The delay caused by an incident depends on many variables. This paper introduces an analytical expression for the delay, describing the location and length of the queue by shockwave theory. As long as the congestion remains on the same link, delay is proportional to the square of the duration, even in case the outflow is reduced by a junction downstream. This gives an elegant expression for the expected delay. Once the queue grows to other links (spillback or blocking back), the influence of duration becomes even larger. Therefore, it is useful to avoid spillback by network design or reduce incident times as much as possible.