Research Notes-Spring 1998
Revised Teen & Senior Facts Report Confirms Previous Trends
by Debbie McKenzie & Raymond Peck
How does driving record vary as a function of age? This frequently asked question is addressed in the report Teen and Senior Drivers (fourth edition) (Aizenberg & McKenzie, 1997), done by a cooperative agreement between the Beverly Foundation and DMV's Research and Development Branch. The authors concluded that the answer depends a lot on whether one compares drivers in terms of collision rates per driver or rates per 100,000 miles driven.
Figure 1 & 2 shows annual per driver collision rates by age and sex for 1995. Figure 1 presents fatal/injury accident rates while Figure 2 is limited to at-fault fatal accidents. Analysis of these data permits the following conclusions:
- For each sex, drivers aged 16-19 have the highest collision rates.
- Regardless of age, men consistently exhibit higher collision rates.
- Collision rates for both sexes decline until about age 70 and then increase.
- The increase in at-fault fatal accidents becomes particularly dramatic at age 80+.
Since the amount of driving is known
to vary as a function of age and sex, the rates shown
in Figures 1 & 2 are influenced by these differences.
All things being equal, high-mileage drivers will tend
to be involved in more collisions than will low-mileage
drivers. In order to derive a measure that adjusts,
at least partially, for these differences in risk exposure,
the authors of the 1993 Teen and Senior report obtained
annual mileage data by age and sex for California drivers
from the 1990 Nationwide Personal Transportation
Survey. These data were used to created the "mileage-adjusted"
rates shown in Figure 3. It is readily apparent that
the mileage-adjusted data provide a different picture.
We find that for collisions, the mileage-adjusted rates
show both young and old drivers to be overinvolved,
with the rates becoming highly accelerated at age 80
and above. Although the mileage-adjusted rates are not
without limitations, many authorities regard them as
being better indicators of collision avoidance skill
than unadjusted rates.
Several conclusions can be drawn from Figure 3.
- In agreement with other studies, the youngest and oldest drivers have the highest mileage-adjusted collision rates.
- The superior per driver collision rate of older drivers and women is largely due to their driving fewer miles.
- Driving skill, in terms of collision avoidance, declines at advanced age. However, the upswing at age 80 exaggerates the decline for two reasons. First, drivers of advanced age are more vulnerable to injury and fatality, which would tend to increase their incidence of reported collisions. Second, older persons driving fewer miles are more likely to be driving in city and other non freeway traffic, where the risk of collisions per mile is higher.
Three new sections in the Teen and Senior report address driver movement preceding collision, type of collision, and time of collision. Among the findings reported were the following:
- Teens in crashes are more likely to have driven off the road than any other age group.
- Senior drivers are significantly more likely than teens and all other age groups to be turning left before a crash, especially at intersections.
- Broadside impacts and hit objects are the most prevalent collision types in fatal accidents for all age groups.
- For teen fatal accidents, most common collision type is hitting an object while for seniors it is a broadside impact. The incidence of broadside collisions in fatal accidents increases notably at age 70+.
- The most prevalent time period for fatal accidents involving older drivers is between noon and 6 p.m. In contrast, more fatal accidents involving teens occur between 6 p.m. and midnight than any other time period. These trends reflect the combined influence of temporal exposure (when people drive), type of driving, and alcohol.
Many studies have attributed the overinvolvement in traffic collisions of young drivers to inexperience, alcohol/drug consumption, poorer hazard perception skill and attitudinal factors such as increased risk-taking propensity. In an attempt to mitigate the effect of these factors, some jurisdictions have implemented countermeasures to improve the driving practices and attitudes of young novice drivers.
California has implemented a graduated licensing program for young drivers. Sixteen and 17-year-olds licensed after July 1, 1998 face new restrictions. For the first year of licensure, they will not be able to drive between midnight and 5 a.m., unless accompanied by a licensed driver 25 years or older. Also, for the first 6 months they will not be able to transport other teenagers. A number of prior studies indicate that graduated licensing reduces accidents.
Although many elderly drivers have deficiencies that impair their driving, in general they are able to effectively limit their collision risk by driving more slowly and cautiously, and by limiting the amount and conditions of their driving. Nevertheless, these deficiencies, without adequate compensation, do increase their collision liability. This has led to a variety of studies and proposed countermeasures. For example, Malfetti and Winter (1990) proposed guidelines for a graded license for selected elderly drivers that would be similar to a restricted license, and would be adapted to the driver's mode of living, driving needs, and ability. The graded license would allow impaired elders to operate a motor vehicle only under conditions that would not exceed their ability.
A variety of approaches, including the above, are currently being considered, both nationally and in California, in order to reduce collisions involving older drivers without unduly compromising mobility. As noted in Teen and Senior Drivers, the recent nationwide interest in the elderly driver as a driver licensing problem has been stimulated largely by demographic trends showing substantial increases in the percentage of drivers aged 70 and above—a trend that is projected to continue to the year 2025. As a result, the proportion of collisions involving older drivers is also increasing. Countermeasures which effectively target elderly drivers' safety and mobility problems are needed to minimize the impact of this trend. The proportion and number of traffic casualties involving teenagers is also projected to increase in coming years due to similar demographic trends.
To order a copy of the report Teen and Senior Drivers write to the DMV, Research and Development Branch at 2415 1st Avenue, Mail Station F-126, Sacramento, CA 95818, Fax No. (916) 657-8589, or by e-mail: dluong@dmv.ca.gov