As noted above, there are numerous situations that are likely to result in fatigue. Six situations with the highest risk have been identified as Key Risk Factors. Five others are identified as Additional Risk Factors. List of Key Risk Factors: (1) The total length of the work shift exceeding 14-16 hours; (2) Continuous hours of wakefulness beyond 19 hours; (3) Working between the hours of 0000 and 0600; (4) Obtaining less than six hours of continuous sleep in a 24-hour period; (5) Break times that do not permit reasonable recuperative times (<8 hrs); and (6) Continuous work beyond 64 hours in a seven-day period. Additional Risk Factors: (a) Less than two consecutive nights of recuperative sleep; (b) Continuous work for over five hours without at least a 30-minute break; (c) Undiagnosed or untreated medical conditions (eg. sleep apnea) that may affect fatigue; (d) Differences in ability to sleep and respond to conditions (eg. age, hardiness); and (e) Quality of sleep. The six Key Risk Factors are listed below with suggested countermeasure strategies that might be included in your FMP. note: Some content in each of the following sections is repeated in order to ensure adequate and complete coverage of important strategies to address each Key Risk Factor. About the Graphs: Several of the Key Risk Factor strategies were examined for their overall effectiveness in reducing fatigue. The impact of the strategy can be determined by looking at when and how far below the recommended fatigue threshold the line plotted in the graph drops. To read the graph first look at the vertical axis which represents the degree of cognitive effectiveness the person might be performing at. The scale ranges from 0 to 100. Similar, but not exactly equivalent to a percent, the scale can be thought of as showing how effective the person is. For example, a score of 90 suggests that they might be at 90% effectiveness. In other words, the scale is showing a persons effectiveness or alertness on a scale of 0-100. It represents a person’s degree of effectiveness in completing simple tasks, detecting a change in environment, or solving problems within a given time frame. The horizontal axis shows the length of time awake or on duty. The solid bars at the base of the graphs show the person’s sleep/wake patterns and time of day. In figure 2, the red horizontal bar indicates the time period that the person was working. The blue horizontal bar indicates the time period that the person was sleeping. The grey bars indicate the period during which it was night-time or dark. The ‘optimal effectiveness cut-off level’ is indicated by a dotted line at approximately 75 per cent. A study conducted by the US DOT has suggested that effectiveness scores below 70 have been associated with a greater risk of having a human factors caused accident. Thus, when a person falls below 75 we begin to get concerned as they are approaching the “red zone” that occurs when a person falls below 70