In this exercise, you will draw a spiral-curve-spiral system to connect tangent segments on the main roadway alignment. First, verify that you will use a clothoid spiral.

1. On the View menu, click Named Views to display the View dialog box. Under Name, select 3, click Set Current, and then click OK.

2. On the Lines/Curves menu, click Create Spirals Spiral Type to display the Spiral Type dialog box.

3. Verify that Clothoid is selected, and then click OK.

4. On the Lines/Curves menu, click Create Spirals Fit Tangent-Tangent to display the Fit Spirals - Tangent to Tangent dialog box.

5. From the Description list, select Spiral-Curve-Spiral, and then click OK.

6. Select the left tangent, and then select the right tangent.

7. Enter 850 m for the Radius, and then enter 300 for the Spiral A in value.

8. Press ENTER to accept the default, 300, for the Spiral A out value, and then press ENTER.

The tangents are connected with spirals and an 850 m radius curve.

Click here to see an illustration of the main alignment spiral-curve-spiral system.