Table Of ContentUMTRI-98-9
VEHICLE LIGHTING AND
THE AGING POPULATION
Kåre Rumar
June 1998
VEHICLE LIGHTING AND THE AGING POPULATION
Kåre Rumar
The University of Michigan
Transportation Research Institute
Ann Arbor, Michigan 48109-2150
U.S.A.
Report No. UMTRI-98-9
June 1998
TechnicalReportDocumentationPage
1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No.
UMTRI-98-9
4. Title and Subtitle 5. Report Date
Vehicle Lighting and the Aging Population June 1998
6. Performing Organization Code
302753
7. Author(s) 8. Performing Organization Report No.
Rumar, Kåre UMTRI-98-9
9. Performing Organization Name and Address 10. Work Unit no. (TRAIS)
The University of Michigan
11. Contract or Grant No.
Transportation Research Institute
2901 Baxter Road
Ann Arbor, Michigan 48109-2150 U.S.A.
12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered
The University of Michigan
14. Sponsoring Agency Code
Industry Affiliation Program for
Human Factors in Transportation Safety
15. Supplementary Notes
The Affiliation Program currently includes Adac Plastics, BMW, Bosch, Britax International,
Chrysler, Corning, Delphi Interior and Lighting Systems, Denso, GE, GM NAO Safety Center,
Hella, Hewlett-Packard, Ichikoh Industries, Koito Manufacturing, LESCOA, Libbey-Owens-Ford,
Magneti Marelli, North American Lighting, Osram Sylvania, Philips Lighting, PPG Industries,
Reflexite, Stanley Electric, Stimsonite, TEXTRON Automotive, Valeo, Visteon, Wagner Lighting,
3M Personal Safety Products, and 3M Traffic Control Materials.
Information about the Affiliation Program is available at: http://www.umich.edu/~industry/
16. Abstract
Old drivers and old road users in general, have high injury and fatality rates in road traffic.
Furthermore, the proportion of old road users and old drivers will increase rapidly during the
coming decades. Night travel has proven most difficult for old persons. The purpose of this study
was to analyze this situation from the vehicle lighting point of view in order to propose vehicle
lighting improvements that could be of special benefit to old road users.
A literature review of current knowledge concerning age, visual performance, and accident
involvement was carried out. This was followed by an analysis of the present vehicle lighting
problems. Based on the results from these analyses, a number of proposals for improvements were
presented. The main proposals concerning illumination systems are as follows: more illumination
to increase visibility in spite of higher glare, wider illumination to improve road guidance, a softer
cut-off to decrease aiming sensitivity, and keeping headlights clean and correctly aimed. The main
proposals concerning signaling and marking lights are the following: two intensity levels (for day
and night), small, high-mounted turn signals, and higher light-source reliability. Mandatory daytime
running lights are proposed. Interior lighting should be improved in a number of aspects. All of
these proposed improvements should be beneficial not only for old drivers, but also for other
drivers. Finally, the visibility and safety effects are estimated, research needs are pointed out, and
technical and economic problems are discussed.
17. Key Words 18. Distribution Statement
vehicle lighting, vehicle signaling, headlighting, age, old drivers, Unlimited
literature review, improvement, countermeasures
19. Security Classification (of this report) 20. Security Classification (of this page) 21. No. of Pages 22. Price
None None 94
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Acknowledgments
Appreciation is extended to the members of the University of Michigan Industry Affiliation
Program for Human Factors in Transportation Safety for support of this research. The current members of
the Program are:
Adac Plastics
BMW
Bosch
Britax International
Chrysler
Corning
Delphi Interior and Lighting Systems
Denso
GE
GM NAO Safety Center
Hella
Hewlett-Packard
Ichikoh Industries
Koito Manufacturing
LESCOA
Libbey-Owens-Ford
Magneti Marelli
North American Lighting
Osram Sylvania
Philips Lighting
PPG Industries
Reflexite
Stanley Electric
Stimsonite
TEXTRON Automotive
Valeo
Visteon
Wagner Lighting
3M Personal Safety Products
3M Traffic Control Materials
Appreciation is also extended to Michael Flannagan, Michael Sivak, and Robert Sweet for their
valuable assistance in editing this report.
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Executive Summary
The purpose of this study is to analyze existing literature and general knowledge in order to
describe problems with present vehicle lighting systems (illumination, signaling, marking, conspicuity, and
interior) related to aging road users, and to propose lighting modifications and measures intended to
counterbalance such age-related problems. There are three main reasons for doing this study. One reason
is that the number of old persons in road traffic during the next twenty-five years will increase faster than
any other road user age group in the developed countries. Another reason is that old road users are found
to have high risks in road traffic. The third reason is that nighttime driving is perceived by old persons as
very difficult and dangerous.
Initially a review is made of present knowledge concerning problems with old persons in road
traffic. It is concluded that mobility is an important variable in present social and professional life. But old
persons restrict their traveling substantially because they find it difficult and potentially dangerous.
Concerning drivers, this self-restriction typically includes refraining from driving at night, on icy roads, in
rush hour, in rain, through intersections, and in reverse.
It is common to distinguish several aspects of aging. One aspect concerns the central nervous
functions and is often called cognitive. The main effect of aging on the cognitive functions seems to be
difficulties in handling complex and novel situations, especially under time pressure. This leads to divided-
attention problems, missed stimuli, distraction, and long decision and reaction times.
Several countermeasures have been proposed to reduce the high accident involvement of old road
users. These fall into three general categories: (1) restrict the driving of old persons, (2) inform, educate,
and train old persons about their driving capacities and risks, and (3) facilitate mobility for old road users
(including drivers). Driving restriction is important for those who do not realize their own limitations, while
information, education, and training can be helpful to those drivers and others. Finally, in order to
participate in society and to continue to live active lives, old persons need mobility. Therefore the third
approach—change the conditions so that the old persons can maintain their mobility—is the best
countermeasure whenever it is possible.
Another aspect of aging concerns physiological impairment, primarily of the senses. The
impairment of hearing is of secondary importance to drivers, but it is of primary importance to pedestrians
and cyclists. Vision is the main sense for moving in road traffic. There are many visual functions that
deteriorate with age: decreased pupil size, more distant near point, smaller number of active receptors,
decreased eye-movement capacity, reduced capacity to adapt to low light levels, reduced visual acuity,
reduced contrast sensitivity, impaired peripheral vision, higher glare sensitivity and longer glare recovery,
impaired color vision, and reduced speed and motion perception. Some of these deficiencies are related to
changes in more central capacities. Examples of such functions are visual search, divided attention, and
useful field of view. None of the relatively simple visual functions shows high correlation with driver
accident involvement. However, more complex functions such as divided attention and useful field of view
appear to be more predictive of accident involvement.
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The performance of present vehicle lighting systems under realistic, real-world conditions is not
fully reflected in how they perform when formally tested for compliance with regulations. Especially the
illumination systems, but also the signaling systems, are designed for ideal situations and do not perform
equally well in the full range of real traffic situations.
To analyze the problems that old persons have with various vehicle lighting systems, and the
countermeasures that could be suitable, three approaches were taken using accident data, knowledge about
changes in visual performance with age, and finally a formal driver model. The conclusions from these
analyses were used to make a number of proposals for modifications of vehicle lighting systems to
facilitate visual tasks, especially for old road users.
The main problem in adapting low-beam headlighting systems to the old road user is the balance
between increased illumination for better visibility and decreased glare. It is suggested that, despite higher
glare sensitivity, the old driver would benefit from more illumination. In order to decrease the sensitivity of
headlighting to changing conditions (mainly road geometry) a comparatively soft cut-off is desirable. The
headlights should be kept in better condition (with regard to aiming, dirt, haze, scratches, voltage, bulb
failure, etc.) than is presently the case. Furthermore, because of the impaired road guidance experienced by
old road users, more light along the road sides would be beneficial.
Dual-level signal lights should be introduced in order to compensate for the reduced contrast
sensitivity of old persons. Furthermore, the maintenance of the signaling and marking lights should be
improved. Turn signals should be made smaller, and should be positioned higher up on the vehicle, to be
more in the central field of the other road users. Turn signals should also be separated from the headlights
and other rear lights. Some type of contour marking of vehicles should be introduced to facilitate distance
estimation, especially for old road users.
Two front daytime running lights (DRLs) should be mandatory to facilitate the detection of other
vehicles during daylight. Low beams seem to work fine as DRLs, but are not optimal from a lighting
engineering point of view. A wide light distribution is appropriate. No other lights should be on together
with the DRLs. The switching should be automatic.
Present interior lighting in cars could be substantially improved. Interior lighting of controls, of
handles and locks, of storage compartments, for reading, and for stepping in and out of the car should be
improved.
The potential improvements in visibility distances due to improved illumination systems are
estimated to be 10 to 20 percent. The safety effect will be smaller—probably a reduction of nighttime
accidents by 1 to 2 percent. The proposals for improvement of signaling and marking lights may reduce
vehicle collisions by up to 5 percent. DRLs should reduce daylight collisions by about 5 percent. Interior
lighting improvements will mainly improve comfort and only indirectly have any effect on safety. The
proposed changes should be favorable also for other road user groups—not only for old road users.
Finally, some comments are made concerning basic and applied research needs, and technical and
economic problems. None of the proposed vehicle lighting appears to be technically impossible or
prohibitively expensive.
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Contents
Acknowledgments iii
Executive Summary v
1. Age-Related Problems in Traffic 1
1.1. Road-user age, exposure, and road accident statistics 1
1.2. The effects of aging on various non-visual functions 7
1.3. Previously proposed countermeasures to reduce the high road accident rate
of old road users and to compensate for their functional problems 10
2. Age-Related Vision Problems 13
2.1. Age and vision 13
2.2. Age, vision, and accident statistics 19
2.3. Previously proposed countermeasures to compensate for the degraded
visual functions of old road users 20
3. Present Road-Vehicle Lighting and Road-User Age 23
3.1. Vehicle lighting: goals, requirements, and reality 23
3.2. The importance of visual performance in actual traffic 33
3.3. Age and vehicle illumination 36
3.4. Age and vehicle signaling and marking 45
3.5. Age and vehicle conspicuity 47
3.6. Age and interior vehicle lighting 47
4. Proposals for Age-Based Modifications of Vehicle Lighting 49
4.1. Proposals for illumination systems 49
4.2. Proposals for signaling and marking systems 58
4.3. Proposals for conspicuity systems 63
4.4. Proposals for interior lighting 65
5. Conclusions 67
5.1. Safety 67
5.2. Safety effects of lighting improvements 69
5.3. Technical aspects 71
5.4. Economic aspects 73
5.5. Research needs 73
6. References 77
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