U.S. Department of Transportation
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: FHWA-HRT-2006-004 Vol. 69 No. 6 Date: May/Jun 2006|
Publication Number: FHWA-HRT-2006-004 Vol. 69 No. 6
Date: May/Jun 2006
When making recommendations on infrastructure design, FHWA considers changes in the abilities of senior motorists and pedestrians.
|Older motorists like this woman will benefit from highway improvements such as improved intersections and larger street signs. Photos: NHTSA|
By the year 2030, one in five Americans will be age 65 or older. The fastest growing segment of the U.S. population is people more than 85 years of age. Every year, a growing portion of those who use the Nation's roads and sidewalks are older adults.
As people age, their abilities change. Some things, such as vocabulary and knowledge, can increase throughout a person's lifespan, but other abilities, such as vision, typically decline. Unfortunately, a large vocabulary does not help a motorist drive across town as much as acute visual ability does.
|Source: NHTSA Traffic Safety Facts 2004.|
The challenge for the transportation industry is to maximize safe mobility options for the older population while maintaining safety for all road users. "Understanding how the most common age-related abilities decline can help the transportation community design infrastructure to minimize the negative consequences of those declines," says Elizabeth Alicandri, director of the Federal Highway Administration's (FHWA) Office of Safety Programs.
The aging process is specific to each individual, although certain chronic medical conditions and associated functional limitations that can affect driving may become more prevalent with age. A particular medical diagnosis alone, however, does not guarantee functional decline in ability. Because of the diversity in how age affects different individuals, many older adults will continue to drive safely well into their retirement years.
"Many assume that all drivers become dangerous as they age," says Dennis Utter, director of the Office of Traffic Records and Analysis, National Center for Statistics and Analysis. "This possibility is a growing public health concern. On the one hand, the average annual driver involvement rate in police-reported motor vehicle crashes in the United States is 55 per 1,000 licensed drivers, while the corresponding rate for drivers aged 65 and older is only 28 per 1,000."
If measured by miles traveled, however, older adults may be at increased crash risk. According to National Highway Traffic Safety Administration (NHTSA) data from the mid-1990s, drivers aged 85 and older have about the same fatality rate per mile driven as 20- to 24-year-olds
The primary issue is the potential for increased deaths of both older drivers and older pedestrians. Older drivers are less a threat to other road users than they are to themselves. However, crashes lead to death more frequently for older people, who may be frail due to chronic medical conditions and may take much longer to recover from severe injuries.
|Source: Administration on Aging.|
Moreover, travel options other than driving are extremely limited in many areas of the United States. Driving remains the preferred mode, particularly where reliable and affordable alternatives do not exist. Driving can help maintain the benefits of personal mobility for seniors, both physically and socially. Loss of personal mobility, on the other hand, can lead to cascading negative effects such as depression, which can then accelerate physical and mental deterioration, leading to earlier hospitalizations and nursing home admissions. For a majority of older Americans, driving is the only "personal" mobility option they have ever known, and they have come to expect to maintain the privilege indefinitely.
In many urban areas, walking can be an enjoyable and healthful travel option for older adults. In fact, after driving, walking is the second most used travel mode by older people. Walking often is not an option, however, for both real and perceived reasons. Older pedestrians are more vulnerable to death or serious injury when struck by motor vehicles, and older adults sometimes cite personal security as a reason for not walking.
Given the necessity of driving and walking for many older adults, reviewing facts about their habits can shed light on the challenges. Seniors actually practice many safe driving behaviors. They are more likely to wear seatbelts and obey the speed limit. They are less likely to engage in some of the risky behaviors more common to younger drivers, such as talking on a cell phone or drinking and driving. Once they become aware of changes in their physical abilities, older drivers often begin to self-regulate by limiting their driving at night, in unfamiliar areas, on roads with heavy traffic, in bad weather, or alone.
Older drivers do have a higher crash risk in some conditions and locations. According to the FHWA publication Highway Design Handbook for Older Drivers and Pedestrians (FHWA-RD-01-103), older drivers are more likely than other age groups to have crashes at intersections, when making left turns, and on limited access highways when merging, exiting, or changing lanes. Some common areas of difficulty include yielding, responding to signs and signals, scanning the roadway environment, staying in their lane, keeping up with the flow of traffic, passing, and stopping.
What can be done to help older road users in the face of these changes in ability? According to a 2003 University of Michigan Transportation Research Institute report, Promising Approaches for Enhancing Elder Mobility, medical and transportation professionals agree that the focus of safety efforts should be on helping older drivers and pedestrians who are able to continue driving and walking safely to do so, rather than focusing on restricting all older drivers regardless of ability. The challenge is making roads safer and decreasing mortality while maintaining independence for older motorists and pedestrians. In other words, what can be done to plan for their transportation needs?
As mentioned earlier, aging is a highly individual process, and changes occur at different rates. After all, there are 80-year-olds who are more productive than many 18-year-olds. Some 70-year-olds look and act much younger than their years, whereas others already experiencing serious chronic illness feel and act even older. Still, a few functional impairments are more common than others. The focus in transportation planning is on the changes that most people will experience and the ways that infrastructure can be designed to make mobility easier and safer for them.
|Older adults such as the driver and passenger in this car differ in the rates at which their driving abilities decline.|
What actually happens to a person's eyes as they age? Two of the key changes occur in the lens, which focuses light on the retina. The lens becomes less flexible and yellows with age. The reductions in flexibility make it harder to shift focus from a near object to a far object. In fact, presbyopia, or nearsightedness, is a common age-related visual change. The yellowing of the lens and other changes cause older adults to need more light to see. Although they benefit from additional lighting, they also are more susceptible to glare and require significantly more time to recover from it. One of the major consequences of these and other vision changes is that it is harder for older people to see at night.
Other changes occur as well, such as declines in peripheral vision. Because of these changes, older adults often are slower to react to objects outside of their central focus. Natural declines in peripheral vision often are made worse by glasses, which usually improve focal vision rather than vision in the entire visual field.
|This older driver presumably checked her rearview mirror before backing out of her driveway. As people age, their peripheral vision and ability to shift focus from a near to a far object decline.|
A number of infrastructure measures can reduce the impact of vision declines. One of the most obvious steps is to enlarge roadway signs and lettering. If drivers can read the information from farther away, they will have more time to make navigation decisions and can focus on safe maneuvers. The Manual on Uniform Traffic Control Devices (MUTCD) recommends sign and font sizes for various types of signs. According to Hari Kalla, FHWA's MUTCD program manager, "The 2003 edition of the MUTCD includes increased letter sizes for street signs based on research recommendations for older drivers."
Curves present another visual challenge. Older drivers may not detect sharp curves, especially at night and wherever the retroreflective pavement markers have faded. Declines in contrast sensitivity (the ability to discern brightness differences between adjacent areas) make it harder for older drivers to notice faded pavement markings, but those markings provide extremely important information to drivers under dark or rainy driving conditions.
|This older driver is having his vision tested.|
One technique to improve curve detection for sharp curves is to use retroreflective pavement markings leading up to the curve and spaced throughout it. These pavement markings are highly visible at night, and researchers at FHWA's Turner-Fairbank Highway Research Center (TFHRC) are looking at configurations that will make it even easier for older drivers to detect sharp curves. Thomas M. Granda, Ph.D., team leader for the Human Centered Systems Team in FHWA's Office of Safety Research and Development, oversees the highway driving simulator at TFHRC. He says, "Our research team is using both the driving simulator and field research techniques to determine the best configurations for retroreflective pavement markings to make curve detection easier for drivers of all ages. And we involve older adults in all of our pedestrian and driving research."
People may move more slowly with age. Some older adults experience loss of limb strength, flexibility, sensitivity, and/or range of motion, or reduced ability to rotate the head and neck. Such changes may be the result of simple joint inflammation and deterioration (arthritis), muscle atrophy or paralysis related to stroke, or other problems. Chronic illnesses, such as coronary artery disease, heart failure and emphysema can greatly restrict and slow physical activity and mobility. General flexibility and head movements in particular are necessary to physically operate a motor vehicle, particularly for merging, lane positioning, and parking.
Reduced flexibility can affect a variety of driving tasks, especially where drivers have to visually scan a wide portion of the roadway environment. Some types of scanning cannot be eliminated, such as looking for other cars, pedestrians, or traffic signals, but it is important to avoid creating situations where excessive scanning is necessary. For example, consider skewed intersections where two roads meet at an angle that is less than 60 degrees instead of at a right angle. Because of their design, skewed intersections require more head movement and scanning. New highway projects should avoid skewed designs where possible. If a skewed intersection cannot be avoided, right turn on red should be prohibited because some older drivers will have a harder time detecting safe gaps in traffic.
The effects of age- and illness-related changes in flexibility on navigating skewed intersections are apparent. But physical difficulties may not seem relevant to providing advance guide and street signs. Advance information enables older drivers to ready themselves to make the appropriate responses, such as braking or turning. That small amount of extra time can make a difference. Advance signing enables drivers to focus on making a safe turn instead of having to look for a street sign at the same time.
|Many older drivers like this motorist may experience reduced range of motion, making it harder to rotate the head and neck and therefore more difficult to navigate skewed intersections|
According to NHTSA's Medical Conditions and Driving: A Review of the Literature (1960-2000), the source of the most commonly occurring traffic violations leading to increased crashes involving older drivers, such as failure to obey stop signs or unsafe left turns, is not an "obedience" problem but rather "attentional errors." Such errors may signal cognitive decline, which can develop from a number of conditions, such as the early stages of Alzheimer's disease. Cognitive abilities also may be affected by the interactions of various medications taken for a number of chronic conditions.
Working memory is the ability to maintain information active in memory. A classic example is learning a new phone number and trying to remember it until you can dial it. With age and illness, the working memory capacity—the amount of information that can be held in memory at one time—often declines. There are many different types of attention. Selective attention is used continuously to filter out extraneous sensory information in order to focus on critical information, though most people may be largely unaware that they are doing it. On the other hand, divided attention is used to monitor and respond to multiple events at the same time. An example is the combined tasks of entering a freeway while tracking the curvature of the ramp to steer appropriately and keeping a safe distance from the cars ahead. In general, older adults often find it harder to screen out unnecessary information, especially when they are in unfamiliar situations. They may encounter difficulties when performing multiple tasks at the same time.
Reaction time is the time from when a stimulus appears to when a physical response is initiated. The reduced muscular flexibility of older adults contributes to slower responses. One aspect of age-related slowing in reaction time is slower information processing in the brain. As a result, older drivers may be slower to react when a traffic signal turns from red to green or when applying the brakes during an emergency situation.
Redundant street name signs can be used to improve the chances of drivers remembering critical navigation information when they need it. At one time or another, most people have read a road sign, been distracted shortly afterwards, and then realized that they could not remember the instructions. The distraction essentially wiped the information out of working memory. Given that working memory capacity can decline with age, these types of lapses become more likely for older drivers. Providing the information several times can help limit this problem. The repeated messages create opportunities for drivers to notice the information they need in advance of a decision point so they can prepare to change lanes or turn if need be.
|This skewed intersection in Atlanta, GA, may pose a problem for older drivers. If a skewed intersection cannot be avoided, right turn on red should be prohibited.|
Older drivers often prefer driving in familiar and predictable circumstances. Unfortunately, roadways, even familiar ones, change. For example, work zones may jolt a driver's expectations because of sudden lane closures or detours. When a driver encounters new circumstances, an increased burden is placed on working memory and attention. The driver has to devote more attention and resources to determining how to navigate the new conditions.
Changeable message signs are one way that transportation agencies alert drivers to new circumstances, and designing the messages so that drivers can easily understand them is important. The last thing any transportation professional wants to do is present a message that confuses the driver. FHWA's Highway Design Handbook for Older Drivers and Pedestrians provides preferred strategies for presenting information on changeable message signs. Signs should be designed for a maximum of two phases (for example, phase 1: Road Work Ahead; phase 2: Left Lane Closed). For words that are too long to display, care should be taken in selecting abbreviations. What does ACC mean, for example? Does it mean "access" or "accident"? What about DLY? Is it "delay" or "daily"? The more time that drivers of any age have to spend figuring out a message means the less time they have to focus on safely operating their vehicles.
Some of the same declines in musculoskeletal and physical function that affect older drivers necessarily affect them as pedestrians too. For example, common hip and leg impairments such as arthritis can limit walking comfort and distance. Loss of limb strength, flexibility, sensitivity or range of motion, and reduced ability to rotate the head and neck all can make walking more challenging or impossible. Because walking is one of the most recommended ways for older adults to maintain health and prevent injury, the roadway infrastructure should help increase, rather than discourage, walking.
Just as roadways can be improved for older drivers, so may the infrastructure be enhanced for older pedestrians. According to 2004 NHTSA data on pedestrian safety, adult walkers over age 70 had the highest fatality rate of any pedestrians. Intersection improvements in particular are important because older pedestrians are overrepresented in intersection fatalities.
Many older adults walk more slowly than the MUTCD recommendation of 1.2 meters (4 feet) per second used for timing "flashing don't walk" signals. Slower walking speeds should be used to set traffic signal times in areas where a number of older adults are likely to be walking. The current MUTCD recommendation is based on the walking speeds of average, healthy adults, but the MUTCD allows for slower walking speeds where necessary. A walking speed of 0.9 meters (3 feet) per second covers nearly all walkers, including the elderly and people with disabilities.
|Declines in the working memory capacity of older people can affect memory of critical navigation information provided in signs. This change can be addressed in part through redundant street signs. Here, an older man is being tested by an Iowa driver licensing official.|
The National Committee on Uniform Traffic Control Devices has reviewed research on this matter and has recently recommended to the FHWA that the MUTCD guidance be revised to use a more refined process for determining pedestrian signal timing, using slower walking speeds. Such changes may be proposed in the formal rulemaking process leading to the next edition of the MUTCD.
Leading pedestrian intervals, which allow pedestrians at a crosswalk to start crossing before the light turns green for vehicles driving in the same direction, are also a good practice. The increased lead times improve pedestrian visibility in the crosswalk because they will have entered it before vehicles are allowed to make turns. Giving all pedestrians a headstart may be advantageous for older drivers as well, making it easier for them to see the pedestrians.
Countdown pedestrian signals can be another useful measure. They may reduce older pedestrians' worry about getting trapped in the road when the traffic light turns green.
Physical changes to the roadway environment can be helpful as well. Median refuges do what their name implies—they provide a safe midpoint for slower pedestrians who may not be able to complete a crossing in one cycle. In short, the transportation community has a number of tools at its disposal to help older pedestrians, and pedestrians in general, cross roads more safely and comfortably.
Many pedestrian-related infrastructure improvements will benefit everyone, including walkers of all abilities and wheelchair users. And many measures that enhance accessibility, per the Americans with Disabilities Act (ADA) and United States Access Board recommendations, often benefit older pedestrians as well. In fact, adding curb ramps, reduced cross slope, and clearing the sidewalk of obstructions are ADA design guidelines that probably improve conditions for all pedestrians.
"One of the first things municipalities need to do is to make sure that sidewalks are installed where they do not yet exist, and that all sidewalks are wide enough, unbroken, level, and not too close to high-speed roadway traffic," says John LaPlante, P.E., P.T.O.E., vice president and chief transportation planning engineer for T.Y. Lin International. "But there is a bit of a catch-22 that some measures which make it easier for the elderly to drive may increase traffic overall, making walking even less feasible for them in many areas," he adds. "One retrofit that might strike a balance between both needs is squaring corners off, or decreasing turning radii, which encourages all drivers to slow to make turns, and decreases crossing distances for pedestrians."
|Arthritis and joint replacements may limit walking comfort for older pedestrians. Reducing the MUTCD design standard for signal timing to 0.9 meters (3 feet) per second can help older pedestrians cross safely. Here, a police officer halts motorists to allow time for an older woman to cross an intersection.|
In the coming decades, older adults will comprise an increasing proportion of the U.S. population. This is a positive development for society because it indicates that people are living longer and healthier lives. But aging, and the chronic illnesses that become more prevalent with age, may bring about some changes in vision, cognition, and motor skills. These ability changes occur at different rates for different people, so it is incorrect to assume that all drivers of a certain age have deficits or are unsafe.
The transportation network must accommodate larger numbers of older drivers, pedestrians, and public transit users. Maximizing their ability to use the network is important since transportation plays such a significant role in maintaining independence. To the extent that older adults can safely drive or walk on their own, they will be able to preserve their quality of life.
"Thankfully, most of the infrastructure changes that communities make for older road users benefit users of all ages and society as a whole," says FHWA's Alicandri. "There are very few, if any, infrastructure recommendations that benefit older adults but hinder other road users. If you're not already an older road user, one day in the future you will be—and these infrastructure changes will help ensure that you will be able to get around safely on your own."
Lisa Phillips coordinates the American Medical Association's (AMA) Older Drivers Project. She holds a degree in urban planning from the University of Illinois at Chicago and is a bicycling and walking advocate.
Gabriel Rousseau, Ph.D., is a transportation specialist in the FHWA Office of Safety Programs in Washington, DC. He has a Ph.D. in cognitive psychology from The University of Georgia. He works on human factors and pedestrian/bicyclist safety issues.
Joanne Schwartzberg, M.D., is the director of Aging and Community Health at AMA, and she also directs AMA's Older Drivers Project.
For more information, contact Gabriel Rousseau at 202-366-8044 or firstname.lastname@example.org.