Arrival type consists of six assigned categories for determining the quality of progression at a signalized intersection. This parameter approximates the quality of progression as follows:

1. Arrival Type 1 is characterized by a dense platoon of more than 80 percent of the lane group volume arriving at the start of the red phase.

2. Arrival Type 2 is characterized by a moderately dense platoon that arrives in the middle of the red phase or by a dispersed platoon of 40 to 80 percent of the lane group volume arriving throughout the red phase.

3. Arrival Type 3 consists of random arrivals in which the main platoon contains less than 40 percent of the lane group volume.

4. Arrival Type 4 consists of a moderately dense platoon that arrives in the middle of a green phase or of a dispersed platoon of 40 to 80 percent of the lane group volume arriving throughout the green phase.

5. Arrival Type 5 is characterized by a dense to moderately dense platoon of more than 80 percent of the lane group volume arriving at the start of the green phase.

6. Arrival Type 6 is reserved for exceptional progression quality on routes with near-ideal characteristics.