Addressing the Safety Issues Related to Younger and Older Drivers

&nbspChapter 1

Issues Related to
Younger and Older Drivers

The National Highway Traffic Safety Administration (NHTSA) has had a long-standing interest in improving the safety of both younger and older drivers, and in recent years has revitalized its interest in improving the safety of these groups.

NHTSA's Research Approach

NHTSA's approach to dealing with the problems of younger and older drivers proceeds on two fronts. First, each of these age groups is addressed in dedicated research projects that focus on physical and behavioral problems or practices. Second, younger and older drivers are treated as part of the continuum of the overall driver population in research that focuses on specific safety issues. The Agency's research and rulemaking activities focus on underlying traits responsible for the crash experience, not just using age per se as a discriminating variable.

NHTSA's research efforts on behalf of younger and older drivers may also be characterized by the ultimate goals of those efforts. The Agency conducts behavioral research to improve safe driving actions through such avenues as increasing knowledge and changing attitudes. It also conducts biomechanics and human-factors research to improve safety performance of vehicles through increased crashworthiness and improved crash-avoidance design features. Since vehicle improvements generally benefit occupants of all ages, behavioral research tends to be more focused on specific age groups than vehicle-oriented research.

The Agency's behavioral research findings are incorporated into model safety programs and disseminated through published guidelines or reports of demonstration programs and program evaluations. States and communities are encouraged to adopt these model programs and implement them through their own legislative or program actions. The findings of the vehicle-oriented research are implemented through Agency rulemaking actions, which require vehicle manufacturers to comply.

Congressional Direction

This report on NHTSA's research agenda for addressing the safety issues of younger and older drivers was requested by the Committee on Appropriations of the U.S. Senate in Senate Report 102-148, which contained the following language:

The Transportation Research Board report entitled "Safety Research for a Changing Highway Environment" carefully documents the challenge to highway safety posed by both the older and younger populations. As the report notes, the high involvement rate of older drivers in crashes (on a mileage-driven basis) is second only to those of drivers under the age of 25. Although NHTSA has important programs focused on each of these populations, the Committee seeks to enhance these efforts. Consequently, the Committee requests that NHTSA submit a report detailing its research agenda on topics specifically addressing the unique safety issues related to the older and younger driver.

NHTSA Planning Documents

NHTSA has long been aware of the special needs of younger and older drivers. Accordingly, the Agency developed safety plans addressing each of these special populations some time ago. As information accrues and needs change, these plans are updated and revised. The request for this report came at a time when the Agency is extensively revising each of these plans. This section briefly summarizes the existing planning documents.

Young Adult Highway Safety Plan NHTSA's existing plan for road users aged 15 through 24 describes Agency program and research activities that address the highway safety issues prevalent among young drivers. This plan was first published in 1990.

The purpose of the NHTSA Young Adult Highway Safety Plan was to create an organized and focused approach to the population most at risk on our nation's highways: the driver under the age of 25. The Plan represented an integrated multi-disciplinary approach to a complicated traffic safety problem.

The young adult program was built upon a model initially developed as part of the Agency's anti-drunk-driving program. This model addressed the young adult highway safety problem in the areas of enforcement, adjudication, supervision, legislation, licensing, school-based programs, school-based extra-curricular programs, community based programs, and work-place based programs. These approaches were directed at the following priority areas: alcohol and other drugs, occupant protection, driver licensing, and motorcycles.

The output from this approach resulted in a presentation of (1) programs focused on a single issue; (2) comprehensive programs focused on two or more issues; and (3) research and development activities. This research effort is intended to identify attitudes and behaviors characteristic of young adults to aid us in developing increasingly effective strategies for dealing with this population segment.

Many of the long-term research activities described in the Plan have been completed or have provided sufficient new information in the area of problem identification. Some projects described have been completed and new ones have been initiated. The Agency is currently revising this Plan to reflect accumulated progress and to accommodate the findings of completed activities. The revision will be completed during Fiscal Year 1993.

Traffic Safety Plan for Older Persons NHTSA's Traffic Safety Plan for Older Persons addresses drivers, vehicle occupants, and pedestrians. The Agency developed the Plan in 1988 in response to recommendations in the Transportation Research Board's (TRB) Special Report #218, Transportation in an Aging Society. The Plan was developed to provide a comprehensive, coordinated program for improving the safety of older persons, while achieving a balance between safety and mobility.

NHTSA's Plan responded to the TRB report's recommendations and provided details of other work deemed necessary to improve the safety of older persons. It called for conducting research in problem identification, occupant protection, driver licensing, pedestrian safety, consumer information and vehicle safety.

NHTSA has completed many of the activities described in the Plan and conducted additional problem-definition activities, including co-sponsoring an international conference on research needs of older drivers. The results of these activities produced new knowledge about older-driver problems that suggested improved ways of addressing both safety and mobility issues. This research has significantly refined the older person traffic safety issues and provided information to older person groups in both driving and pedestrian areas.

The Plan was designed to encourage close working relationships with other Federal agencies, the States, and additional concerned groups. While implementing the Plan, NHTSA has established lines of coordination across both State and Federal government agencies and private-sector groups. These connections have stimulated and guided research activities by other organizations well beyond the level that this Agency would be able to support.

The 1988 Plan for older persons is undergoing a major revision, and is scheduled to be completed during Fiscal Year 1993.

Characteristics of Younger and Older Drivers

The foundation of all traffic safety research is a thorough analysis of relevant data to identify problem areas and define populations needing special attention. The appropriateness and effectiveness of countermeasure development rests on this foundation. This section summarizes the Agency's findings regarding the level of crash involvement of younger and older drivers, and characteristics of the crashes that differentiate between the two age groups. Additionally, this section presents information on differences in performance abilities that distinguish the two groups.

Involvement in Crashes An evaluation of the relative magnitudes of the crash problems contributed by younger and older drivers indicates that younger-driver problems vastly exceed older-driver problems. Figures 1 through 7 summarize crash data from NHTSA and Federal Highway Administration (FHWA) sources.

Figures 1 and 2 show, respectively, the number of drivers and the distance that they travel by age group. The similar shape of these two curves shows that the mileage traveled by each age group is closely related to the number of drivers in the age group. In 1990 there were slightly more than 26 million licensed drivers, ages 15 through 24, and about 22 million licensed drivers, 65 years of age or older. Although younger drivers only slightly outnumber older drivers (16 percent to 13 percent of the population of licensed drivers, respectively), the younger group drove more than twice as many miles as the older group.

Figure 1. Number of Licensed Drivers by Age Group

Figure 2. Total Miles of Travel by Age Group

Figures 3 and 4 show, respectively, the number of drivers in reported crashes and the number of fatalities resulting from those crashes. The shapes of these two curves are also nearly parallel, showing that the relationship between crashes and fatalities is roughly the same for all but the older drivers. Younger drivers were involved in four times as many reported crashes as the older group. They also were involved in three times as many fatal crashes as older drivers. Compared with older drivers, more than twice as many younger drivers died.

Figure 3. Number of Drivers in Reported Crashes by Age Group

Figure 4. Number of Driver Fatalities by Age Group

Figure 5 shows that after the number of crashes is adjusted for the number of licensed drivers in the age group, younger drivers are considerably more likely to be involved in a crash than are older drivers. In fact, the per-person crash involvement rate decreases as age increases until drivers reach 85 or more years of age. Even this age group has a per-driver crash rate lower than drivers younger than 50 years of age.

Figure 5. Crash Involvement Rate per Thousand Licensed Drivers by Age Group

While the per-person rates reflect a smaller proportion of older drivers involved in crashes than younger drivers, adjusting the number of crashes by the total mileage traveled by members of each age group reveals a different pattern. Figure 6 shows the number of crashes per 100-million miles traveled. This curve indicates that the highest per-mile crash rates occur among the youngest and the oldest age groups. This demonstrates that an "average mile" driven by a member of one of these two groups is more dangerous than an "average mile" driven by a member of an intermediate age group.

However, since drivers at either end of the age range drive far fewer miles than those in between, researchers have questioned the equality of those "average miles" across age groups. Unlike younger and older drivers, drivers in the intermediate age groups travel a sizeable proportion of their annual miles on expressways and other inter-city roadways. These types of roads typically offer fewer hazards than do roads in urban areas. Most of the miles driven by younger and older drivers involve congested areas and heavy concentrations of intersections that offer relatively more opportunities for conflict with pedestrians and other vehicles.

Figure 6. Crash Involvement Rate per 100 Million Miles VMT by Age Group

Fatality rates reveal that older drivers are at increased risk of dying, whether the rate is based on the number of licensed drivers (shown in Figure 7) or on the total vehicle miles traveled (shown in Figure 8).

Figure 7. Fatality Rate per Thousand Licensed Drivers by Age Group

Figure 8. Fatality Rate per 100 Million Vehicle Miles Traveled by Age Group

If drivers of any age were equally likely to die from crash injuries, then the shape of Figure 7 should be the same as Figure 5. This condition appears to hold for drivers below the age of 60 or so. However, drivers older than 60 years of age show increasing fatality rates, indicating that older drivers suffer more serious injuries in crashes than do younger drivers. This increase in driver fragility with age is shown more clearly by plotting the rate of fatalities per crash by age, as in Figure 9.

On a per-mile basis, older drivers have a greater fatality rate than other-aged drivers. But by any other measure, younger drivers outnumber, out-travel, out-crash, and out-die older drivers. However, once they are in a crash, older drivers are more than three times as likely to die than are younger drivers.

Figure 9. Driver Fragility by Age Group

Characteristics of Crashes By looking at the relative proportions of involvement in different types of crashes, it is possible to gain some understanding of the differences and similarities between age groups, independent of the absolute levels of involvement. Analysis of police crash reports contained in NHTSA's 5-State Crash Avoidance Research Data File (CARDFILE) reveals some striking differences and some surprising similarities between the crash patterns of younger and older drivers.

Time of Day Figure 10 shows the hour-by-hour pattern of crashes by drivers of different ages. The younger-driver crash pattern does not differ much from that of drivers between the ages of 25 and 64, showing the majority of crashes occurring between 7:00 a.m. and 8:00 p.m., with a small peak during the hours of morning rush hour and a large peak during evening rush hour. After 8:00 p.m., the number of crashes declines slowly to a minimum around 4:00 a.m. (for 25 to 64 year-old drivers) or 5:00 a.m. (for 15-24 year-old drivers). Older drivers, on the other hand, have few crashes between 8:00 p.m. and 7:00 a.m. The crash patterns of older drivers do not show rush-hour peaks, but rather a slow increase in number from 7:00 a.m. to about 11:00 a.m., remaining flat until about 4:00 p.m., and slowly decreasing until around 8:00 p.m.

Figure 10. Number of Crashes by Time of Crash and Age Group

Light Conditions The relationship between crashes and lighting parallel the patterns of crashes by time of day. Well over half of all crashes occur during daylight hours. However, the relative proportions of daylight and dark crashes vary with age, as shown in Figure 11. The 15 to 24 age group has one in three (33 percent) of their crashes after dark. Drivers between 25 and 64 have one in four (25 percent) crashes after dark. Drivers between 65 and 74 have one in eight (12.5 percent) of their crashes after dark, and the oldest group (75 years of age or older) has one in twelve (8.3 percent) crashes after dark. These results follow the reported driving habits of older drivers: they tend to drive less and less after dark as they get older. Many do not drive after dark at all.

Figure 11. Percent of Crashes by Light Conditions and Age Group

Crash Severity Remarkably, the distribution of crash severity is almost identical across age groups, as shown in Figure 12. About 60 percent of all crashes involve property damage only; 22 to 23 percent involve possible injury; 12 percent non-incapacitating injury; 5 percent incapacitating injury; and fewer than one percent of crashes involve fatal injury. Among the fatal-injury crashes, the level of involvement increases with age, with 0.6 percent for drivers 15 to 64; 0.7 percent for drivers 65 to 74; and 0.9 percent for drivers 75 and older.

Figure 12. Percent of Crashes by Severity Level and Age Group

Number of Vehicles Involved The majority of crashes involve two vehicles, regardless of drivers' age, as shown in Figure 13. Among younger drivers, two-vehicle crashes account for 68 percent of all crashes, compared with 71 percent of drivers 25 to 64, and 80 percent of drivers 65 and older. The percentage-point differences between age groups on two-vehicle crashes are largely made up in single-vehicle crashes. Proportions of single-vehicle crashes from the youngest to the oldest are 21 percent, 16 percent, and 10 percent, respectively.

Figure 13. Percent of Crashes by Number of Involved Vehicles and Age Group

Relationship to Intersection Most crashes for all age groups occur at intersections, although the proportions are somewhat different for the different groups, as shown in Figure 14. About 50 percent of crashes of the youngest and middle groups occur at intersections, whereas about 60 percent of older drivers' crashes occur at intersections. Younger drivers show a greater tendency than other age groups to be involved in non-intersection crashes, with 15-24 age group showing 43 percent, the 25-64 group showing 41 percent, and the 65-74 group showing 31 percent.

Figure 14. Percent of Crashes by Relationship to Intersection and Age Group

Pre-crash Maneuver More than half of the crashes of all age groups involve the vehicle going straight just prior to the crash, accounting for 59 percent of the youngest group's crashes, 57 percent of the middle group's crashes, and 53 percent of the oldest group's crashes. These proportions are shown in Figure 15. The most striking difference between the groups is in the proportion of crashes involving left turning. While 11 percent of younger drivers' crashes involved left-turning, 17 percent of older drivers' crashes involved left-turning. Within the older driver group, the oldest drivers show the greatest proportion of crashes in this category, involving 16 percent of 65-74 year-old drivers' crashes and 21 percent of the crashes of drivers 75 years old or more.

Figure 15. Percent of Crashes by Vehicle Maneuver and Age Group

Driver Error Excessive speed is the primary error in 15 percent of younger-driver crashes, but only in about 5 percent of older-driver crashes, as shown in Figure 16. Right-of-way violations are the primary error in 18 percent of older-driver crashes, but only in about 9 percent of younger-driver crashes. Older drivers also make more errors at signed or signalized intersections than do younger drivers: 14 percent and 9 percent respectively. Driver inattention, which includes falling asleep at the wheel, was about equally likely among younger and older drivers, accounting for slightly more than 5 percent of crashes in each group.

Figure 16. Percent of Crashes by Driver Error and Age Group

Alcohol Involvement Blood Alcohol Concentrations (BAC) at or above .10 percent are detected in about 6.5 percent of crash-involved younger drivers. Drivers between 25 and 64 years of age also show BACs at or above .10 percent in 6.5 percent of their crashes. Older drivers, however, show BACs at or above .10 percent in less than 2 percent of their crashes. These relationships are shown in Figure 17.

Alcohol plays a much larger role in fatal crashes. One out of 10 fatal crashes in 1990 involved drivers or pedestrians with BACs between .01 and .09 percent, while 4 of 10 involved drivers or pedestrians with BACs at or above .10 percent. Twenty-seven percent of young drivers in fatal crashes had BACs at or above .10 percent, compared with 26 percent of drivers between 25 and 64, and 6 percent of drivers 65 years old or older.

Figure 17. Percent of Crashes by Driver Use of Alcohol or Drugs and Age Group

Sources of Risk for Younger Drivers: Problem Behaviors The primary problems of drivers between 15 and 25 years of age appear to be related to lack of experience, immature judgment, and risk taking. Younger drivers have limited life experience to rely upon in developing responses to the driving environment.

Some researchers contend that younger persons, especially in the teen years, have a sense of immortality and invulnerability to danger that carries over into their driving behaviors. Younger drivers tend to believe that crashes only happen to others. Some younger individuals also tend to display other characteristics that foster unsafe driving. Younger drivers perceive risk differently than older drivers. A NHTSA study found that younger drivers rated speeding as less dangerous than did their more experienced counterparts. There also was evidence that young drivers saw themselves as more skillful than their peers, and that young drivers' increased familiarity with a driving location reduced their perception of danger in that situation. This was not found for more experienced drivers. The findings suggested that, relative to drivers over 25 years of age, young drivers associated lower risks with certain driving acts and underestimated their personal risk of being involved in a crash. .

Personality factors, particularly among males, may also contribute to the young driver problem. The literature includes references to over-expression of impulsiveness, daredevil driving, anger in traffic situations, and driving to let off steam after arguments. There also are weak but consistent correlations between various "anti-social" personality traits (more common among the young than other age groups) and higher crash rates.

Sources of Risk for Older Drivers: Declining Capabilities The research literature confirms conventional knowledge about the effects of aging on cognitive, perceptual, and motor abilities.

Age-related changes in vision make it more difficult for older adults to accommodate to darkness, recognize objects under low lighting conditions, recover from glare, and search their environment. Virtually all behavior slows with age, with performance decrements being more pronounced as task complexity and cognitive demands increase. Making decisions becomes more difficult, as does changing a course of action once a commitment has been made. Memory deteriorates with age, although the decline in healthy adults is not as great as previously believed. Short-term memory, in particular, is affected by aging. While few studies linked cognitive declines specifically to driving abilities, it is clear that these kinds of changes in abilities could pose problems for drivers who experience them.

Experience and judgment are qualities that can contribute to compensating for slowed responses and sensory deficiencies. Evidence shows that most older drivers are aware of their changing abilities and adapt accordingly: making shorter trips totaling far fewer miles, and driving substantially less at night, in heavy traffic, and in bad weather. These self-regulated changes in exposure to risk largely account for the differences in crash characteristics between younger and older drivers.

Driving problems increase with the seriousness of certain medical conditions. To the extent that older individuals are aware of their conditions, they tend to limit their driving appropriately. But, if they are victims of conditions of which they cannot be aware, they appear not to limit their driving and are consequently exposed to greater crash risk. Cognitive disorders, such as Alzheimer's Disease and difficulties performing tasks that require processing of several sources of information are among the most serious of these latter conditions.

Older drivers' safety problems are exacerbated by increasing frailty. Drivers 75 years old or older are three times as likely to die in a crash than are 20 year old drivers.

&nbspGo to Chapter 2

		NHTSA has long been aware of the special needs of younger and older drivers. Accordingly, the Agency developed safety plans addressing each of these special populations some time ago. As information accrues and needs change, these plans are updated and revised. The request for this report came at a time when the Agency is extensively revising each of these plans. This section briefly summarizes the existing planning documents.
Young Adult Highway Safety Plan		NHTSA's existing plan for road users aged 15 through 24 describes Agency program and research activities that address the highway safety issues prevalent among young drivers. This plan was first published in 1990. The purpose of the NHTSA Young Adult Highway Safety Plan was to create an organized and focused approach to the population most at risk on our nation's highways: the driver under the age of 25. The Plan represented an integrated multi-disciplinary approach to a complicated traffic safety problem. The young adult program was built upon a model initially developed as part of the Agency's anti-drunk-driving program. This model addressed the young adult highway safety problem in the areas of enforcement, adjudication, supervision, legislation, licensing, school-based programs, school-based extra-curricular programs, community based programs, and work-place based programs. These approaches were directed at the following priority areas: alcohol and other drugs, occupant protection, driver licensing, and motorcycles. The output from this approach resulted in a presentation of (1) programs focused on a single issue; (2) comprehensive programs focused on two or more issues; and (3) research and development activities. This research effort is intended to identify attitudes and behaviors characteristic of young adults to aid us in developing increasingly effective strategies for dealing with this population segment. Many of the long-term research activities described in the Plan have been completed or have provided sufficient new information in the area of problem identification. Some projects described have been completed and new ones have been initiated. The Agency is currently revising this Plan to reflect accumulated progress and to accommodate the findings of completed activities. The revision will be completed during Fiscal Year 1993.
Traffic Safety Plan for Older Persons		NHTSA's Traffic Safety Plan for Older Persons addresses drivers, vehicle occupants, and pedestrians. The Agency developed the Plan in 1988 in response to recommendations in the Transportation Research Board's (TRB) Special Report #218, Transportation in an Aging Society. The Plan was developed to provide a comprehensive, coordinated program for improving the safety of older persons, while achieving a balance between safety and mobility. NHTSA's Plan responded to the TRB report's recommendations and provided details of other work deemed necessary to improve the safety of older persons. It called for conducting research in problem identification, occupant protection, driver licensing, pedestrian safety, consumer information and vehicle safety. NHTSA has completed many of the activities described in the Plan and conducted additional problem-definition activities, including co-sponsoring an international conference on research needs of older drivers. The results of these activities produced new knowledge about older-driver problems that suggested improved ways of addressing both safety and mobility issues. This research has significantly refined the older person traffic safety issues and provided information to older person groups in both driving and pedestrian areas. The Plan was designed to encourage close working relationships with other Federal agencies, the States, and additional concerned groups. While implementing the Plan, NHTSA has established lines of coordination across both State and Federal government agencies and private-sector groups. These connections have stimulated and guided research activities by other organizations well beyond the level that this Agency would be able to support. The 1988 Plan for older persons is undergoing a major revision, and is scheduled to be completed during Fiscal Year 1993.

		The foundation of all traffic safety research is a thorough analysis of relevant data to identify problem areas and define populations needing special attention. The appropriateness and effectiveness of countermeasure development rests on this foundation. This section summarizes the Agency's findings regarding the level of crash involvement of younger and older drivers, and characteristics of the crashes that differentiate between the two age groups. Additionally, this section presents information on differences in performance abilities that distinguish the two groups.
Involvement in Crashes		An evaluation of the relative magnitudes of the crash problems contributed by younger and older drivers indicates that younger-driver problems vastly exceed older-driver problems. Figures 1 through 7 summarize crash data from NHTSA and Federal Highway Administration (FHWA) sources. Figures 1 and 2 show, respectively, the number of drivers and the distance that they travel by age group. The similar shape of these two curves shows that the mileage traveled by each age group is closely related to the number of drivers in the age group. In 1990 there were slightly more than 26 million licensed drivers, ages 15 through 24, and about 22 million licensed drivers, 65 years of age or older. Although younger drivers only slightly outnumber older drivers (16 percent to 13 percent of the population of licensed drivers, respectively), the younger group drove more than twice as many miles as the older group.
Figure 1. Number of Licensed Drivers by Age Group
Figure 2. Total Miles of Travel by Age Group
		Figures 3 and 4 show, respectively, the number of drivers in reported crashes and the number of fatalities resulting from those crashes. The shapes of these two curves are also nearly parallel, showing that the relationship between crashes and fatalities is roughly the same for all but the older drivers. Younger drivers were involved in four times as many reported crashes as the older group. They also were involved in three times as many fatal crashes as older drivers. Compared with older drivers, more than twice as many younger drivers died.
Figure 3. Number of Drivers in Reported Crashes by Age Group
Figure 4. Number of Driver Fatalities by Age Group
		Figure 5 shows that after the number of crashes is adjusted for the number of licensed drivers in the age group, younger drivers are considerably more likely to be involved in a crash than are older drivers. In fact, the per-person crash involvement rate decreases as age increases until drivers reach 85 or more years of age. Even this age group has a per-driver crash rate lower than drivers younger than 50 years of age.
Figure 5. Crash Involvement Rate per Thousand Licensed Drivers by Age Group
		While the per-person rates reflect a smaller proportion of older drivers involved in crashes than younger drivers, adjusting the number of crashes by the total mileage traveled by members of each age group reveals a different pattern. Figure 6 shows the number of crashes per 100-million miles traveled. This curve indicates that the highest per-mile crash rates occur among the youngest and the oldest age groups. This demonstrates that an "average mile" driven by a member of one of these two groups is more dangerous than an "average mile" driven by a member of an intermediate age group. However, since drivers at either end of the age range drive far fewer miles than those in between, researchers have questioned the equality of those "average miles" across age groups. Unlike younger and older drivers, drivers in the intermediate age groups travel a sizeable proportion of their annual miles on expressways and other inter-city roadways. These types of roads typically offer fewer hazards than do roads in urban areas. Most of the miles driven by younger and older drivers involve congested areas and heavy concentrations of intersections that offer relatively more opportunities for conflict with pedestrians and other vehicles.
Figure 6. Crash Involvement Rate per 100 Million Miles VMT by Age Group
		Fatality rates reveal that older drivers are at increased risk of dying, whether the rate is based on the number of licensed drivers (shown in Figure 7) or on the total vehicle miles traveled (shown in Figure 8).
Figure 7. Fatality Rate per Thousand Licensed Drivers by Age Group
Figure 8. Fatality Rate per 100 Million Vehicle Miles Traveled by Age Group
		If drivers of any age were equally likely to die from crash injuries, then the shape of Figure 7 should be the same as Figure 5. This condition appears to hold for drivers below the age of 60 or so. However, drivers older than 60 years of age show increasing fatality rates, indicating that older drivers suffer more serious injuries in crashes than do younger drivers. This increase in driver fragility with age is shown more clearly by plotting the rate of fatalities per crash by age, as in Figure 9. On a per-mile basis, older drivers have a greater fatality rate than other-aged drivers. But by any other measure, younger drivers outnumber, out-travel, out-crash, and out-die older drivers. However, once they are in a crash, older drivers are more than three times as likely to die than are younger drivers.
Figure 9. Driver Fragility by Age Group

Characteristics of Crashes		By looking at the relative proportions of involvement in different types of crashes, it is possible to gain some understanding of the differences and similarities between age groups, independent of the absolute levels of involvement. Analysis of police crash reports contained in NHTSA's 5-State Crash Avoidance Research Data File (CARDFILE) reveals some striking differences and some surprising similarities between the crash patterns of younger and older drivers.
Time of Day		Figure 10 shows the hour-by-hour pattern of crashes by drivers of different ages. The younger-driver crash pattern does not differ much from that of drivers between the ages of 25 and 64, showing the majority of crashes occurring between 7:00 a.m. and 8:00 p.m., with a small peak during the hours of morning rush hour and a large peak during evening rush hour. After 8:00 p.m., the number of crashes declines slowly to a minimum around 4:00 a.m. (for 25 to 64 year-old drivers) or 5:00 a.m. (for 15-24 year-old drivers). Older drivers, on the other hand, have few crashes between 8:00 p.m. and 7:00 a.m. The crash patterns of older drivers do not show rush-hour peaks, but rather a slow increase in number from 7:00 a.m. to about 11:00 a.m., remaining flat until about 4:00 p.m., and slowly decreasing until around 8:00 p.m.

Crash Severity		Remarkably, the distribution of crash severity is almost identical across age groups, as shown in Figure 12. About 60 percent of all crashes involve property damage only; 22 to 23 percent involve possible injury; 12 percent non-incapacitating injury; 5 percent incapacitating injury; and fewer than one percent of crashes involve fatal injury. Among the fatal-injury crashes, the level of involvement increases with age, with 0.6 percent for drivers 15 to 64; 0.7 percent for drivers 65 to 74; and 0.9 percent for drivers 75 and older.
Figure 12. Percent of Crashes by Severity Level and Age Group

Number of Vehicles Involved		The majority of crashes involve two vehicles, regardless of drivers' age, as shown in Figure 13. Among younger drivers, two-vehicle crashes account for 68 percent of all crashes, compared with 71 percent of drivers 25 to 64, and 80 percent of drivers 65 and older. The percentage-point differences between age groups on two-vehicle crashes are largely made up in single-vehicle crashes. Proportions of single-vehicle crashes from the youngest to the oldest are 21 percent, 16 percent, and 10 percent, respectively.
Figure 13. Percent of Crashes by Number of Involved Vehicles and Age Group

Relationship to Intersection		Most crashes for all age groups occur at intersections, although the proportions are somewhat different for the different groups, as shown in Figure 14. About 50 percent of crashes of the youngest and middle groups occur at intersections, whereas about 60 percent of older drivers' crashes occur at intersections. Younger drivers show a greater tendency than other age groups to be involved in non-intersection crashes, with 15-24 age group showing 43 percent, the 25-64 group showing 41 percent, and the 65-74 group showing 31 percent.
Figure 14. Percent of Crashes by Relationship to Intersection and Age Group

Pre-crash Maneuver		More than half of the crashes of all age groups involve the vehicle going straight just prior to the crash, accounting for 59 percent of the youngest group's crashes, 57 percent of the middle group's crashes, and 53 percent of the oldest group's crashes. These proportions are shown in Figure 15. The most striking difference between the groups is in the proportion of crashes involving left turning. While 11 percent of younger drivers' crashes involved left-turning, 17 percent of older drivers' crashes involved left-turning. Within the older driver group, the oldest drivers show the greatest proportion of crashes in this category, involving 16 percent of 65-74 year-old drivers' crashes and 21 percent of the crashes of drivers 75 years old or more.
Figure 15. Percent of Crashes by Vehicle Maneuver and Age Group

Driver Error		Excessive speed is the primary error in 15 percent of younger-driver crashes, but only in about 5 percent of older-driver crashes, as shown in Figure 16. Right-of-way violations are the primary error in 18 percent of older-driver crashes, but only in about 9 percent of younger-driver crashes. Older drivers also make more errors at signed or signalized intersections than do younger drivers: 14 percent and 9 percent respectively. Driver inattention, which includes falling asleep at the wheel, was about equally likely among younger and older drivers, accounting for slightly more than 5 percent of crashes in each group.
Figure 16. Percent of Crashes by Driver Error and Age Group

Alcohol Involvement		Blood Alcohol Concentrations (BAC) at or above .10 percent are detected in about 6.5 percent of crash-involved younger drivers. Drivers between 25 and 64 years of age also show BACs at or above .10 percent in 6.5 percent of their crashes. Older drivers, however, show BACs at or above .10 percent in less than 2 percent of their crashes. These relationships are shown in Figure 17. Alcohol plays a much larger role in fatal crashes. One out of 10 fatal crashes in 1990 involved drivers or pedestrians with BACs between .01 and .09 percent, while 4 of 10 involved drivers or pedestrians with BACs at or above .10 percent. Twenty-seven percent of young drivers in fatal crashes had BACs at or above .10 percent, compared with 26 percent of drivers between 25 and 64, and 6 percent of drivers 65 years old or older.
Figure 17. Percent of Crashes by Driver Use of Alcohol or Drugs and Age Group

Sources of Risk for Younger Drivers: Problem Behaviors		The primary problems of drivers between 15 and 25 years of age appear to be related to lack of experience, immature judgment, and risk taking. Younger drivers have limited life experience to rely upon in developing responses to the driving environment. Some researchers contend that younger persons, especially in the teen years, have a sense of immortality and invulnerability to danger that carries over into their driving behaviors. Younger drivers tend to believe that crashes only happen to others. Some younger individuals also tend to display other characteristics that foster unsafe driving. Younger drivers perceive risk differently than older drivers. A NHTSA study found that younger drivers rated speeding as less dangerous than did their more experienced counterparts. There also was evidence that young drivers saw themselves as more skillful than their peers, and that young drivers' increased familiarity with a driving location reduced their perception of danger in that situation. This was not found for more experienced drivers. The findings suggested that, relative to drivers over 25 years of age, young drivers associated lower risks with certain driving acts and underestimated their personal risk of being involved in a crash. . Personality factors, particularly among males, may also contribute to the young driver problem. The literature includes references to over-expression of impulsiveness, daredevil driving, anger in traffic situations, and driving to let off steam after arguments. There also are weak but consistent correlations between various "anti-social" personality traits (more common among the young than other age groups) and higher crash rates.
Sources of Risk for Older Drivers: Declining Capabilities		The research literature confirms conventional knowledge about the effects of aging on cognitive, perceptual, and motor abilities. Age-related changes in vision make it more difficult for older adults to accommodate to darkness, recognize objects under low lighting conditions, recover from glare, and search their environment. Virtually all behavior slows with age, with performance decrements being more pronounced as task complexity and cognitive demands increase. Making decisions becomes more difficult, as does changing a course of action once a commitment has been made. Memory deteriorates with age, although the decline in healthy adults is not as great as previously believed. Short-term memory, in particular, is affected by aging. While few studies linked cognitive declines specifically to driving abilities, it is clear that these kinds of changes in abilities could pose problems for drivers who experience them. Experience and judgment are qualities that can contribute to compensating for slowed responses and sensory deficiencies. Evidence shows that most older drivers are aware of their changing abilities and adapt accordingly: making shorter trips totaling far fewer miles, and driving substantially less at night, in heavy traffic, and in bad weather. These self-regulated changes in exposure to risk largely account for the differences in crash characteristics between younger and older drivers. Driving problems increase with the seriousness of certain medical conditions. To the extent that older individuals are aware of their conditions, they tend to limit their driving appropriately. But, if they are victims of conditions of which they cannot be aware, they appear not to limit their driving and are consequently exposed to greater crash risk. Cognitive disorders, such as Alzheimer's Disease and difficulties performing tasks that require processing of several sources of information are among the most serious of these latter conditions. Older drivers' safety problems are exacerbated by increasing frailty. Drivers 75 years old or older are three times as likely to die in a crash than are 20 year old drivers.