Final answer:
The hardest thing to control within the highway traffic system is traffic congestion, which can cause major delays, reduce the efficiency of the transportation system, and increase pollution levels. Various strategies can be implemented to address traffic congestion, such as the construction of additional roads or the improvement of public transportation systems.
Step-by-step explanation:
The hardest thing to control within the highway traffic system is traffic congestion. Traffic congestion can cause major delays, reduce the efficiency of the transportation system, and increase pollution levels. It occurs when there is an excessive number of vehicles on the road, leading to slow speeds and congestion.
One example of traffic congestion is shown in the image of Delhi, India. It demonstrates how slow speeds and idling vehicles can create a significant problem in urban centers.
To address traffic congestion, various strategies can be implemented, such as the construction of additional roads or the improvement of public transportation systems. These measures aim to alleviate congestion and provide efficient mobility for commuters.