Union offers advice on excessive cab temperatures

07 January 2005

ASLEF has offered its members advice on the symptoms of heat stress, and their rights as individuals if they feel themselves endangered as a result of excessive heat.

The advice is as follows:

Guidance is issued with this circular to members and safety representatives to help identify symptoms of heat stress and to outline remedial measures which should be taken.

Employers have a general duty under the Health and Safety at Work Act 1974 to provide a healthy and safe workplace. They are therefore required to take reasonable steps to prevent heat stress. In this respect heat stress is no different to any other risk to safety.

Where arrangements outlined in ¡§Heat Stress: Safety Representatives¡¦ Check List¡¨ are not in place, safety representatives should raise the matter with an appropriate manager. Where the matter cannot be resolved at local level, it should be referred to the appropriate next level in the safety machinery.

Below is a Railway Safety Briefing from January 2002.

Members should be advised that some of the symptoms of heat related illness, which include poor work performance, fatigue, giddiness, confusion, loss of concentration and mental confusion, may leave members unsuitable to drive trains.

Advice on serious and imminent danger

Under the Employment Rights Act 1996, as amended, employees have the right not to be dismissed, selected for redundancy or subjected to any detriment on the following grounds: -

¡P The employee left, or proposed to leave, or (while the danger persisted) refused to return to his or her place of work, or any dangerous part of it, in circumstances of danger which he or she reasonably believed to be serious and imminent, and which the employee could not reasonably have been expected to avert

¡P The employee took, or proposed to take ¡§appropriate steps¡¨ to protect himself or herself or other persons in circumstances of danger which he or she reasonably believed to be serious and imminent.

This is explained in ¡§Harvey on Industrial Relations and Employment Law¡¨ that:

¡§¡K(in) the case of the employee who believes himself to be in serious and imminent danger and who on that account quits work. The employee¡¦s belief must be both genuine and reasonable. If he cannot reasonably avert the danger, then he is entitled betake himself out of harms way. The employer must not victimise him for leaving the area of danger, or for proposing to leave it, or for refusing to return while the danger lasted.¡¨ 

Case law has established that an employee¡¦s reasonable concerns may also cover serious and imminent danger affecting members of the public.

Further, in a recent case, union members working for LUL who refused to work during the fire-fighters dispute, and who were not paid, had a hearing listed for their application that any deduction of pay was unlawful.

There were two arguments. One was based on the law cited above enabling anyone to absent themselves from the workplace when there is a serious and imminent danger and a significant risk, and this does not amount to secondary industrial action.

The other was based on a breach of contract argument relating to the implied term that the employer will provide for the health and safety of staff (see e.g. Johnson v Bloomsbury Health Authority).

LUL settled out of court and agreed to pay the applicants all the money they had deducted. 

Advice to Members

Members are advised that ASLEF believes that circumstances may arise in which our members and the public are in ¡§serious and imminent danger¡¨, due to the possible physical symptoms arising from heat related illnesses while driving trains in hot weather.

If members have a reasonable belief they and/or the public are in ¡§serious and imminent danger¡¨, because of this, they are referred to the legal position expressed above.

Members should inform Supervisors of their specific concerns and should state clearly what appropriate steps they reasonably intend to take to protect themselves and the general public to avoid or reduce the danger. 

If members¡¦ are in doubt they are advised to contact their District Secretary.

Please bring the contents of this circular to the attention of your members.

Yours fraternally,

Keith Norman

Acting General Secretary


Heat Stress

Medical Effects of Heat

High temperatures can defeat the body¡¦s ability to cool itself. If this happens, internal body temperature then rises dramatically and drastically. Effects from heat range from discomfort and dehydration to heat stress, heat stroke, kidney damage and even death.


The World Health Organisation recommends 75„aF and 24„aC as a maximum air temperature for comfortable working. Above this temperature, people are more liable to have accidents as they are less alert.


Symptoms are headaches, tiredness and cramps. Fluid lost through sweating must be replaced. There should be access to cool fresh drinking water and sufficient breaks. Salt may be made available but only taken in moderation.

Heat Rash

Also known as prickly heat, may occur in a hot and humid environment when sweat is not easily removed from the surface of the skin by evaporation. When extensive or complicated by infection, heat rash can be so uncomfortable that it inhibits sleep and impedes a worker¡¦s performance or even results in temporary or total disability. It can be prevented by resting in a cool place and allowing skin to dry.

Heat Cramps

Painful spasms of the muscles, are caused when a worker drinks large quantities of water but fail to replace their body¡¦s salt loss. Tired muscles ¡V those used for performing the work ¡V are usually the ones susceptible to cramps. Cramps may occur during or after working hours and may be relieved by taking liquids by mouth or saline solutions intravenously for quicker relief, if medically determined to be required.

Heat Exhaustion

Results from the loss of fluid through sweating when a worker has not replaced enough fluids by drinking or taken in enough salt or both. The worker with heat exhaustion still sweats but experiences extreme weakness, fatigue, giddiness, nausea or headache. The skin is clammy and moist, the complexion may be pale or flushed and the body temperature is normal or slightly higher. Treatment is usually simple. The victim should rest in a cool place and drink an electrolyte solution (a beverage used by athletes to quickly restore potassium, calcium and magnesium salts). Severe cases involving victims who vomit or lose consciousness may require longer treatment under medical supervision.

Heat Fatigue

Resulting from prolonged heat exposure, causes a decline in coordination, alertness, and performance. With so much blood going to the periphery of the body, less is available for muscles. Strength drops and fatigue kicks in sooner that otherwise. Accidents are more likely to happen. For example, accident rates for heavy machine operators double when they work in hot environments.

Heat Stress

Symptoms are clammy skin, light headedness, slurred speech, rapid pulse rate, fatigue, confusion, fainting, nausea, short temper and loss of concentration. Victims should be removed to a cooler area and given liquid.

Heat Stroke

Symptoms are a staggering walk, hot skin and raised body temperature (though the victim may feel chilly), incoherence, mental confusion, convulsions and unconsciousness. This can lead to long term illness and even death. Victims should receive immediate medical attention. Victims of heat stroke will die unless treated promptly. While waiting for medical help, the victim must be removed to a cool area and his or her clothing soaked with cool water. He or she should be fanned vigorously to increase cooling. Prompt first aid can prevent permanent injury to the brain and other vital organs. 

Heat Stress:  Safety Representatives¡¦ Check List

Water Dispensers

Cool drinking water should be available at all booking-on and PN points.

Where this is not the case, safety representatives should make representations to their management.

Water Containers

Personal water containers or bottles should be available for use when in the cab. These may be replenished as and when required at booking-on and PN points.

Where this is not the case, safety representatives should make representations to their management.


Uniforms now vary from operator to operator. Full uniform may not be appropriate during periods of hot weather. Drivers should be permitted to wear clothing appropriate to the cab temperature.

Where the uniform policy is too restrictive, safety representatives should make representations to their management.

Effects of Excessive Heat

Where traincrew suffer the effects of excessive heat in the cab, arrangements should be in place for an appropriate manager to be contacted and the member of traincrew to be relieved.

Traincrew must in no way feel intimidated into not reporting their condition. Ignoring dehydration, heat stress and heat stroke is not only harmful to health but endangers the safety of the train.


Railway Safety January 2002

Working in Heat

The December 2001 issue of the CIRAS journal reported that there had been concern for the high cab temperatures experienced during the summer months. The major concern was the risk of heat exhaustion to the driver. It was suggested that there was a lack of ventilation in some cabs and insufficient cooling in others. There are a number of steps a driver can take to avoid the effects of heat. 

Below is a brief explanation of how our body attempts to cool itself and some suggestions to aid this natural cooling system. 

Why do we sweat?

It is one of our body¡¦s natural methods of cooling. Sweat is released through the pores of the skin and evaporates, removing heat as part of the process.

What is dehydration?

Dehydration is when our water intake does not balance the water loss and therefore creates a deficit in our system. 

If you are thirsty it is too late! You are already dehydrated.

Thirst is an inadequate indicator of your body needing fluid. A simple way of determining whether you are dehydrated is by checking the colour of your urine. If your urine is clear, you are hydrated but that does not mean you should stop taking on fluid - especially if the environmental conditions of your cab have not changed or even increased in temperature. 

There are also a few other indicators of dehydration: 

¡P sunken eyes 

¡P wrinkled skin, which may lack its normal elasticity and sag back into position slowly when pinched into a fold 

¡P fatigue 

¡P dizziness 

¡P increased breathing

¡P headache. 

How will I be affected if I am dehydrated?

Studies have shown that prolonged exposure to cab temperatures above 18¢XC result in increased percentage of error rate and response time. It is thought that the Temperature is not the direct reason for the reduction in performance, but one that causes increased loss of water, leading to dehydration. The effects of dehydration are the most likely cause for a driver¡¦s increased error rate and response time. 

Here are some guidelines to avoid dehydration:

¡P Avoid diuretic drinks such as coffee and tea. Alternatively, drinks such as water and fruit juice mixed with water are ideal for maintaining your hydration.

¡P If exposed to prolonged periods of heat it is advised to replace lost fluid by drinking between 100 to 150 ml water several times per hour.

¡P Wear clothing, which is thin, lightweight, quick drying, and permeable to water vapour and to air (ie cotton).

¡P Wear loose fitting garments.

¡P Avoid consuming a large meal, digesting a large amount of food will increase the body¡¦s core temperature.

Normal deep-body temperature is taken as 36.8oC. This is subject to small variations due to the time of day ¡V body temperature normally rises during the late afternoon and falls at night. Body temperature also increases slightly after a meal. The temperature of the skin surface is somewhat lower, around 33-34oC, and varies across the body. Generally the peripheral parts of the body, ie arms and legs are cooler than the torso. Physical work, hot environments and excessive clothing insulation have a more profound effect on body temperature.

Causes of heat strain and the resulting symptoms

Inappropriate combinations of physical work, protective clothing and thermal environment can result in a steadily increasing body temperature. If left unchecked the person is in danger of becoming a heat casualty. Prior to this, the person will experience a variety of symptoms. Initially these symptoms are mainly neuromuscular and psychological ¡V feelings of fatigue, apathy, decreasing motivation and finally hallucination. Irrecoverable biochemical changes occur at deep-body temperatures above 40oC. Therefore, for most practical workplace situations a limit of 37.5oC is recommended.

¡¥Prescriptive Zone¡¦

Numerous studies have shown that the deep-body temperature can be maintained over a wide range of environmental conditions. This ¡¥Prescriptive Zone¡¦ is so called because it has been used to prescribe safe working environments for industry. Within the Prescriptive Zone, deep-body temperature is simply a function of the rate at which physical work is performed. At environmental temperatures above the Prescriptive Zone, however, the resulting deep-body temperature is also a function of the environmental temperature. This is shown schematically in Figure 1.

Figure 1: Schematic diagram showing effect of environmental temperature on deep-body temperature

The Prescriptive Zone can be used to set an absolute upper temperature limit for the environment, given knowledge of the other key variables: work rate and clothing. However, this makes no comment on whether the environment will result in thermal comfort. The environmental temperature required for thermal comfort will, almost by definition, be lower than that which can be physically tolerated.

In summary, it is always preferable to be able to control the thermal environment within comfortable limits. Where this is not possible, drivers need to pay particular attention to physical warning signs in order to protect themselves from the effects of heat.

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