit ads,’’ and switch the
focus from personal collision protection to overall protection, with a stronger
consideration for more vulnerable road users.
Vehicle Size and Driver Perceptions of Safety
International Journal of Sustainable Transportation Vol. 2, No. 4, 2008 271
ACKNOWLEDGMENTS
This research was conducted in collaboration with SHORE within a program of
public good research funded by the Foundation for Science, Research and Tech-
nology (OPSX0402), New Zealand. Thank you to Steve Lamb, Steve Murray, and
the reviewers for their contributions.
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