Speed Calculator

Step 1: Enter the Number of Vehicles

Begin by entering the total number of vehicles that pass a single point during your observation period. This can be a sensor, a stoplight, or even a manual count taken while monitoring a road. This count is used to calculate traffic flow.

Example:

If 90 vehicles pass a traffic light in your observation, input 90.

Step 2: Enter the Time Duration (in Seconds)

Next, enter the time interval over which those vehicles were counted, expressed in seconds. This value is essential for scaling traffic activity to an hourly rate, which is standard in transportation analysis.

Example:

If the count was taken over a 30-second interval, input 30.

Step 3: Input the Road Segment Length (in Kilometers)

Then, provide the length of the road section being analyzed. This tells the calculator how much road space the vehicles are occupying, which is needed to compute density (vehicles per kilometer).

Example:

If your observed road segment is 1.5 km long, enter 1.5.

Step 4 (Optional): Enter the Average Speed (in km/h)

If you know the average travel speed of vehicles on the road during your observation, you can enter it manually. If left blank, the calculator will estimate speed using the formula:

 Speed = Flow ÷ Density

This flexibility is helpful for both real-world studies and modeling scenarios.

What the Calculator Does Behind the Scenes

Once your inputs are submitted, the calculator instantly performs the following:

Traffic Flow (vehicles/hour)

Indicates how many vehicles pass a specific point in one hour, assuming consistent conditions.

 Formula:

Flow = (Number of Vehicles/Time (seconds)) × 3600

Example:

90 vehicles in 30 seconds → (90 ÷ 30) × 3600 = 10,800 vehicles/hour

Traffic Density (vehicles/km)
Tells you how crowded the road is — that is, how many vehicles occupy every kilometer of road space.

Formula:

Density = Vehicles/Road Length (km)​

Example:

90 vehicles over 1.5 km → 90 ÷ 1.5 = 60 vehicles/km

Headway (meters)

Headway reflects the average distance between two vehicles traveling in the same lane. It’s a safety metric and helps with signal timing and lane design.

Formula:

Headway = ( 3600 Flow) × 1000
​

Example:

Flow of 10,800 → (3600 ÷ 10,800) × 1000 = 333.33 meters

Travel Speed (km/h)

If you didn’t provide speed, the calculator estimates it from flow and density.

Formula:

Speed = Flow/Density​

Example:

Flow = 10,800, Density = 60 → 10,800 ÷ 60 = 180 km/h

(If this seems high, it likely means low congestion and high flow rates.)