Where a risk assessment has identified a risk the first consideration is the risk itself, how severe is the risk, what is the likelihood of an incident and the number of people who are exposed to the risk, this is set at the cost both in time and financial terms, the effort and materials required to put control measures in place to reduce the risk.
For example, where there is a high risk that a large number of people are exposed to it would be deemed reasonably practicable for the employer to go to substantial expense and time to reduce the risk. Where the risk is deemed to be very low it would not be reasonably practicable to ask the employer to spend a large amount of money putting control measures in place to reduce it.
It may seem obvious to everybody that spending a few pounds to prevent a serious injury to a large number of people is reasonably practicable and spending thousands putting in control measures to reduce the risk of someone cutting their finger is not reasonably practicable, however there are no set rules and what is reasonably practicable will vary from one business to another, in most situations where a dispute arises the decision as to whether or not it was reasonably practicable will be made in a court of law. It is important to remember that the judgement is an objective one based on the health risks and not the size or financial position of the employer.