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Threat Avoidant Vigilance


“Research studies have examined “threat-avoidant” vigilant work, i.e., work that involves continuously maintaining a high level of vigilance in order to avoid disaster, such as loss of human life [56]. This is a feature of a number of occupations at high risk for CVD, e.g., truck drivers, air traffic controllers, and sea pilots. More recently, researchers have been investigating the health effects of employment insecurity and “downsizing” [60].” (Taken from: Schnall PL, Dobson M, Rosskam E, Editors Unhealthy Work: Causes, Consequences, Cures. Baywood Publishing, 2009.)

A cross-sectional study of San Francisco MUNI bus drivers conducted to evaluate the prevalence of hypertension in 1500 black and white male bus drivers (as compared to employed individuals in general) found that, after adjusting for age and race, hypertension rates for bus drivers were significantly greater than rates for each of the three comparison groups (individuals from a national survey, a local health survey and individuals undergoing baseline health examinations prior to employment as bus drivers).

Karen Belkic developed a Professional-Driver specific Occupational Stress Index in an effort to capture some of the effects of the work environment on drivers. She emphasizes that, “when the potential consequences of one’s actions can include disaster, work can become a threat-avoidant vigilant activity…. There is epidemiologic, human laboratory and experimental animal data that directly and indirectly links prolonged exposure to threat-avoidant vigilant activity with adverse cardiovascular outcomes, including cardiac electrical instability and even sudden cardiac death (Corley 1977, Lown 1990, Menotti 1985, Murphy 1991, Suurnakki 1987, Theorell 1993).” 

The OSI Questionnaire for professional drivers is about half the length of the General OSI, and the questions are very concrete and germane to this occupational group.

Below are a few select items from the OSI for professional drivers:

16. Do you always have at least one break during your work day?   Yes   No

If yes, how many breaks do you usually have?_______
How long is your usual break?___________

17. The times at which you drive / your work schedule: 
*Do you have a regular work schedule?   Yes   No 
*If yes, when do you begin work? _____________ End work:________________

* Do you drive the split shift (early morning and afternoon rush hours)
   a. Yes, I constantly work the split shift
   b. Sometimes
   c. Rarely or never

*Do you drive in the dark/at night ?
   a. No, I work (drive) only during the daylight hours.
   b. Yes, I drive in the city at night, and/or when it’s dark.
   c. Yes, I drive inter-city (long routes) at night, and/or when it’s dark.
(If no, continue with question 18)

*If you drive on the job at night, 
Are the roads well lit?   Yes   No
Are the roads divided according to the direction of traffic?   Yes   No

*Do you drive after midnight (third/night shift)?   Yes   No
If yes, do you drive the night shift:
   a. Constantly
   b. On a rotating basis (describe please how this rotates:______________)

 19. Do you perform heavy lifting at work?

   a. Yes, often times during the day lift 50 kg ( 110 lbs), or more. 
   b. Yes, I lift from 20 to 50 kg loads (44 – 110 lbs) during my usual work day.
   c. Yes, I lift up to 20 kg (44 lbs) during my usual work day.
   d. No, I rarely or never lift anything heavy during work.

 20. What are the physical conditions like in your vehicle cabin?

   a. I have good shock absorbers and isolation. I don’t usually feel much vibration nor gases/fumes.
   b. I have poor shock absorbers, but good isolation. I feel vibration but not much gases/fumes
   c. I have good shock absorbers but poor isolation. I don’t usually feel much vibration but I do feel gases/fumes because the isolation is poor.
   d. I have poor shock absorbers and poor isolation. I feel vibration and also gases/fumes.

 22. Do you drive under specially hazardous conditions (check all answers that apply)

   a. Yes, I carry flammable/explosive material in my vehicle.
   b. Yes, I drive along winding, narrow roads
   c. Yes, I face threat of violence from passengers
   d. Yes, for another reason(s): ______________________________________________
   e. No, I face ordinary traffic conditions, but no special hazards.

 23. Have you even had an accident or been injured (including assault) at work?

   a. No
   b. Yes, only of a minor nature
   c. Yes, I have had one or more serious accidents or have suffered serious physical harm at work:

Please briefly describe all serious accidents or injuries 


56. Belkic, K., P. A. Landsbergis, P. Schnall, et al., Psychosocial Factors: Review of the Empirical Data among Men, in The Workplace and Cardiovascular Disease Occu- pational Medicine: State of the Art Reviews, Schnall, P., K. Belkic, P. A. Landsbergis, and D. Baker (eds.), Hanley and Belfus, Philadelphia, PA, pp. 24-46, 2000.

60. Vahtera, J., M. Kivimaki, J. Pentti, et al., Organisational Downsizing, Sickness Absence, and Mortality: 10-Town Prospective Cohort Study, British Medical Journal, 328:7439, p. 555, 2004.

A Day in the Life of a San Francisco Municipal Trolley Car Driver:


Burden and consequences upon the human operator Karen Belkic, M.D., PhD, Peter Schnall, M.D., MPH

Operating a motor vehicle in the city is an activity not unfamiliar to most of us. Yet, the toll which this activity takes upon the human nervous system and target organs is, to say the least, under-appreciated in daily life. Try to imagine that rather than at most a couple of other known persons sitting in one’s car during this undertaking, one were responsible for transporting thousands each day via narrow, hilly streets, facing innumerable obstacles and under inexorable pressure to keep to a strict schedule, and that the slightest accident could result in injury to a passenger and might even put one’s job in question. And also imagine that rather than at most a few hours of this activity per day, this consumed eight or even more hours daily for five or more days in a row. These and many, many more stressors comprise the everyday experience of the San Francisco urban transport operators, who encounter problems specific to their city, but also in many ways, exemplify the difficulties which transit operators face in just about any metropolitan center which comes to mind.

On July 10, a group of us from the California Focused Study Group, had the opportunity of gaining a deeper insight into some of these difficulties and perils, during a “narrated” ride along San Francisco’s Line 22. We were privileged to have a veteran transit operator talk us through the mental processes which were taking place while the actual driver proceeded to perform the job. This perspective was complemented by Dr. Birgit Greiner’s observational methods to measure the barriers, obstacles, restrictive time binding and other stressors of urban transport operators.

Danger-Threat of Violence

While varying in degree from one urban center to another, danger and threat of violence is a common and major stressor for this occupational group. The transit operator is vulnerable to violent attack at any moment; there are frequent reports of the driver being robbed at knife or gunpoint. The enormous social problems of urban society are often manifested in hostile acts directed against the transit operator. Carrying cash and transfers increases vulnerability.

Besides physical danger, frustrated persons often verbally vent their rage upon the transport operator. They may complain about the bad conditions in the vehicle itself, about which the driver is only more than well aware. The urban mass transit operator has, de facto, to be a kind of psychologist-to anticipate and handle all kinds of people and their troubles, and to devise coping strategies to minimize the disruption from these complaints.

On the other hand, interaction with the public is not only one of the major tasks of the mass transit driver, it also is frequently a source of satisfaction and gratification. Thus, suggestions for constructing compartments to separate the operator from the public in numerous settings including San Francisco, have met almost universally with opposition. The sentiments expressed were that this would feel like “cage” and create a sense of isolation and alienation. One, more human way out of this dilemma has been suggested by Drs. Kompier and DiMartino, i.e. that on certain lines, high-risk transport calls for two transport professionals on the line, instead of one. This proposal has been resisted by the companies because, they say, it would cost too much.

Time pressure
Inexorable time pressure is the modus vivendi of the urban transport operator. One’s life becomes governed by the clock, and life is measured in time units of minutes. Waking for the morning rush hour passengers, often means rising at very early hours, sometimes two or three A.M. Scrupulously punctual drivers, fearful of not hearing the alarm, have reported to sleep lightly or not at all in anticipation of this early, strictly-defined awakening time. Running late, often not the fault of the driver, will compromise or eliminate the already short rest break which is scheduled usually at the end of the line. If the schedule is more severely compromised, some other kind of punitive measure may be taken. The driver is continuously pressing to catch-up with the schedule.

Dr. Greiner calculated that objective barriers took at least thirty extra minutes for nearly half of the four-hour work segments which she and her colleagues studied. The late Dr. Bertil Gardell eloquently described the fundamental conflict faced by urban mass transit operators: keeping on schedule versus providing to the immediate, specific needs of the public. This means not only answering questions, but also many other services, most notably, taking the extra time to accommodate the disabled and elderly.

Vigilance and avoiding accidents: Doubly burdensome for professional drivers
Even under the most ideal of circumstances, all driving requires high level vigilance to avoid accidents. The driver must continuously follow a barrage of incoming signals, to which he or she must be prepared to rapidly respond, whereby a momentary lapse of attention, or even a seemingly slight error or delayed response could have potentially disastrous consequences. For the urban transit operator this burden is much greater than for an amateur driver. For example, he or she must watch right-left-right-left before making any move, whereas the amateur driver usually makes just three visual direction shifts. An eye must be kept open for oncoming and exiting passengers and anyone at the side of the curb. There is a need to watch on the right far more than for amateur drivers. This can be one of the contributing factors to the high rate of neck and other spinal pain among professional drivers, which has been shown to be related to number of years in the occupation (witness the previously mentioned worn-down right side of the seat).

Furthermore, in situations for which an amateur driver would brake (or quickly change lanes or otherwise make some rapid maneuver), the urban mass transit operator must think about the fact that people are standing, there are frail passengers, or someone may be unsteady on his or her feet, and must try to maneuver accordingly. These dilemmas are obviously not always resolvable. If someone falls inside the vehicle, the transit operator is held liable. It should be noted that any one can stagger onto the bus, be unstable on his feet, etc. requiring yet extra vigilance for the transit operator. The biggest worry is always about an accident, whether big or small. Even a seemingly trivial accident may result in injuries to passengers.

Don’t they just get “used to it”?
An easy assumption to make would be that with experience and time on the job, a city transit operator will adapt to these conditions, difficult as they may be. And it is true that the acquired coping skills and knowledge of a seasoned professional driver are irreplaceably valuable assets, without which it would be practically impossible to continue in this line of work. There is a high turnover rate among urban mass transit operators, such that those who stay on the job for ten or more years are a highly selected group.

However, a heavy price accompanies these years on the job. The very skills which get the driver through a working day are, in fact, a quiet displacement of the burden onto his or her target organs: the heart, the blood vessels, the gastrointestinal tract, the musculoskeletal system. It has been shown both in laboratory simulation and field studies that the experienced drivers who silently cope and seemingly automatically handle the continuous barrage of potential dangers and who toughly deny how difficult this work is, are those who show the most dramatic blood pressure and electrocardiographic responses to these threatening stimuli of the traffic environment. Reviews of the literature show that professional drivers are second to none as an occupational group at risk for hypertension and ischemic heart disease and that these diseases occur at a relatively young age. Several studies of heart attack patients under the age of forty report a marked overrepresentation of professional drivers, up to 40%, in some series. The published papers showing a high risk among this occupational group for cardiovascular and cerebrovascular disease, musculoskeletal disorders and/or peptic ulcer disease come from various parts of the world: from Europe, the U.S., Latin America, East Asia and the Indian subcontinent. A strong relation between number of years on the job and/or number of daily hours behind the wheel have been found in many of these studies.

The terrible human toll taken by these diseases, coming at an early adult age, also translates into enormous economic costs: absenteeism, disability and early retirement. It is unusual for a mass transit operator to retire at term in any city. In the Netherlands, for example, the average age of retirement for city bus drivers is 48 and is usually disability-based, with only 12% working until the normal retirement age of 60.



July 2000 ( Please note for each question there is first a short answer, followed by a fairly detailed explanation.)

1. Neurocardiac mechanisms of heart disease risk among professional drivers

a) Definition of Professional Drivers and what do they all have in common?
We define professional drivers as those workers whose main job is to operate a motor vehicle in traffic conditions. This includes chauffeurs, bus, truck, tram, trolley, taxi and ambulance drivers.

While each of these groups has its own distinguishing characteristics and problems, they share common features that are critically important stressors. Namely, all professional drivers perform what we call “threat-avoidant vigilant activity” where they must maintain a high level of attention, in order to follow a large number of information sources simultaneously to which they must rapidly respond, whereby a momentary lapse or wrong decision can have serious, potentially fatal consequences. The burden is heaviest upon their visual systems, but also they must be keep their hearing and somatosensory systems on alert. This work is performed while seated in a relatively fixed position in a confined space.

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