Characteristics of older road users and their effect on road safety

Accid. Anal. and Prev., Vol. 27, No. 3, pp. 391-404, 1995 Copyright 6 1995 Elsevier Science Ltd Printed in the USA. All rights reserved ooLI-4575/95 $9.50 + .oo

Pergamon 0001-4575(94)00077-8

CHARACTERISTICS OF OLDER ROAD USERS AND THEIR EFFECT ON ROAD SAFETY YASUO MORI’ and MITSUO MIZOHATA~ ‘Department of Civil Engineering, Faculty of Engineering, Osaka University, 2-l Yamadaoka, Suita, Osaka, Japan; *Department of Civil and Ocean Engineering, Faculty of Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Japan (Accepted

25 July 1994)

Abstract-This paper reports the results of several field surveys on the characteristics of older road users in Japan and of their traffic accident statistics. The results obtained are as follows: the reduced physical and mental functions with advancing age give improper driving characteristics to elderly drivers, but are not deterministic factors of quitting driving; the driving characteristics have some relation with traffic accidents; problematic drivers seem to emerge among elderly drivers; reduced functions are also related to the occurrence of accidents among elderly people in bicycle riding and walking. Further, a systematic and comprehensive approach is presented for traffic accident prevention among the elderly based upon these results. Keywords-Older approach.

road user, Traffic accident,

Travel

INTRODUCTION

characteristic,

Giving up driving,

Comprehensive

his skills related to travel behaviour go down. It may be necessary for some older drivers to give up driving. Therefore, careful consideration will be required so that there is no negative impact on the quality of life of such drivers who are obliged to give up or who voluntarily quit driving. This paper reports the results of several field surveys on the characteristics of elderly road users in Japan and of their traffic accident statistics. Furthermore, a systematic and comprehensive approach, based upon the results, is presented for prevention of traffic accidents involving elderly people.

Traffic accidents caused by elderly people are increasing in number and the mortality rate for these accidents is higher than that of accidents caused by young or middle-aged people. However, we cannot support a view that the increase of elderly people will directly result in an increase of traffic accidents. In the 197Os, called a period of “traffic war,” traffic accidents caused by physically and mentally immature youngsters, who formed a high percentage of the population because of the second baby boom, had already shown a drastic increase. This can be attributed to a series of traffic safety measures, including hardware improvements of guardrails, pedestrian bridges, crossing underpasses, and traffic signals and signs as well as software dynamics such as promotion of going to and coming back from school in groups among primary school children. It is clear that these measures were effective because the majority of accidents had been those between pedestrians and vehicles. To cope with the prevention of accidents caused by elderly persons, there is a need to address the issue based upon a detailed analysis of the reduced physical and mental functions of such persons and of the characteristics of their accidents and to review the road improvement plans and traffic safety plans, including the appraisal of their investment efficiency. As the age of a person goes up beyond 55-60,

RELATIONSHIP BETWEEN AGE AND PHYSICAL/MENTAL FUNCTIONS The physical and mental functions used at a traffic scene are classified into four categories (Department of Roads 1990). Eyesight and hearing are used by drivers to recognize their environmental situations. Judgment and reaction are functions for analyzing the recognized situations and reacting to the outcome. In terms of functions directly related to driving, the main factors seem to be eyesight, judgment, and reaction. Hearing is specifically responsible for gathering information from behind, when one is walking, riding a bicycle, or driving a motorcycle. 391

392

Y.

MORI

and

Eyesight weakens with age (Burg 1967; Shinar 1977; National Police Agency 1985; Vehicle Safety Driving Center 1987). Static visual acuity (SVA) starts to slow down around 40 years of age. SVA at 65 years old and over is approximately 80% of that of people in the thirties. Dynamic visual acuity for moving objects begins to deteriorate in the fifties and that of people over 65 years old is less than 50%, compared to that of young or middle-aged people (Burg 1964; Shinar and Schieber 1991; Klein 1991). Visual acuity at night is also reduced by 30% and recovery time from glare is twice or more longer in the same comparison (Burg 1967; Sivak, Olson, and Pastalan 1981; Olson 1988). The rate of failure of people in their thirties or forties to recognize distance to moving objects is less than lo%, and the same rate for people over 65 is about 20%. Recognition of distance to an obstacle in front of older people is apparently inferior to that of young people (Henderson and Burg 1974; Johnson and Keltner 1983; Hill and Mershon, 1985). Descent of the eyelid limits the upper visual field and the peripheral sight is narrowed (Ubunai, Shioji, and Suzumura 1983; Klein 1991). In addition, elderly people tend to fix their eyes on swiftly moving objects coming towards them, as confirmed in eye-mark tests (Shimizu and Kimura 1992), and to tire quickly in flicker tests (Mukai 1983). Senile cataract makes the lens a cloudy yellow and creates vision as through yellow glass. Center lines and traffic signs and signals that are yellow color are recognized as close to white (Yoshida 1983; Klein 1991). Over the age of 65 years, roughly 30% of hearing is lost, mainly at higher frequencies. A serious disability called senile hyperacusia, if it occurs, shuts out almost all information through sound (Rees and Botwinick 1971; Bromley 1974). The major index for performance of the functions relative to judgment and reaction is reaction time. Judgment of information in the elderly slows down and becomes more incorrect due to their reduced eyesight and deteriorated nervous system. Transmission time of information from nerve to muscle becomes longer for people over 40 years old. Simple reaction time represents “swiftness of reaction.” The reaction time of old people is 30% longer than that of young people. In an alternative selection test that examines both swiftness of reaction and accuracy of judgment, functional deterioration is even greater and the ratio of that of older people to that of young people is 1.6. When the number of alternatives for selection increases and swiftness of response is required, delay time of response is longer and the error rate becomes higher (Vehicle Safety Driving Center 1987; George and Ariella 1992). The Swedish Road and Traffic Research Institute reports

M. MIZOHATA

that delayed reactions seen among older drivers are related to deterioration of sophisticated functions such as cognition and short-term memory, rather than to deterioration of perceptive functions (Rumar 1987). Muscle and its movement are no exceptions to deterioration with advancing age, either. The number of muscle fibers is normally maintaiend but diameter and flexibility of the fibres are physiologically lost as age increases (McComas et al. 1971). Grasping power and dorsal muscle power are lost and the movable range of the neck and waist is reduced. Some older people suffer from arthralgia, and associated changes naturally limit free actions of head and waist, consequently impeding smooth and swift steering, especially in backing up (JTSEA 1979). The stride length of older people is about half that of young people. Walking speed is much slower, and time for a first step from standstill is longer. Swaying walk or sliding walk begins to emerge among older people (Tokuda et al. 1984; Tokuda 1987). The swiftness, correctness, and balance of their actions are reduced. Furthermore, some older people are fragile and subject to disease. Several neuropathological studies indicate that approximately 30%-50% of older drivers with dementia (predominantly Alzheimer’s type) are involved in traffic accidents (Evans et al. 1989; Kaszniak, Keyl, and Albert 1991). Parasuraman and Nester found that some attention skills of these drivers are related to the traffic accident rate (1991). The above psychological, physiological, and pathological findings indicate that such functions as eyesight, audition, judgment (attention), and reaction deteriorate with advancing age, even though individual variation caused by eating habits and exercising practices of individual is very great (Morse 1993; Schaie 1993). Advanced stages of deterioration would mean that many older people would have several handicaps. However, most old people have superior characteristics such as psychological stability and deeper insight backed by ample experience, compared to young or middle-aged people. TRAFFIC ACCIDENT CHARACTERISTICS OF ELDERLY DRIVERS First of all, the historical changes in Japanese traffic accidents are illustrated by recent statistics (GAA 1993). Since 1979, the number of traffic accidents once again has climbed and recently the annual number of traffic deaths exceeded 11,000. No wonder this situation is called the second traffic war. Figure 1 illustrates the growth rate in the number of

Characteristics

393

of older road users

2007

-

0l

‘79 ‘80 ‘81 ‘82 ‘83 ‘84 ‘85 ‘86 ‘87 ‘88 ‘89 ‘96 ‘91 ‘92 Note : l)Source,

GM ( 1993 )

2)The figures

in parenthesis

indicate

the number of deaths in 1992. Fig. 1. Change in the number of traffic deaths, classified by age group.

traffic deaths classified by age group. The increase for older people is notable. Figure 2 shows the number of deaths by age group for 100,000 people. The rate for the same group is also remarkable. The number of traffic deaths of those over 65 years exceeds that of those 16 to 24 years, since the portion of older people in the population is rapidly increasing.

Figure 3 illustrates the growth rate in the number of traffic deaths among the elderly, classified by transportation mode, and not all the decedents in this figure were passengers. The growth of deaths caused during car driving is the greatest among the elderly. Based upon these statistics, it is seen that traffic accidents involving old people have contributed to

‘79 ‘80 ‘81 ‘82 ‘88 ‘84 ‘85 ‘88 ‘87 ‘88 ‘89 ‘90 ‘91 ‘92 Note : lXiource,

GM (1993)

2)The figures

in parenthesis

are indices.

( The value for 1979 is set as 100.1 Fig. 2. The number of deaths in traffic accidents per 100,000 persons, classified by age group.

394

Y. MOIU and M. MIZOHATA

B’

, , , , , , , ‘79 ‘88 ‘81 ‘82 ‘83 ‘84 ‘85 ‘86 ‘87 ‘88 ‘89 ‘96 ‘91 ‘92 1

,

Note

:

I

I

l)Source,

I,

,

GM (1993)

2)The figures

in parenthesis

indicate

the nuabsr of deaths in 1992. Fig. 3. Change in the number of deaths by traffic accident among older people, classified by traffic mode.

a large extent to the recent accelerated aspects of the second traffic war. At present, accidents involving pedestrians and bicycles are greater numerically than accidents caused by automobiles. However, as a consequence of the aging process of the driver population, further increase in accidents involving elderly drivers is likely to occur. Secondly, the occurrence rate of traffic accidents, adjusted by traveling distance per driver, is discussed. The rate sharply rises as the age of drivers goes up after 60 (Mizohata 1986b; Huston and Janke 1986). For older women drivers, the so-called J curve shifts to a higher position (Mckelvey et al. 1988). The same rate, broken down by driving experience, also represents the J curve (Leygue, Duflot, and Hoffman 1976). This fact does not mean that all elderly drivers are dangerous. It also cannot be denied that the reduction of distance travelled inflates with this rate. However, this fact suggests the existence of problematic drivers among older drivers. Thirdly, an analysis of the detailed aspects of the traffic accidents caused by young, middle-aged, and elderly drivers leads to the following findings. Elderly drivers tend to provoke accidents at intersections (Mizohata 1986a), and this seems to be true even in the United States and European countries (Cerrelli 1989). Supposedly, such drivers cannot properly act at intersections where more complex information handling and more appropriate judgment are required than in any other place. Another breakdown of intersection accidents revealed the

following tendencies. Elderly drivers as assaulters involve a vehicle in the opposite lane or a vehicle at their sides in an accident when they are turning right (Mizohata 1986a). In contrast, elderly drivers become victims of being hit from the rear while their vehicles are temporarily stopped (Mizohata 1986a). The former case is explained by the fact that the amount of information to be recognized and analyzed for a right turn (for a left turn in Europe and the United States) is greater than that for a left turn (Staplin and Fisk 1991). As described before, elderly drivers are generally not good at quick response and occasionally omit certain driving procedures. The latter has something to do with their tendency to stop their vehicles where such actions are not expected by others, as is discussed again later. Intersections with unusual shapes could easily cause more pressure to old drivers, since their deteriorated functions face elevated necessities to handle complex information. An analysis was made with intersection accidents involving older or younger drivers, using factors specific to the intersections (Mizohata 1989). Categorical data on each factor were collected through a field survey. Table 1 illustrates the results of applying Hayashi’s quantification analysis to these data (Hayashi 1976). The values of score to each category are computed so that the correlation ratio ($ would be maximized. The absolute value and signs correspond respectively to the length and direction of lines drawn in the right column. Hit ratio (F) is the rate that can correctly discriminate between intersection accidents involv-

Characteristics

Table 1. Discriminant analysis of traffic accidents younger and older drivers at intersections Factor

N

c1terorm T-shape

of

shrpe

crossing

146 73

Yes

Lane for right turn

“0

23

with

40

without

Oifference of

under 3 meters over

Sirnnl

9l

4 meters

16

with

230

without

56

with without

20

Sign of

Yes

63

temp.

“0

7

223

nmber of

'L

62

rood

Total

_F

204

medium

stoP

0

63 193

bad Sight

L

113

width

lark

-r 1

246

0 meter

Road edre

vounr

0 3

263

266

_

DRIVING CHARACTERISTICS OF ELDERLY DRIVERS AND THEIR INTENTIONS TO QUIT DRIVING

~-0.324

SPoPIIS F=65.3

Note) N : No.

of samPIes,

1

:

correlation ratio. F

:

First, the driving characteristics of elderly and younger drivers are compared. These characteristics were observed from films of the drivers in action taken from the top of building along the road side (Mizohata 199Oa). The films were taken intermittently at intervals of 0.5 seconds and analyzed by the A/D conversion technique of photographic surveying. The purpose of the survey was to collect data on drivers’ behavior that was not influenced by voluntary actions for compensation and without any bias due to very small samples and also to study new technological findings to be requested for roads in the near future. The distinction between elderly and young drivers was confirmed by eyewitness of two assistants standing on the side of the road. Sepa-

Nat ratio

ing old drivers and intersection accidents involving younger drivers on a composite variable computed by adding their scores (Hayashi 1976). Findings obtained from these results are as follows: accidents of older drivers tend to center around those intersections that have an irregularly shaped crossings with more than four branches or the shape of a T connecting three branches, and that provide clear sight little ambiguity concerning the right of way (classified in “over 4 meters” in the “difference of width” variable in the table). In other words, “careless and

z

395

absent-minded driving,” probably caused by their reduced sight and judgment functions, have much to do with this aspect of accidents at intersections. In the meantime, older drivers have fewer traffic accidents at night and during long driving trips. They tend to drive at prudent speed and have fewer violations against traffic laws and regulations. These driving attitudes may be reflected by their lower risktaking tendency and more stable mentality. The above analysis can be summarized as follows: older drivers usually tend to compensate for their reduced abilities in sight and judgment by cautious driving, but regardless of such efforts some of them face a high probability of being involved in traffic accidents that have a close connection with reduced abilities.

21

+-rho&w others

SloPe

of

SCOW

Old0

46

irregular T-shape

of older road users

1 NO.5 section I in Saibi intersection Old q Non-old __.__.__._.- ._._._.__. --.--._._.- ._._.__.--.- _._._.-._.-.__.__.__.-._.-._._.__.__._-.-._.-._.-.-. I -Direction of left roadside me=22.4(m) m21.5(m) ve+.48tm? v=0.64(rrh _-.-- ._._._._.-.._ -.--.- _._._.-.-.-.--.-__.--.-.-.- .._.__, “_.

i I;:

19.5

20.0

20.5

21.0

21.5

22.0

22.5

23.0

23.5

tm’

Fig. 4. Distributions of running position of older and younger drivers. n, m, and v in the figure are the number of samples, mean value, and variance, respectively. The subscript, e, shows older drivers.

Y. MORIand M. MIZOHATA

396

Standard 3.0

deviation 2.0

2.5

of

speed (m/set)

Mean speed (m/set)

1.0

5.5

I

1.5 section

No. I(

I-meter

6.5

5.0

6.0

interval

)

7.0

;Ii \. 1

Standard of

Uean of

deviation

position(m)

position(m) Note

; Pe , Position P

,

Se , S

,

Position

of older drivers of younger drivers

Speed of older drivers Speed of younger drivers

Fig. 5. Positions and speed while taking measures to avoid oncoming vehicles.

rate samples of both groups were randomly collected based on the correspondence of judgment between the two assistants. Therefore, many drivers over 75 years of age are included in the samples of elderly drivers. The result revealed the following comparative characteristics of elderly drivers on ordinary roads: 1. Their driving speed is slower. 2. The space left between them and the vehicle in front is greater. 3. The running position in the lane is more to the left. (Figure 4 shows the distribution of running position of elderly and nonelderly

drivers at No. 5 section in Saibi intersection. The horizontal axis indicates the distance from the base line. Positive direction on the axis corresponds to the left side of the course of their vehicles.). 4. A tendency to drive in the outer lane is common. c Positioning on the curve section is more J. unstable. On narrow roads without center lines: 1. Flexible driving in the case of avoiding an oncoming car is seldom seen. Figure 5 illus-

Characteristics

397

of older road users

._

+Direction left

of roadside

Fsl

I

Old 3 m - ..I.._.._..._.._... -..-.._.,_.._..__.,_. o r-w131 5 me=7.1 Cm) z ve=0.3(mz)

5.5 Fig. 6. Distributions

6.0

6.5

‘7.0

at

driving less than

60 years

8.5

(m)

old

2. Distribution of running positioning has 2 peaks (Fig. 6). 3. A tendency to stop without paying much attention to cars behind is seen. The findings concerning positioning at the left side of a lane and choosing the outer lane can be interpreted as a result of safer positioning, reflecting the older driver’s tendency to pay much attention to fast moving objects (Shimizu and Kimura 1992). Driving without flexibility and stopping the vehicle seems also to be evidence of the fact that there are older drivers who suffer from deteriorated eyesight and lack of ability for quick handling of complex information (Brouwer, Waterink, and Wolffelaar

. . . ...

......

141 Al resay utxxased mved 78

Not driving

8.0

of running position of older and younger drivers on a narrow road.

trates the running position and speed of elderly and nonelderly drivers in the case. Avoidance of an oncoming car appears at any point in a closed interval of the survey road. Therefore, assuming that oncoming cars pass by the cars of both driver groups at No. 11 section on Fig. 5, all coordinates of the cars of both groups within an interval of 20 m including the section are transformed by parallel translation. The difference between two driver groups in position and speed is not statistically significant on average, but statistically significant in variance. Variances of position and speed for elderly drivers are smaller.

Still

7.5

at

or

al

I ._..

73

Have cant i tmed driving until some Years before 60, but rot driving at present 91 Have cant i nued driving unti years after 60. but not driving at present 146

Fig. 7. Quitting of driving observed among older drivers.

60

398

Y. MORI and M. MIZOHATA

1991). An experiment on car driving conducted in the United States has also shown significant differences between young and older drivers on speed maintenance and course selection at right or left turn and at lane changing (Brainin 1980). Next, whether or not awareness of reduced functions prompts older drivers to quit driving is discussed. Old drivers are considered to be veteran drivers. They enjoy social and leisure activities, using cars. Not many of such drivers think of quitting driving, knowing that their mobility cannot be maintained if they do so. Under the current Japanese driving license system, the number of drivers who have quit driving cannot be determined. Therefore, a mail survey has been conducted on possible voluntary quitting of driving by such drivers who are assumed to be over 60 years, whose names and addresses were retrieved from license registration cards (Mizohata, 1988). The return rate for this survey was as high as 43%. The percentage of respondents over 75 years old to all respondents was slightly higher than the similar percentage computed by another random sample of the elderly drivers who owned cars (Mizohata 1986b). Figure 7 illustrates the results of the survey on quitting driving. The rate of quitting driving differs, depending upon the definition. If we take the balance of deducting the number of the respondent drivers under 60 years old and of those deceased or moved from the total number of the replies as the denominator, and the aggregate number of drivers who have quit driving before or after 60 years old as numerator, the rate is 22% ((164 + 146)/ (1621 - 141 - 78)). If we deduct the number of drivers who have quit before 60 from both the denominator and numerator, then the rate is 12% (146/(1621 - 141 - 78 - 164)). The exclusion of the drivers who have quit before 60 makes this difference, and 10% to 20% of the license holders over 60 years old are people who have supposedly quit driving. Furthermore, interviews and a supplementary survey were carried out for the drivers chosen randomly and for all the drivers who have quit driving among respondents of the above mail survey (Mizohata 1989). The purpose of the interviews was to know the visual, cognitive, and socioeconomic characteristics of the target drivers and the purpose of the supplementary survey was to study the characteristics of their access to public transportation. The results were analyzed by a binary logit model that explains the choice for quitting driving or not. As is shown in Table 2, the following conclusions were obtained; first, the characteristics of the visual and

Table 2. Estimation result of binary logit model (Choice of driving or quitting) Factor

Paraneter

Constant

-6.9

dumny

sen AL e Occupatioh Type

of

No.

of

(t-value)

(-2.8**)

-0. 1 (-3.7**j

housing household

Annual

members -

income

Parking

2.2 ( 3.2**)

availability

Access

to

nass

Travel

time

to

Arithmetic

CBD 0

-

CDS)

0

-

(BD)

0

-

(A)

Digit

span

Block

design

-

transit

SVA

0 0

DAI

Spot Glare

(SC)

P2

- value

Uit

ratio

-

0

15 69.0 0.

Note; I)**

indicates

Z)These test

tools

studres A, and SC

statistical

factors

space

movement.

and

BD

0

the

[ Birren

DS and

show

with

tools

1963.

show

and

0 are

visual glare

are

on

and

ability.

respectrvely. acuity.

at

obtained

based

Henderson

calculation

ConstructIon.

static

significance

or

visual

1%

level.

by

sow

two Burg

previous 1974

short SVA. field

I.

memory. DAI

and

and eye

recovery.

cognitive functions will not be the reason for quitting driving, and second, the probability of driving decreases as the driver’s age increases, but, in contrast, if a parking lot is available at their homes, the probability will increase. The first conclusion indicates that there are drivers who do not want to quit driving even though some functional reductions are recognized. On the other hand, the age of drivers has a high positive correlation with the drivers’ uneasiness in driving. This supports the interpretation that the age of drivers increases the uneasiness in driving, and, finally, causes them to give up driving. The second conclusion related to availability of a parking lot can be justified, since more people who live in the suburbs, where availability of parking lots is higher, are seen in driver samples. Considering that urbanization is still in progress and that retired people enjoy driving on various occasions such as shopping and leisure, the number of elderly drivers who will quit driving does not increase. A public opinion poll revealed that many people think 60 years of age is the upper limit for driving

Characteristics

of older road users

399

%

B_ [RepI y of 56 - 60 yeers old dr ivers[ -Till ----28,

what am can you drive? Ti I I what age do ycu think old people can drive

I -60

Possible

?

1 -65

age of driving

,

I -70

71+

Fig. 8. Limiting age for driving.

(GAA 1992). The reply of older drivers to similar questions revealed that the age limit for themselves would go up, as is shown in Figure 8 (Nishiyama 1983). It seems older drivers strongly desire to drive as long as possible whether in the East or in the West (Alan and Laurence 1992). The above analyses are summarized as follows, Elderly drivers tend to drive with an intent to compensate for their recognized functional reductions, but are apt to drive with improper positioning or inflexible maneuvering caused by their reduced capability of recognition and judgment and their slowed driving operation. These driving characteristics of elderly drivers are believed to have connection with their characteristics shown in traffic accident statistics; that is, accidents at intersections with a complex shape and accidents involving being hit from the rear and the like. Moreover, the fact that reduced functions cannot be predictors for the choice of quitting driving indicates that some elderly drivers lack recognition of such reduction or do not want to quit driving, even if they recognize such reduction. Among elderly drivers who think of quitting driving someday but not now (“not-me syndrome”), problematic drivers can be found. The J curve is the evidence for the existence of such drivers. Today Japan is facing a rapid increase in elderly drivers, and continuation of the present system will surely invite an accelerated increase in traffic accidents caused by them. FEELINGS

OF ELDERLY

DRIVERS

Uneasy feelings experienced by elderly drivers during driving are reported in “Research report on

the driving practices of old drivers and their feelings during driving” (Vehicle Safety Driving Center 1984). The traffic situations that give them uneasy feelings are “passing oncoming vehicles on a narrow road, ” “changing directions,” “driving in a fast traffic flow” and “swift backward driving.” The percentage of the uneasy feeling about passing oncoming vehicles on a narrow road especially increases with age and this feeling coincides with the results of the previous section. Heavy traffic volume of pedestrians and invisibility of signals and signs are among the most frequent road conditions that cause them driving difficulties (Okamoto, Naemura, and Tatenaki 1982; Shimizu and Motoki 1983).

Table 3. Characteristics

in bicycle riding

a)Checking behind at the time of changing direction

b)Positioning

on a road

mj x2.17.4

> x’c!

. 0 . 01)=9 . 2

Y. MORIand M. MIZOHATA

400

Table 5. Analysis of factors related to walking speed

Table 4. Results of bicycle run trial Two figures in each cell are aean

Factor

value and standard deviation.

Partial corr.coef.

Spot

0.55

AL+

0.41

sex

0.12

LelLele

0.11

Pedestrian Note ;

N Number

of

@

Required

a

Deviation

from

et the @I Maximum *

Vehicle

subjects Distance

smay

on

stoppint

position

time

1% significance

for

of

left

directed turn

the straight against

young

troop

in moan

value

purpose

Time

zone

e

0.08

voluee

0.05 0.06 0.04

corr.

coef.

R

68.0

Number

of

samples

Crend

mean

value

(m/see)

1.33

Grand

std.

dev.

(m/set)

0.26

Note

CHARACTERISTICS OF ELDERLY BICYCLE RIDERS AND PEDESTRIANS First, the characteristics of elderly people during bicycle riding and walking, obtained from the specific surveys, will be described (Mizohata 199Oa, 199Ob). Table 3 shows the results of the survey of bicyclists. The age of the cyclists is collected through interview. Older cyclists are likely to neglect checking the traffic situation behind them when changing their directions and tend to sway towards the center of the road as much as 1 meter, compared to younger cyclists. They also traverse intersections or roads in an inappropriate manner. Table 4 shows the results of a bicycle run trial by three age groups. Age of the subjects is collected by interview. Older cyclists have larger sways, and their speed is 20% lower than that of younger cyclists. These can be attributed to reduced audition and judgment ability, muscle troubles typically represented by restricted rotation of the head, and reduced sense of equilibrium. In addition, no difference was observed in the data on sway among older cyclists with or without self-reliance in bicycle riding. This proves the lack of self-awareness of their reduced functions. The major factors influencing walking speed of pedestrians (excluding “observation spot” including slope), are age, sex, and luggage in hand from the view of the value of partial correlation coefficient shown in Table 5. Speed decreases sharply for people over 75 years (less than 1 m/set). A test was conducted, using one side of a national road. Older and younger persons to be tested were instructed to traverse along a pedestrian crosswalk laid on the sidewalk, judging from time headway of vehicles approaching the crosswalk. Table 6 shows the logistic regression for the rate of judging traversible chance (Y) and headway (t), classified by older and younger people. The headway for which the value of y becomes 50% shows no significant difference between older and

traffic

Trip

Multi. course

density

; *

1280

( men

/ square

meter)

younger people. Older people start their traverse almost at the same headway as do young people. However, the walking speed of older people is about 75% of that of young people in this test. Therefore, their allowance for safe traverse is less than that of young people. Moreover, older people tend to take several dangerous actions, such as low utilization of crosswalks, wandering, and intoxication (JTSEA 1987). These seem to be related to the rigidity of character seen among many older people (Neugarten 1977; Nagashima 1977). A fragile aged person often uses a wheelchair. Figure 9 illustrates the distribution of the trip length for older people who use handoperated wheelchairs or electric wheelchairs, including electric three-wheeled carts (MPT). Use of electric wheelchairs makes their trips longer by over 10 kilometers. This will be a matter of concern for traffic safety in view of our present road situations. Second, the statistically significant characteristics of traffic accidents, for elderly people, during bicycle riding and walking will be discussed (Mizohata 1986a). Figure 10 illustrates the characteristics of the place of accidents, for three age groups, during bicycle riding. The accident rate on sidewalks de-

Table 6. Results of logistic regression for traversible judgmental rate (Y) and time headway (t)

Young

Note;

Range of age

22-28~1~

No. of trials

IO

Old

70-8Oyr.v IO

401

Characteristics of older road users

Hard-operated wheelchair ( No. of samples 53 1

Electric

wheelchair

( No. of samples 48 )

One way distance Fig. 9. Distribution of trip length for older people who use wheelchairs

(MPT 1993).

something should be done about older people’s tendency to walk in the center of the road. Consequently, the reduced locomotion capabilities, the weakened functions for recognition and judgment, as well as the change of personality with advancing age, probably contribute to the occurrence of accidents in bicycle riding and walking. Ironically, older people who experience such accidents often have more healthy and active lives than older people who have not encountered them. It is pointed out that the rate of going out is inversely proportional to awareness of reduced functions and capabilities (Mukai 1992). Furthermore, the findings described above in conjunction with the characteristics of elderly drivers offer the possiblity of traffic

creases as age increases, but the accident rate on vehicle lanes and at road edges seems to increase. This coincides with the findings, shown in Table 3, that older bicyclists often sway and pay less attention to traffic behind them. Figure 11 shows the characteristics of the walking pattern of pedestrian accidents, divided into three age groups. Pedestrian accidents occur frequently at the time of traversing a road irrespective of age. However, such accidents involving elderly persons have happened at the latter half of the traverse, or at traverse soon before or after a vehicle. (Mizohata 1986a). As for walking against vehicles or in front of vehicles, the accident rate of older people is higher than that of young people, as is seen in this figure. This implies that

N=2548 0-59 years old 6&%69 years old over 76 years oil d x2=26.1

Sid&raIk

Uehiclk

lane Note

>

x2(6,0.01)=16.8

Road’ edge

Others

: Sidewalk includes the road for exclusive

use by bicycles.

Fig. 10. Places of trafEc accidents involving bicycles by age group.

402

Y. MORI and M. MIZOHATA

m

60-69

m

over

70 years old

>

22(6,0.01)=16.8

$=108.7

years old

40

0

While walking on a road

While traversing a road

While playing, working or stocxed

While walking On sidewalk or road edge

Fig. 11. Pattern of accidents involving pedestrians.

accidents among older people as follows: collision between older people who are walking or swaying on bicycles in the center of a road and older people who are driving cars in the outer lane or the left side of a road; accidents involving older people who are riding on carts and old people who are driving cars during twilight. CONCLUSIONS Elderly drivers try to maintain safe driving, backed by their high mental stability. They believe in their driving abilities and are convinced that driving cars supports their positive social activities. However, it cannot be denied that the several visual and cognitive functions related to mobility decrease with advancing age. Reduced functions do not constitute major reasons for quitting driving by elderly drivers. It is true that the number of elderly drivers who do not recognize or do not want to recognize such reductions is increasing. Increase in traffic accidents, caused by or involving older people, is now a social concern since Japan is approaching an aging society with the highest share of older population in the world. Limiting their social activities, with focus only on prevention of traffic accidents, would drive the joy of life from them and give a negative impact to their health maintenance or its enhancement. These conceivable results may bring other negative effects to society such as increase in welfare expenditures. If we look at the issues involving elderly people, based upon the discussion in this paper, we would inevitably reach the following conclusions. It is quite obvious that a systematic and comprehensive approach is necesasry to the issues, including improve-

ments of road structures and facilities, revision of educational systems for traffic safety and of the driving license renewal system. The basic principles for solving these issues should be built upon two concepts: the first concept is to improve the environment and systems so that such people can continue driving as long as possible; and the second concept is to set up a new social system in which quitting driving can be compensated for in some other way. The course of the former concept is in roads and vehicles that offer safer and less tiresome driving maneuvers. The major policies in road enhancement and improvement are basic design targetting ample allowance in time and space. Such designs should include: simplification of the complex intersections; enlargement of space at the left side of roads; sidewalks with higher quality for pedestrians, wheelchair users, and bicycle riders of advanced age; conof rest facilities; consideration of struction alternative transportation modes for older people who have quit driving or more aged people with health and welfare service; improvement of visibility of traffic signals and signs. The policy for developing suitable vehicles should target designs that allow easier driving not only to elderly people but also to everyone to compensate, if necessary, for reduced physical functions of drivers (Kobayashi 1992). The latter concept of setting up a new social system aims for an environment that urges older people with reduced functions to quit driving and which offers alternatives for them. This environment should include introduction of alternative transportation modes (Mori, Nitta, and Mizohata 1992); improvement of the educational system that teaches skills for safer driving; revision of the present driving license renewal system. The idea of restricting driv-

Characteristics

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