What is traffic congestion?

Traffic congestion is a traffic phenomenon characterized by slower vehicle speeds, longer trip times, and increased queuing of vehicles. It influences the movement patterns in cities and how roads are used.

What causes traffic congestion?

Traffic congestion occurs when the number of vehicles is larger than the capacity of a road or intersection. As a result, vehicles pile up, velocity decreases, and trip time increases. The point at which road or intersection capacity equals traffic demand is referred to as saturation.

Traffic demand often grows over time; thus, traffic congestion can occur simply because the road or intersection capacity has not been designed for the actual traffic demand, especially during peak hours. Negative conditions like rain, snow, construction works, or accidents can reduce the capacity of roads and intersections.

Common types of traffic congestion origins include:

• Traffic-influencing events: Weather conditions like rain or snow, construction works, or accidents can reduce the capacity of roads and intersections.
• Gridlock: This means that all roads leading to a major intersection become blocked, making it impossible for any cars to pass through the intersection.
• Bottleneck: This happens when a certain section of road becomes too narrow for all cars, causing some to slow down or even stop completely.
• Shockwave: This occurs when one car suddenly slams on its brakes, causing several other cars behind it to also slow down or stop.
• Congestion caused by special events: Certain events, such as football games or concerts, can cause increased traffic due to the influx of large numbers of people coming into the area.

What is the difference between traffic congestion and traffic jam?

Traffic jam describes the situation when traffic is completely halted. Thus, a traffic jam is worse than traffic congestion.

How can traffic congestion be classified?

Level of Service (LOS) is a metric that classifies congestion depending on its severity.

Effects of traffic congestion

Traffic congestion has significantly negative effects. It causes:

• Increased carbon emissions as a result of idling in traffic
• Increased vehicle consumption, which results in higher fuel costs.
• Increased trip duration reduces the time spent productively.
• Trip delays can result in missed appointments.
• Increased chances of road accidents.
• Wear and tear on vehicles as a result of idling in traffic and frequent acceleration and braking.
• Emergency vehicles have longer trip times to reach accidents and bring wounded people to the hospital.

How can traffic congestion be mitigated?

Traffic can either be reduced by increasing road system capacity or by reducing demand.

Reducing traffic demand

For most of the measurements for reducing traffic demand, political initiatives are needed. Programs such as the European Green Deal and the US Bipartisan Infrastructure Law aim to reduce the emission of CO₂ in the transport sector.

Reducing traffic demand can be done by:

• Promoting modal shift to public transport
• Promoting modal shift to cycling
• Promoting the concept of 15-minute cities
• Car sharing
• Autonomous driving

Increasing road capacity

Increasing the road system capacity can be done by planning, designing, and building roads and intersections with higher capacity, but also by using existing infrastructure more intelligently.

Intelligent Transport Systems (ITS) are systems to provide smart means of transportation. ITS continuously monitors traffic conditions such as demand, weather, and accidents. The obtained information is then used to actively manage traffic and reduce congestion and accidents.

Some measures to increase capacity or mitigate the negative effects of traffic congestion with ITS include:

• Hard shoulder running
• Variable message signs
• Emergency vehicle preemption
• Parking management and guidance systems
• V2X communication
• Coordinated Traffic Adaptive Signals
• Transit Signal Priority
• Automatic accident detection

Solving traffic congestion with real-time data

To effectively solve traffic congestion problems, cities and road authorities need real-time data to make accurate decisions based on reality. Static counts and outdated historical trends are no longer enough to manage dynamic urban mobility. The video below shows how intelligent video analytics can be used together with regular security cameras to obtain real-time information about traffic flow and congestion.

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Isarsoft Perception transforms traffic camera infrastructure into intelligent, real-time sensors that continuously monitor traffic density, detect bottlenecks, and analyze flow patterns as they happen. By equipping traffic management centers with actionable insights, Isarsoft enables authorities to adapt dynamically, optimize signal controls, and keep roads moving.

Ready to transform your road network? Explore our traffic management solutions to see how Isarsoft can help your city reduce congestion.

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Further Reference:

• FHWA: Traffic Congestion and Reliability: Trends and Advanced Strategies for Congestion Mitigation