Curb Radius Calculator

Formula

To calculate the Curb Radius (CR):

$$CR = \frac{VT}{\tan(EA) + \tan(XA)}$$

Where:

CR is the curb radius (feet)
VT is the vehicle trajectory (feet)
EA is the entry angle (degrees)
XA is the exit angle (degrees)

What is a Curb Radius?

A curb radius is the curved edge of a roadway at an intersection or entrance to a roadway. It is designed to accommodate the turning path of vehicles, particularly larger ones like buses and trucks. A properly designed curb radius allows vehicles to make turns without encroaching on other lanes and ensures pedestrian safety by controlling the speed of turning vehicles.

Example Calculation 1

Let's assume the following values:

Vehicle Trajectory (VT) = 50 feet
Entry Angle (EA) = 30 degrees
Exit Angle (XA) = 45 degrees

Using the formula:

$$CR = \frac{50}{\tan(30) + \tan(45)} = \frac{50}{0.577 + 1} = \frac{50}{1.577} ≈ 31.71 \text{ feet}$$

The Curb Radius is approximately 31.71 feet.

Example Calculation 2

Let's assume the following values:

Vehicle Trajectory (VT) = 60 feet
Entry Angle (EA) = 35 degrees
Exit Angle (XA) = 40 degrees

Using the formula:

$$CR = \frac{60}{\tan(35) + \tan(40)} = \frac{60}{0.700 + 0.839} = \frac{60}{1.539} ≈ 38.99 \text{ feet}$$

The Curb Radius is approximately 38.99 feet.