Increased Perception of Strain and Related Cognitive Functions in Drivers with Aging

Abstract

With age, physical and cognitive functions generally tend to decline. However, with appropriate measures, it is possible for older train drivers to continue their duties safely and confidently. The first step in this study was to obtain fundamental data to investigate measures needed to enable older drivers to continue driving. Based on a survey result, we identified tasks for which perceived strain increases with age. Furthermore, it was revealed that the increase in perceived strain of these tasks is associated with age-related declines in attention, vison, decision making and reaction time.

1. Introduction

In Japan, labor shortages due to a declining birth rate and aging population are accelerating. Securing enough train drivers is therefore one of the most important issues for railway operators. One possible solution to this problem is an extension of the retirement age for drivers. To achieve this, it is necessary to identify the tasks for which the strain increases (physical and mental) with age, and to support older drivers. However, there has been no comprehensive study on the effects of aging on driver tasks. Therefore, we first conducted a survey to identify the tasks that drivers find more difficult with age. Next, we conducted a survey to investigate the functional changes with age that affect the increase in perceived strain. Older drivers and young drivers in this study were defined as follows.

Older driver: over 55 years old.

Young driver: more than 3 years of driving experience and under 39 years old.

2. Identification of tasks for which strain is perceived to increase with age

Two surveys were carried out to identify which tasks drivers perceived as more strenuous with age. First, we conducted a survey of perceived driver strain for each task and identified tasks which were perceived as more strenuous by older drivers compared to young drivers. This was followed by interviews to gain deeper understanding of what older drivers considered more strenuous than younger drivers, in the tasks identified during the first survey.

2.1 Questionnaire on perceived strenuousness of driver tasks

Drivers from two railway operators participated in the survey. The number and average age of the participants is shown in Table 1. Participants responded to questions on a 5 - point scale (1: Not difficult at all to 5: Very difficult) on how difficult they perceived each task to be. The tasks to be evaluated were selected with reference to a previous study that organized the train driver's task. The questionnaire surveyed ordinary tasks performed by drivers and excluded tasks which would be carried out in abnormal situations. The questionnaire included 84 tasks for rail operator A and 83 for rail operator B.

Table 1　The number and mean age of the participants in the questionnaire survey

Railway operator	Older driver	Young driver
A	37 Meanage = 61.5 SD = 1.32	56 Meanage = 31.4 SD = 2.93
B	35 Meanage = 61.7 SD = 1.50	35 Meanage = 32.5 SD = 2.82

We conducted a t-test to compare the difference between the means of older and younger driver scores. The results showed that the perceived level of strenuousness for 27 out of 84 tasks was statistically higher for older drivers than younger drivers at railway operator A. At railway operator B, the perceived level of strenuousness was statistically higher among older drivers for 34 out of 83 tasks (5% level of significance).

2.2 Follow-up interviews to understand strenuousness of tasks

From the questionnaire, it was found that many tasks were perceived by older drivers to be more strenuous. However, not all the strain can be attributed to aging. Therefore, to identify the tasks where perceived strain may have increased with aging, we conducted semi-structured interviews to understand what exactly was perceived as strenuous in the tasks rated as more strenuous by older drivers, compared to younger drivers. We asked participants about how hard the tasks are, in terms of physical, mental, and other aspects, and added questions depending on participants' answers. The number and mean age of the participants is shown in Table 2

Table 2　The number and mean age of the participants in the interview survey

Railway operator	Older driver	Young driver
A	5 Meanage = 60.2 SD = 0.45	5 Meanage = 29.8 SD = 2.22
B	4 Meanage = 61.5 SD = 1.29	6 Meanage = 30.7 SD = 1.63

2.3 Results of perceived strenuousness of driver tasks

The average rating of perceived strenuousness of each task is shown in Fig. 1. Tasks in red font are those for which the perceived strain increases with age.

Fig. 1　The driver's tasks for which the perceived strain increases with age

Several older drivers answered that the perceived strain of some tasks had increased due to changes in the working environment, rules, and procedures. The increase in the perceived strain of these tasks was not considered to be due to aging. Furthermore, among the tasks where older drivers rated the perceived strain higher than younger drivers, some had an average rating which was low for both age groups. Therefore, tasks which had a mean score of less than 3.0 and which were described by all the drivers in interviews as “not hard” were categorized as tasks with no increase in the perception of strain. On the other hand, even if a task obtained a score of 3 or less, if many older drivers mentioned in interviews that the strain increased with age, it was categorized as a task for which perceived strain increases with aging.

3. Evaluation of age-related functional changes associated with increased perceived strain

This chapter describes an evaluation conducted by experts to estimate the impact of age-related functional changes on increased perceived strain.

3.1 Evaluation items

During the interviews to elucidate specific strain, it became clear that some of the evaluation items (train driver's tasks) in the questionnaire survey were not appropriate for expert evaluation. For such items, we revised them. The final set of evaluation items is shown in Table 3.

Table 3　Evaluation Items

No.	Work category	Evaluation items to be checked
1	Inspection before departure from depot	Walk to the train with their luggage
2		Check train number from the ground
3	Signal check	Check signal (general)
4		Check signal while high-speed driving
5		Check signal during dark hours
6		Pointing and calling out to the signals in mainline operation
7		Pointing and calling out to the objects other than signal in mainline operation
8	Check timetable and instrument panel	Check timetable
9		Check watch
10		Check instrument panel
11		Check speed limits for entering and exiting switches listed in timetable
12	Confirmation of course of operation	Check signal and platform when entering a non-stop station
13	Handling of arrival and departure (one-man)	Braking after stopping (prevention of rolling)
14		Check platform and opening/closing doors
15		Check departure signal before departure
16		Check departure time
17		Handle ATS chime (ringing noise and the procedure for turning off)
18		Check departure signal when departing
19		Check speed limit at departure
20		Check the mirrors on the platform when departing
21		Pressing public announcement button after departure and before arrival
22	Others	High-speed driving
23		Operation when there are delays
24		Tablet implementation (e.g., new devices)
25		Pointing check while working
26		Calling check while working

3.2 Expert evaluation

The functions to be evaluated (Table 4) were selected on the basis of previous studies on age-related changes in various functions [1, 2, 3, 4, 5], the opinions of managers who supervise drivers, the responses of older drivers from the interviews, and the tests conducted for older drivers when they renew their car driving licenses in Japan.

Table 4　Functions targeted by functional assessment in relation to increased strain

Function		Explanation of each function.
Vision	Dynamic visual acuity	Vision to see moving objects
	Night vision	Vision to see things in the dark
	Accommodation	Ability to focus on an object
	Color discrimination	Distinguishing between colors
	Field of view	Range of vision that can be seen without the movement of eyes or head
	Glare vision	Ability to see clearly in bright or glaring light
	Dark adaptation	Time it takes to become visible when suddenly moving from a bright place to a dark place
Hearing	Recruitment Hearing	A phenomenon in which soft sounds are hard to hear and loud sounds are loud.
	Discrimination of sound	Distinguish necessary sounds in the presence of multiple sounds and noises
Decision-making		Make appropriate decisions based on the situation.
Memory	Working memory	Temporarily store and process information required for a task or operation.
	Knowledge	Knowledge obtained through training, experience, etc.
	Learning ability	Ability to learn new things
Attention	Divided attention	Divide attention to multiple targets simultaneously
	Switch attention	Shift attention from one to another in succession
	Inhibition	Suppress attention to irrelevant things when there is something to focus on
Reaction time		Time between noticing things and reacting to them
Speediness		Perform a series of movements quickly

A total of 22 experts with sufficient knowledge of train driver tasks participated in expert evaluations from railway operators A and B (A: 10, Mean_age = 37.5, SD = 5.42; B: 12, Mean_age = 42.8, SD = 4.75). They evaluated the degree to which each function (Table 4) was related to each task (Table 3) on a 5 - point scale (1: not related at all ~ 5: highly related).

3.3 Results of expert evaluation

The results are shown in Table 5. Yellow cells in the table indicate an average rating of 3.5 or higher, and red cells indicate 4.0 or higher. These results indicate that the functions corresponding to vision, judgment, attention, and reaction time are particularly related to the tasks for which the perceived strain increases with age.

Table 5　Expert evaluation results

Vision was particularly relevant to tasks that falls into the categories of “Signal check,” “Check timetable and instrument panel.” It was also relevant for “Check signal and platform when entering a non-stop station,” “Check one-man mirror at departure” and “High-speed driving.” These tasks are confirmation procedures using eyes and are susceptible to the decline in vison with aging [3].

The judgment was particularly relevant to “Check signal while high-speed driving,” “Check signal during dark hours,” “Check signal and platform when entering a non-stop station,” “Check departure signal when departing,” “Check the mirrors on the platform when departing,” “High-speed driving” and “Operation under delay.” In the interview survey, many participants answered that they are particularly careful and feel a high strain in these tasks, since a misjudgment in these tasks can lead to a serious accident. Many older drivers who are aware of the decline in their judgment ability considered to feel more strain.

The attention was particularly relevant to the tasks that falls into the categories of “Signal check.” It was also relevant to “Check signal and platform when entering a non-stop station,” “Check platform and open/close the door,” “Check departure signal when departing,” “Check one-man mirror at departure,” “High-speed driving,” “Operation under delay” and “Pointing check throughout entire job.” The attention is one of the functions that is strongly affected by aging [4, 5]. These tasks, which involve checking multiple objects simultaneously or frequently performing a series of checking actions, are severely affected by aging.

Reaction time was particularly relevant to tasks in the “Signal check” category. It was also relevant to “Check signal and platform when entering a non-stop station,” “Check one-man mirror at departure” and “High-speed driving.” Reaction time increases with age. It is particularly important to react quickly when an anomaly is detected when checking a signal or checking a platform or when driving at high-speed. Older drivers, who are aware of a delay in their reaction time, are likely to find these tasks more stressful.

4. Conclusions

From the train driver surveys, we identified tasks for which perceived strain increases with age. We also confirmed that age-related changes in vision, decision-making, attention, and reaction time were responsible for the increased perception of strain. Even if some functions decline with age, taking measures such as being aware of these declines and checking more carefully than when you are younger could allow older drivers to continue to drive safely.

In the medical field, it has been confirmed that cognitive training for older people has been shown to improve attention and other functions [6, 7]. If cognitive training for train drivers can be developed, it may be possible to reduce the strain on older drivers. In the future, we aim to develop specific support measures based on the age-related driver stress or burden and related functions identified in this study.

References

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• [4]  Rogers, W., “Attention and aging,” Cognitive aging: A primer, New York, Psychology Press, pp. 57-73, 2000.
• [5]  Zacks, R., & Hasher, L., “Cognitive gerontology and attentional inhibition: A reply to Burke and McDowd,” Journal of Gerontology, Series B, Psychological Science and Social Science, 52 (6), pp. 274-283, 1997.
• [6]  Karlene, B., Daniel, B. B., Karin, F. H., Jared, B. J., Mary, D. L., Michael, M., John, N. M., George, W. R., David, M. S., Sharon, L. T., Frederick, W. U., & Sherry, L. W., “Effects of cognitive training intervention with older adults: A randomized control trial,” The Journal of American Medical Association, 288, 18, pp. 2271-2281, 2002.
• [7]  Nouchi, R., Taki, Y., Takeuchi, H., Nozawa, T., Sekiguchi, A., Kawashima, R., “Reading Aloud and Solving Simple Arithmetic Calculation Intervention (Learning Therapy) Improves Inhibition, Verbal Episodic Memory, Focus Attention and Processing Speed in Healthy Older Frontiers in Human,” Neuroscience, 2016.

Authors

	Ryo NAKAMURA, Ph.D. Senior Researcher, Safety Psychology Laboratory, Human Science Division Research Areas: Cognitive Psychology, Brain Science, Aging
	Ayanori SATO, Doctor of Psychology Senior Researcher, Safety Psychology Laboratory, Human Science Division Research Areas: Cognitive Psychology, Memory, Human Error
	Takayuki MASUDA, Ph.D. Senior Researcher, Safety Psychology Laboratory, Human Science Division Research Areas: Traffic Psychology
	Yasuhiro KITAMURA. Technical Manager, Senior Researcher, Safety Psychology Laboratory, Human Science Division Research Areas: Psychology, Human Error, Decision Making
	Munendo FUJIMICHI, Ph.D. Researcher, Safety Psychology Laboratory, Human Science Division Research Areas: Cognitive Psychology, Evacuation Behavior
	Ayano SAITO, Ph.D. Senior Chief Researcher, Head of Ergonomic Laboratory, Human Science Division Research Areas: Ergonomics