In urban areas trucks and cars are sharing the roads, implying that when there is congestion road capacity used by one mode is at the expense of the other. Although cars and trucks have different trip distribution patterns and related to different economic and social activities, they both have peak periods of activity between 8AM and noon. Most trucks make their deliveries when businesses are open and able to receive shipments, particularly in the morning.
Morning deliveries are often preferred since stores are less busy with more employees available for unloading, unpacking, and stacking. Goods are thus available for the more active afternoon and evening retail activities. This pattern compounds congestion problems during the morning and afternoon since they correspond to periods of high activity for both car and truck movements.