Curb ramps type 1A

crdr-ele-crb-rmp-1a-01.mp4 6:50

The key to correctly modeling the type 1A curb ramp is determining the correct critical curb cut locations. Since the sidewalk it placed directly at the back of curb, the ramp slope is determined by the curb cut taper slopes. The slope along the curb return alignment must be a consideration when creating the curb cut. As the slope increases/decreases, the curb cut transitions length must be adjusted to achieve the required ramp slope.

Example: Required maximum slope for Type 1A curb ramp sides = 8.3%

Curb Height = 0.5 ft

For a flat curb return profile, ramp side slope lengths = 0.5/.083 = 6 ft

Actual curb return profile = 1%

Therefore, high side ramp side slope min length = 0.5/(.083-.01) = 6.8 ft

The low side ramp side slope remains at the minimum 6 ft length per SDD 8D5-15a

The curb cuts can be made using the same superelevation method described in the previous curb ramp training.

Sidewalk is added to the back of curb on curb return is assembly. The ultimate surface created by adding the sidewalk to the assembly is not the final curb ramp surface. This portion of the surface will be used as a setup surface for the curb ramp.

Create an alignment representing the back of curb. Then, create a surface profile on the using the back of curb alignment and Crdr-Ultimate surface. Use the surface profile to verify the slopes meet standards. Adjust the curb transition lengths as needed. We recommend that you do not set the curb transition lengths so the slopes are at the maximum (8.3%). Provides some level of tolerance so there is flexibility for design refinement in the intersection.

crdr-ele-crb-rmp-1a-02.mp4 4:04

The curb ramp setup corridor for the Type 1A ramp is the same concept covered in the previous curb ramp modeling training.

1. Create an auxiliary alignment and surface profile for the curb ramp setup corridor baseline.
2. The same curb ramp setup assembly can be used. However, since the curb ramp perpendicular to the curb return, the triangular lower landing does not exist. Therefore, the additional LinkWidthAndSlope subassembly representing that area can be removed from the assembly.

Create data shortcuts for the curb return back of curb alignments, curb return outside sidewalk alignments, CrdrUltimate surface, and Crdr-Setup-CurbRamps surface.

crdr-ele-crb-rmp-1a-03.mp4 5:08

Open the curb ramp corridor.dwg file. Data reference the curb return back of curb return alignment, Crdr-Ultimate surface, Crdr-Setup-CurbRamps surface.

1. Create a new alignment representing the outside sidewalk. This can be an offset alignment to the back of curb or it can be a centerline alignment. It should not be a miscellaneous alignment because superelevation will be assigned in a later step.
2. Create a new alignment representing the curb ramp. View the Crdr-Setup-CurbRamps surface with triangles turned on. This will allow for easy placement of the alignment Pis.

crdr-ele-crb-rmp-1a-04.mp4 7:02

1. Turn the Crdr-Setup-CurbRamps surface triangles off. Turn the Crdr-Ultimate surface triangles on. Orbit around the surface to find the tops of the curb transistions. Mark them with polylines. Return to Top view
2. Create the two alignments representing the top of the ramp sides, where the curb ramp matches into the adjacent sidewalk. Use the polylines created in the previous step to locate the intersection of the Crdr-Ultimate triangle edge and the back of curb alignment.

3. Then use the station offset transparent command to locate a second PI so the alignment is perfectly parallel to the ramp alignment.
4. The PI can now be moved using the extend OSNAP and snapped to the outside sidewalk alignment.
5. Since intersection objects cannot be used at the ends of an alignment, the alignment must be extended down the back of sidewalk alignment a small distance. The resulting alignments should look like this:

crdr-ele-crb-rmp-1a-05.mp4 5:07

1. Create a surface profile for the ramp alignment. The surface profile is created on the Crdr-SetupCurbRamps surface.
2. Create a surface profile for the match alignments. These surface profiles are created on the CrdrUltimate surface.
3. Create a surface profile for the back of curb alignment. This surface profile is created on the CrdrUltimate surface.
4. Create a surface profile for the outside sidewalk alignment. This surface profile is created on the Crdr-Ultimate surface.
5. Create a profile view for the outside sidewalk alignment. Create an arbitrary profile that extends beyond the limits of the alignment. These elevations will be determined using intersection objects.
6. Create intersection objects in the following locations along the outside sidewalk alignment.
   • Intersections with the two match alignments
   • Intersections with the two ends of the ramp alignment.
7. Delete the end tangents from the profile.

crdr-ele-crb-rmp-1a-06.mp4 5:06

1. Add the back of curb, outside sidewalk, ramp, and match alignments as base lines in the curb ramp corridor.
2. Using the CurbRamp-Basic assembly, add a region for the back of curb baseline. For now, the region extents should be to the ends of the match alignments or beyond. These extents will be refined later.

3. Add three regions to the ramp alignment baseline. Using the CurbRamp-Basic assembly, the first region should start at the back of curb and end at the outside sidewalk. Using a null assembly, the second region should follow the portion that is coincident with the outside sidewalk alignment. Using the CurbRamp-Basic assembly, the third region should start at the outside sidewalk and end at the back of curb.

4. Using the CurbRamp-Basic assembly, add a region to each match alignment baseline. The regions should extend from the back of curb to the outside sidewalk only.

crdr-ele-crb-rmp-1a-07.mp4 6:58

1. Make a copy of the CurbRamp-Basic assembly. Rename the copy “CurbRamp-PedCurb”. Change the LinkWidthAndSlope subassembly to a slope of 5000% and set it to use the Right Inside Lane Superelevation. Change the point code to Top_Curb.
2. Add a second LinkWidthAndSlope at the end of the first LinkWidthAndSlope. Set its parameters to slope = 0%, No Superelevation, Point Code = Back_Curb, Width = 0.5 ft.
3. Add the appropriate daylight subassembly to the CurbRamp-WithPedCurb assembly.
4. Using the CurbRamp-WithPedCurb assembly, add a region to the outside sidewalk base line. The region should extend from one match alignment to the other. Set the frequency for this region to 1 ft.

5. Set the outside sidewalk alignment superelevation for controlling the pedestrian curb.
   • Begin alignment: Right Inside Lane = 0%
   • At Match Alignment 1: Right Inside Lane = 0%
   • At Ramp intersection 1: Right Inside Lane = 5000%
   • At Ramp Intersection 2: Right Inside Lane = 5000%
   • At Match Alignment 2: Right Inside Lane = 0%
   • At end of Alignment: Right Inside Lane = 0%

crdr-ele-crb-rmp-1a-08.mp4 5:31

1. Make another copy of the CurbRamp-Basic assembly. Rename it to “CurbTransition”. Change the MarkPoint subassembly point code to Top_Curb. Add the appropriate daylight subassembly to the end of the LinkWidthAndSlope subassembly. Change the LinkWidthAndSlope subassembly point code to Back_Curb and the width to 0.001’.
2. Add another base line for the outside sidewalk alignment. This time, use the Crdr-Ultimate surface profile.
3. Add three regions to the new outside sidewalk alignment baseline. Using the CurbTransition assembly, the first region should start at few feet before the intersection with the match alignment. Using a null assembly, the second region is the area between the match alignments. Using the CurbTransition assembly, the third region should start at the intersection with the other match alignment and extend a few feet past.

4. Draw two polylines from the end of the Back of Curb feature lines to the ends of the curb transition regions. Target the 2 polylines with the CurbTransition assembly.

5. Make sure the back of curb region limits match the ends of the curb transition regions.

crdr-ele-crb-rmp-1a-09.mp4 3:12

1. Add all the necessary feature lines to define the surface.

2. Create a hide boundary for the concave area outside the daylight feature line.