For the purposes of analysing the vehicle flow on roads it is normal to monitor the frequency of vehicles in small time groups, over a period of months, and then average out the days in the months, to obtain an average flow for each day of the week. This will have the effect of removing, or at least reducing the effect of, unusual days, when the traffic flow was very different to normal. There is little use in trying to accommodate for these days as the change in traffic flow when something does upset the system is very hard to predict, if it is at all predictable.
I have covered two different types of queues that commonly occur on roads: