This calculator helps engineers analyze traffic flow using the Greenshields model. It's designed for civil and transportation engineers needing accurate traffic flow parameters.
Calculator
Results
Data Source and Methodology
All calculations are based on the formulas provided by authoritative sources in traffic engineering. Consult the Greenshields Model Reference for more information.
The Formula Explained
The Greenshields model calculates traffic flow using the formula:
Q = V_f × D × (1 - D / D_j)
Glossary of Terms
- Traffic Density (D): The number of vehicles per kilometer.
- Free Flow Speed (Vf): The speed of vehicles when no other vehicles are present.
- Traffic Flow (Q): The rate at which vehicles pass a point on the road.
How It Works: A Step-by-Step Example
Assume a traffic density of 20 vehicles/km and a free flow speed of 100 km/h. The traffic flow is calculated as follows:
- Calculate the adjustment factor:
(1 - 20 / 100). - Multiply by the free flow speed:
100 × 20 × 0.8 = 1600 vehicles/hr.
Frequently Asked Questions (FAQ)
What is the Greenshields model?
The Greenshields model is a linear model of traffic flow that assumes a linear relationship between speed and density.
How do I use this calculator?
Enter the traffic density and free flow speed to calculate the traffic flow using the Greenshields model.
What is traffic density?
Traffic density is the number of vehicles per unit length of road, usually expressed as vehicles per kilometer.
What is free flow speed?
Free flow speed is the speed of a vehicle when there are no other vehicles to slow it down.
Can the Greenshields model be used for all types of roads?
While the Greenshields model is useful for many road types, it may not apply to roads with complex conditions or varying speed limits.