Being a Patrol Officer Involves a Daily Onslaught of Choices

Being a patrol officer involves a daily onslaught of choices involving discretion. Imagine you are a patrol officer at an overtaxed department in a major city. It is the middle of February, and a nasty flu has taken out a quarter of your patrol officers. As a result, you've had to take on double shifts, which are technically not allowed by your department for more than three days in a row. It's been your fourth day and you are exhausted. It's a slow day and there's a place near a large cemetery where you can park and take a quick nap, which might help you clear your head and also keep you from getting sick. How do you determine whether to taking such a nap would be ethical?