CORSIM, VISSIM, and TRANSIMS: Tools for Traffic Engineers or Traffic Models?

Understanding the distinction between tools and models in traffic engineering can significantly enhance the effectiveness of traffic analysis and planning. While many may differentiate between tools and models based on their perceived functions, it's crucial to recognize that tools like CORSIM, VISSIM, and TRANSIMS straddle this line, providing immense value both to model traffic scenarios and to solve practical engineering problems.

Models as the Foundation of Traffic Analysis

At their core, CORSIM, VISSIM, and TRANSIMS are sophisticated traffic models designed to simulate various traffic scenarios accurately. These models incorporate numerical algorithms and are based on mathematical representations of real-world traffic systems. By feeding this system with empirical data from traffic counts, geometry, signals, and signs, engineers can create detailed simulations that reflect real traffic conditions.

The primary purpose of these models is to enable traffic engineers to validate their simulations against actual field measurements. Parameters such as queue length, flows, and speeds can be compared to real-world data to ensure the model's accuracy. This validation process is known as calibration and is a critical step in ensuring that the model accurately reflects the current traffic situation.

Parameters and Calibration for Model Refinement

The sophistication of CORSIM, VISSIM, and TRANSIMS lies in the numerous parameters they allow engineers to adjust. Some key parameters include:

Gap Acceptance in Stop Signs: The distance or time gap that allows a vehicle to enter an intersection safely. Start Time for the First Car to Cross the Intersection: The time when the first vehicle can start its travel through the intersection. Subsequent Traffic Flow at Traffic Signals: How subsequent vehicles in a queue are allowed to proceed. Distribution of Free Flow Speeds of Vehicles: The range of speeds vehicles maintain when no congestion is present. Compliance with Assumed Average Speed in 'Green Waves': Coordination of traffic lights to allow continuous flow of traffic at a specific speed.

These parameters, when adjusted appropriately, can significantly enhance the model's accuracy, ensuring that it closely mirrors real-world traffic conditions.

From Simulation to Prediction and Optimization

Once a model has been accurately calibrated, traffic engineers use it for predictive modeling. This involves changing various parameters and scenarios to forecast future traffic conditions. For instance, modifications to infrastructure, such as changing the geometry of intersections or adjusting traffic light timing, can be simulated to find the most optimal traffic design.

Predicting Future Traffic Conditions: By inputting projected traffic volume data, engineers can predict potential congestion, low speeds, and delays. This is not only useful for planning future traffic infrastructure but also for evaluating the impact of proposed solutions.

Evaluating Engineering Solutions: These traffic models are invaluable for demonstrating the potential benefits of proposed traffic engineering solutions. For example, they can show the reduction in pollution, gasoline usage, and electricity consumption if new traffic designs are implemented, helping to justify such solutions from a cost-benefit perspective.

In conclusion, tools like CORSIM, VISSIM, and TRANSIMS are not just models—they are powerful tools that bridge the gap between theoretical traffic analysis and practical engineering solutions. They enable traffic engineers to create, validate, and refine models that predict future traffic scenarios, ultimately leading to more effective traffic management and planning.

strongKeywords:/strong CORSIM, VISSIM, TRANSIMS