[Driver Attitude] [Older Drivers] [Licensing Older Drivers]
[Ergonomic Intro] [HF & Litigation] [HF Consulting]
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Last updated 17 July 1997
Erik C. B. Olsen, M.S.
Forty-nine thousand three hundred (49,300) people were killed in the
United States in motor-vehicle accidents in 1990 (1993 Almanac). Senior
drivers were only involved with approximately 12-14 percent of these
total fatalities (Klamm, 1985). However when driving exposure is
considered (Waller & Reinfurt,1973; States, 1985), drivers over 55 are
the second to the worst group-the 15 to 24 year olds.
As reported by Winter (1984), over 1.4 million licensed drivers in
the United States are 55 and over. By the year 2000 the projection is 28%
of the total amount of drivers and by 2050, 39%. Since Americans are
living longer and people are having less children, the baby boom of the
40's is becoming the senior boom of the 80's and 90's.
Finesilver (1969) studied accident statistics and concluded that
drivers over 65 have the lowest median accident involvement index of any
age group, but are more likely to have a fatal accident than any driver
from age 35 to 64. The increased amount of reported fatalities of older
drivers may be due partially to greater fragility and medical
complications - a 20 year old and a 60 year old's body will react
differently to the force of his or her body being thrown into a moving
vehicle. Waller (1986) points out that just as most persons age 60 or
older do not have sports injuries due to participation in strenuous sports,
their average crash risk is lower due to the trend that these drivers have
reduced driving amount, drive when traffic is less heavy, and avoid driving
after dark.
The literature indicates two major problems in dealing with using
accident rates, fatalities, and driving exposure as measures of driving
performance. In assessing and evaluating driving skills, whose poor
performance, may be an indication of more driving accidents, researchers
must carefully consider exactly what it is they are trying to test. One of
the main problems in addressing older driver issues is pointed out by
Cerrelli (1989). There is no unique source of data to address these issues;
An accurate understanding of the crash experience of older drivers and the
injury consequences of these crashes must use data from several sources
to make estimates.
The two problems have to do with data interpretation. As previously
mentioned, driving performance, in the form of reported fatalities, may
not accurately reflect older drivers' abilities. Depending on how one
interprets available data on miles driven, age, and fatalities, one may
show that more older drivers die, compared to other groups, per accident
(or mile driven) from injuries incurred during or after an accident. One
could conclude that older drivers are poorer drivers because they are
involved with more fatals. On the other hand, as pointed out by Evans
(1986), older drivers reduce their amount driven and drive at safer, less
busy times of the day resulting in a lower potential for an automobile
accident.
In later studies, Cerrelli (1989) and Evans (1991) both provide
information for and against the issue of older drivers being safer drivers.
Support of safe older drivers is evidenced by Evans (1991) suggestion that
drivers pose less of a threat to other road users due to their reduction in
driving. Cerrelli (1989) contrasts crashes of older drivers with the larger
crash involvement rate of the general population to show that older
drivers may become safer as they age. By looking at risk of crash
involvement based on vehicle miles of travel, Cerrelli (1989) and Evans
(1991) report increases of crashes for older drivers.
Setting interpretation differences aside, the overwhelming
conclusion is that more research on older drivers needs to be conducted.
This is based on the fact older drivers, ie., those age 65 and older, are
increasing both in number and in proportion at a faster rate than any other
segment of the licensed population (Waller, 1993). The issues of driver
mobility, safety and health, accidents, cognition, attention, chronological
age versus functional age, and highway design could all be addressed in a
comprehensive review. For this review, we continue with a look at one
foundation area of testing older drivers - reaction time, but first, let us
define what "older" is.
According to the United States government old is 65 years or older -
retirement age. Our movie theatres have "elderly rates" starting at a
particular age, ranging from 55 to 62 to 65. Virtually all commercial
pilots retire at or before the age of 60 (Hancock, Dewing, & Parasuraman,
1993). Classic driver researchers such as McKnight & McKnight (1993)
found significant age differences among subjects over age 50, while Ellis
& Hames (1975) refer to drivers over 65. Ranney & Pulling (1989) were
able to access local senior citizen activity centers to test a group of
older drivers between 74-83. Similarly, the Transportation Research
Board (1991) refers to drivers between 75-80 as "older-old." More
categorically, Waller (1991) refers to several groups such as young-old
(55-64), middle old (65-74), old old (75-84) and very old (85 and older).
Obviously, the "older drivers" category can be subjectively chosen, but a
review of the representative literature indicated that 65 age is usually
used. Age 65, as pointed out by Evans (1988), is often chosen because it it
the oldest convenient year contained in reports generated by agencies such
as the National Highway Traffic Safety Administration and the Nationwide
Personal Transportation Study of the U.S. Department of Transportation,
the U.S. Bureau of the Census, the Federal Highway Administration, and the
National Center for Health Statistics. Generally, earlier studies, such as
those done in the 1960-1970's use 50 or 55 as the lower limit for the
older drivers. Later studies have been using the age of 65, mostly, with a
recent emphasis of the "75+" group. This may be due to the trend, as
reported by Cerrelli (1989), as well as the Transportation Research Board
(1991), that this group of drivers is growing at an alarming rate, and that
little research has been conducted using this as a age range. (Perhaps, it's
time to raise our "senior" age, since people are living longer).
Why test older drivers? Reports show older drivers may have more
accidents due to slower reaction time (RT) decision time (cognitive), and
may be riskier drivers. Understanding older drivers and accurately testing
them will assist highway and safety engineers, physicians, psychologists,
physical trainers, law enforcement, as well as the general public. Since
we all drive and we all age, we must address this issue for our families,
friends, and our present and future selves.
The question of whether age correlates to RT is another classic
issue addressed in this review. Driver reaction time can be tested easily
as an indication of performance in a variety of ways. In an overview of 26
studies on simple RT and age, Birren, Woods, and Williams (1980) reported
that, on the average, there was a 20 percent difference in RT between
20-year olds and 60-year olds. Older drivers have trouble reacting quickly
in task-complex situations. These factors contribute to the slow
response reported among older drivers (AAA, 1988).
According to Schmidt (1988), RT is a measure of the time from the
arrival of a suddenly presented and unanticipated signal to the beginning
of the response to it. Movement time (MT) is the measure of time from the
initiation of the response to the completion of the movement. Total
response time is the summation of RT and MT (e.g., AAA, 1988). Total
response time (AAA, 1989) or brake reaction time (Schmidt, 1988), is the
time from the initiation of a stimulus to the time when one fully
depresses a brake pedal (AAA, 1989). In driving, stopping distance of a
vehicle is often referred to. This is broken down into "thinking distance"
and "braking distance," (Palatnick, 1974). Palatnick continues, stating
that thinking distance starts from the driver's decision to stop, until his
or her foot hits the brake pedal; he calls this RT. A certain amount of
time passes, and a certain distance is traveled without the brakes being
applied. Actual braking distance begins when the movement to the brake
pedal is completed and a continuous force is applied. After the brake is
hit, the braking distance takes up a certain amount of time as well.
Apparently Palatnick's version of RT differs, where he combines
Schmidt's RT and MT. The issue of braking time (time one pushes on the
brake) is not addressed separately by Palatnick but, according to AAA
(1988), this is part of MT.
RT can further be segmented into premotor RT and motor RT.
Premotor RT, which is not included in Palatnick's RT in that he refers to
one's decision to stop, and motor RT (Schmidt, 1988; Spirduso, 1980) have
been proposed, but are combined in most studies as simple RT, since EMG
recordings are difficult to implement in many situations.
Regardless, using simple physics, total stopping time can be
calculated by considering thinking and braking distance separately and
adding their calculated values together. We find that this amount of time
depends on the speed (and friction on the road) of the vehicle. Since most
car companies don't grant our universities and research institutes all of
our wishes, we cannot use actual vehicles to test subjects (in most
cases). It seems apparent that as one ages, one will take longer to react
to a stimulus. In driving, this can result in longer stopping times, which
may lead to more car accidents (For a more detailed explanation of RT,
driving, and braking consult, Baker, 1986 and Fricke, 1990. For more
details regarding RT and human performance consult Schmidt, 1988).
The slowing of response time (and reaction time) with age is well
documented (Salthouse, 1985). A study by Hodgkins (1962) concluded that
both RT and MT systematically slow as the age of subjects increased,
starting at age 30. People become slower with age; this may be attributed
to the slowing of neurological activities of the nervous system and/or to
the apparent fact that older people become more conservative and
cautious as they age and therefore more unwilling to make errors. Klein
(1991) reports that among various factors, response times may further
affect driver performance. Further, the results of Ranney and Pulling's
(1989) study indicate that for drivers over 74, slowing of RT has a strong
association with driving performance.
One practical implication of how slowing RT can affect driver
performance is by looking at intersection crashes, especially in reference
to older drivers who seem to have more difficulty in dealing with the
complexity of intersections (Waller, 1986). Zador et al, (1985) reports
that studies have shown that if the speed at which a traffic light changes
from green to red is slowed to 10 percent under recommended speed, one
fourth as many intersection crashes occur compared to intersections with
a 10 percent speedup over recommended times.
Other studies, e.g., Brown, Tickner, Simmonds, (1969); Stein and
Parseghian (1987); and Green, Williams, Serafin, Paelke (1991), suggest
that using a car phone while driving may affect RT and driver performance.
Specifically, Nilsson (1993) reported that the braking reaction times for
young subjects (under 60) were 2.19 seconds when talking on the phone
and 3.48 seconds for elderly subjects when talking on the phone. For the
older drivers, this is about 1.5 seconds longer than a normal reaction time
of 2 seconds for the elderly. Results such as these warrant serious
consideration. Aging and driving research must continue.
Other areas of study regarding aging and driving include issues of
visual requirements, age-related eye diseases, dementia, e.g., Alzheimer's
disease, intersection-signal engineering, divided attention, experience in
driving, medications and safety, mobility needs, and cognitive-motor
abilities, of the elderly driver (see Human Factors, Vol. 33 and 34 for a
complete review). Issues of concern also include physical fitness, weight
training and exercise, range of motion, flexibility, as well as testing
methods, e.g., simulators, laboratory testing, and field testing, reporting
results, e.g., self, government, mandatory, and DMV, and highway and
vehicle design, including alternate transportation.
An overwhelming number of subjects, as demonstrated above, is related to driving and aging. As demonstrated by this representative literature review these areas of study are becoming increasingly important. In this review statistics and data interpretation, reaction time and driver performance, as well as a listing of related subjects has been represented in regards to aging and driving.
AAA Foundation of Traffic Safety (1989). Physical fitness and the aging
driver: phase II. (Conducted by West Virginia University).
Washington, D.C.
Baker, J. Stannard and Fricke, Lynn B. (1986). The Traffic-Accident
Investigation Manual. Illinois: Northwestern University Traffic
Institute.
Birren, J. E., Woods, A.M., and Williams, M.V. (1980). Behavioral slowing
with age: Causes, organization, and consequences. In Aging in the
1980's, (Poon, ed.). Washington, D.C.: American Psychological
Association.
Brown, I.D., Tickner, A.H., Simmonds, D.C.V. (1969). Interference between
concurrent tasks of driving and telephoning. Journal of Applied
Psychology, 53(5), 419-424.
CHP (California Highway Patrol). (1990). Annual Report. Sacramento:
State of California.
Cerrelli, E. (1989). Older drivers, the age factor in traffic safety (Report
No. DOT HS 807 402). Washington, DC: National Highway Traffic
Safety Administration.
Evans, Leonard. (1986), The effectiveness of safety belts in preventing
fatalities. Accident Analysis and Prevention,18, 229-241.
Evans, Leonard. (1991). Traffic Safety and the Driver. New York: Van
Nostrand Reinhold.
Finesilver, S.G. (1969). The Older Driver-A Statistical Evaluation of
Licensing and Accident Involvement in 30 States and the District of
Columbia. Denver: University of Denver College of Law. January.
Fricke, Lynn B. (1990). Traffic Accident Reconstruction. Illinois:
Northwestern University Traffic Institute.
Green, P., Williams, M., Serafin, C., and Paelke, G. (1991). Human factors
research on future automotive instrumentation: A progress report.
Proceedings of the Human Factors Society 35th Annual Meeting -
1991. 1120-1124.
Hancock, P.A., Dewing W.L., and Parasuraman, Raja. The human factors of
intelligent travel systems. Ergonomics in Design, 12-39. April
1993.
Klamm, E.R. (1985). Auto insurance: needs and problems of drivers 55 and
over. In Needs and Problems of Older Drivers: Survey Results and
Recommendations, J. W. Malfetti, ed. Falls Church: AAA Foundation
for Traffic Safety.
Kline, D.W., and Fuchs, P. (1993). The visibility of symbolic highway signs
can be increased among drivers of all ages. Human Factors, 35(1),
25-34.
Kline, Ronald. (1991). Age-related disease, visual impairment, and driving
in the elderly. Human Factors, 33(5), 521-525.
McKnight, J.A., and McKnight, A.S. (1993). The effect of cellular phone use upon driver attention. Accident Analysis & Prevention,
25(3) 250-365.
Nilsson, L. (1993). Behavioral research in an advanced driving simulator -
experiences of the VTI system. Proceedings of the Human Factors
Society 37th Annual Meeting - 1993. 612-616.
Salthouse, T.A. (1985). A Theory of Cognitive Aging. Amsterdam: North
Holland.
Schmidt, R.A. (1988). Motor Control and Learning: A Behavior Emphasis
(2nd ed.). Champaign, IL: Human Kinetics Publishers, Inc.
Spirduso, W.W. (1980). Physical fitness, aging, and psychomotor speed: A
review. Journal of Gerontology, 35, 850-865.
States, J.D. (1985). Musculoskeletal system impairment related to safety
and comfort of drivers over 55. In Needs and Problems of Older
Drivers: Survey Results and Recommendations, J.W. Malfetti, ed.
Falls Church: AAA Foundation for Traffic Safety.
Transportation Research Board (1991). Older driver priority research and
development needs identified by TRB task force. (conference
summary). December 1991.
Waller, J.A. (1986). The older driver: Can technology decrease the risks?
Generations, Fall 1986.
Waller, P.F., and Reinfurt, D.W. (1973). The Who and When of Accident
Risk: Can Driver License Programs Provide Countermeasures? Chapel
Hill: University of North Carolina, Highway Safety Research Center. June
1973.
Winter, D.J. (1984). Needs and problems of older drivers and pedestrians:
An exploratory study with teaching/learning implications.
Educational Gerontology, 10, 135-146.
Zador, P. et al. (1985). The effect of signal timing on traffic flow and
crashes at signalized intersections. Transportation Research
Review, (Report No. 1010), 1-8. 12/9/93
After-thoughts
Self reports: Planek and Fowler (1971) used a questionnaire covering
biographical, driving experience and opinion data which was distributed to
groups of drivers 55 and older.
Kline & Fuchs (1993): The Transportation Research Board reported that
elderly drivers constitute the fastest growing segment of the driving
population.
Aging is accompanied by slowing in information processing (e.g.,
Birren, Woods, and Williams, 1980; Salthouse, 1982, 1985). Neuronal
noise (Crossman and Szafran, 1956, Layton, 1975, Welford 1958, 1965,
1981) causes cumulative loss of information in consecutive processing
steps, resulting in progressive slowing in successive processing steps
(Myerson, Hale, Wagstaff, Poon and Smith,1990). Known as the
slowing-complexity hypothesis, it may be possible that increased RT is a
result of progressive slowing in succeeding processing steps which
causes performance differences between age groups to increase
disproportionally with task complexity. This work has to do with dual
tasks, which one might be able to be apply to a driving situation, where RT
is measured. Driving, is more than a dual task, though; Others (e.g.,
McDowd and Craik, 1988, Salthouse, et al., 1984) suggest that these
age-related performance differences may be attributable to the solely the
complexity of the task.
Attempts use HP to predict accidents
As one gets older, it is believed (Schmidt, 1988), that humans increase
their capacities for processing information. Past the age of 25, though, a
progressive decline occurs in motor behavior.
Both research and self-reports conclude that older drivers visual
difficulties. This may compound the problem of attention of the older
drivers. One may need larger print, brighter signs, more lighting, etc., to
get the attention of an older driver.
Human performance as predictors
Kline and Fuchs (1993) demonstrated that, at least in a laboratory setting,
improved symbolic signs (by 50%) and assisted drivers of all ages.
Visibility was somewhat more greatly improved for elderly observers
than for young or middle-aged ones. Research such as this relies on the
fact that older drivers have poorer vision, which may result in less
attention capabilities (it takes more to get their attention).
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