• Civil 3D

Draw an alignment for a road and add curves

Draw an alignment for a road in Civil 3D using the Tangent-Tangent (no curves) tool, and then add curves individually.


00:03

Civil 3D alignments are key components in civil engineering,

00:07

guiding the design of roads, railways, and utilities.

00:12

They define the center line and geometry for transportation routes, utility layouts, and land development projects.

00:21

Alignments are essential for creating accurate 3D corridor models, performing earthwork calculations,

00:27

and designing intersections, roundabouts, and bridges.

00:32

To create an alignment in Civil 3D, begin with a drawing open and a grading object already placed.

00:40

On the Home tab, Create Design panel, expand the Alignment drop-down, and select Alignment Creation Tools.

00:48

In the Create Alignment – Layout dialog, Name field, enter an alignment name.

00:56

Here, the alignment is named after the road it will represent.

00:60

Next, expand the Type drop-down to specify the type of alignment,

01:05

which in this case, is Centerline.

01:08

From the General tab, expand the Site drop-down and specify a site.

01:14

Ensure that this is the same site as your grading object,

01:18

so that the alignment and grading object will interact with each other.

01:22

Expand the Alignment style drop-down and specify a style,

01:27

which controls the visual appearance of alignment components and labels.

01:32

Finally, in the Alignment label set drop-down,

01:35

specify a label style to apply labels along the alignment at specific points,

01:40

such as the major and minor stations or geometry points.

01:45

For this example, select all labels.

01:48

Click OK.

01:50

The Alignment Layout Tools toolbar displays,

01:53

with both freehand and constraint-based alignment creation and editing tools.

01:59

Expand the Tangent drop-down to add tangents with or without curves.

02:04

If you are adding curves, you can also select Curve and Spiral Settings

02:09

to enter the curve settings and to specify the spiral defaults.

02:14

However, in this instance, since none of the curves are consistent, they will need to be added individually.

02:21

The road also needs to stay within a pre-designated alignment right of way,

02:26

so Tangent-Tangent (No curves) is selected.

02:30

You are prompted to specify a starting point.

02:34

In this example, it is a specific point number, because it is the end point of a centerline that already exists.

02:41

From the Transparent Commands toolbar, select Point number.

02:45

Enter the point number to connect to, then press ESC to exit the transparent command.

02:52

The bearing and distance for the right of way are known,

02:55

and you want to stay within that right of way.

02:58

From the Transparent Commands toolbar, select Bearing Distance.

03:03

When prompted to select a quadrant, here, enter 2 for Southeast.

03:09

Next, type in the bearing, starting with degrees, followed by a decimal point,

03:14

and then the minutes and seconds.

03:17

Finally, enter the distance along that bearing.

03:23

Continue typing in bearing and distance values to complete the alignment,

03:29

then press ESC twice to exit the command.

03:34

Since most roads do not have sharp corners like these,

03:40

the next step is to add some curves.

03:43

From the Alignment Tools toolbar, expand the Curve drop-down.

03:48

Floating or Free Curves are recommended for smooth transitions,

03:52

because these curves stay tangent, even if you change the point of intersection.

03:56

In this case, all curves will be applied as Free Curve Fillet (Between two entities, radius),

04:03

since the radius is known.

04:05

To create a curve, select the beginning and ending entities by picking a point on each side of the intersection point.

04:12

Then, choose whether the curve is greater than or less than 180°.

04:18

Here, select Lessthan180.

04:22

Next, set the radius to 150.

04:27

When you press ENTER, the curve is applied, and notice that the command stays active,

04:33

so you can continue adding curves.

04:35

Here, one more curve is added using the radius.

04:39

However, suppose that for the next selected entity, the tangent length is known.

04:45

From the command line, click Tangent Length, and then enter a tangent length of 36.

04:53

Proceed to the next entity, continuing around the alignment.

04:58

When you are done adding curves, press ENTER.

05:01

The system will automatically label them according to the style you selected previously.

05:09

To make any modifications, select the alignment.

05:13

Since free curves were applied,

05:16

the curves will stay tangent, even if you change the alignment location.

Video transcript

00:03

Civil 3D alignments are key components in civil engineering,

00:07

guiding the design of roads, railways, and utilities.

00:12

They define the center line and geometry for transportation routes, utility layouts, and land development projects.

00:21

Alignments are essential for creating accurate 3D corridor models, performing earthwork calculations,

00:27

and designing intersections, roundabouts, and bridges.

00:32

To create an alignment in Civil 3D, begin with a drawing open and a grading object already placed.

00:40

On the Home tab, Create Design panel, expand the Alignment drop-down, and select Alignment Creation Tools.

00:48

In the Create Alignment – Layout dialog, Name field, enter an alignment name.

00:56

Here, the alignment is named after the road it will represent.

00:60

Next, expand the Type drop-down to specify the type of alignment,

01:05

which in this case, is Centerline.

01:08

From the General tab, expand the Site drop-down and specify a site.

01:14

Ensure that this is the same site as your grading object,

01:18

so that the alignment and grading object will interact with each other.

01:22

Expand the Alignment style drop-down and specify a style,

01:27

which controls the visual appearance of alignment components and labels.

01:32

Finally, in the Alignment label set drop-down,

01:35

specify a label style to apply labels along the alignment at specific points,

01:40

such as the major and minor stations or geometry points.

01:45

For this example, select all labels.

01:48

Click OK.

01:50

The Alignment Layout Tools toolbar displays,

01:53

with both freehand and constraint-based alignment creation and editing tools.

01:59

Expand the Tangent drop-down to add tangents with or without curves.

02:04

If you are adding curves, you can also select Curve and Spiral Settings

02:09

to enter the curve settings and to specify the spiral defaults.

02:14

However, in this instance, since none of the curves are consistent, they will need to be added individually.

02:21

The road also needs to stay within a pre-designated alignment right of way,

02:26

so Tangent-Tangent (No curves) is selected.

02:30

You are prompted to specify a starting point.

02:34

In this example, it is a specific point number, because it is the end point of a centerline that already exists.

02:41

From the Transparent Commands toolbar, select Point number.

02:45

Enter the point number to connect to, then press ESC to exit the transparent command.

02:52

The bearing and distance for the right of way are known,

02:55

and you want to stay within that right of way.

02:58

From the Transparent Commands toolbar, select Bearing Distance.

03:03

When prompted to select a quadrant, here, enter 2 for Southeast.

03:09

Next, type in the bearing, starting with degrees, followed by a decimal point,

03:14

and then the minutes and seconds.

03:17

Finally, enter the distance along that bearing.

03:23

Continue typing in bearing and distance values to complete the alignment,

03:29

then press ESC twice to exit the command.

03:34

Since most roads do not have sharp corners like these,

03:40

the next step is to add some curves.

03:43

From the Alignment Tools toolbar, expand the Curve drop-down.

03:48

Floating or Free Curves are recommended for smooth transitions,

03:52

because these curves stay tangent, even if you change the point of intersection.

03:56

In this case, all curves will be applied as Free Curve Fillet (Between two entities, radius),

04:03

since the radius is known.

04:05

To create a curve, select the beginning and ending entities by picking a point on each side of the intersection point.

04:12

Then, choose whether the curve is greater than or less than 180°.

04:18

Here, select Lessthan180.

04:22

Next, set the radius to 150.

04:27

When you press ENTER, the curve is applied, and notice that the command stays active,

04:33

so you can continue adding curves.

04:35

Here, one more curve is added using the radius.

04:39

However, suppose that for the next selected entity, the tangent length is known.

04:45

From the command line, click Tangent Length, and then enter a tangent length of 36.

04:53

Proceed to the next entity, continuing around the alignment.

04:58

When you are done adding curves, press ENTER.

05:01

The system will automatically label them according to the style you selected previously.

05:09

To make any modifications, select the alignment.

05:13

Since free curves were applied,

05:16

the curves will stay tangent, even if you change the alignment location.

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