4.8.5 Vertical Alignment at Intersections

Adequate
intersection sight distance
 should be provided at intersecting roads.
At a minimum, stopping sight distance (measured from the edge of travel way of the intersecting facility) must be provided.
 The grades of intersecting roads should be as level as practical.
Approaching an intersection, drivers might misjudge the effect of steep grades on stopping or accelerating distances.
Approach grades steeper than 3 percent should be avoided within the stopping sight distance of the intersection. Where conditions make such designs impractical, grades should not exceed 6 percent.
At intersections where marked or unmarked crosswalks are present, the roadway profile grade within the crosswalks should be limited so that the crosswalk is accessible and usable by all individuals, including those with disabilities. The roadway profile grade across a crosswalk must not exceed:
  • 2 percent for an intersection with stop or yield control; or
    • Intersections with yield or stop control are those in which a vehicle must always slow or stop before proceeding through the intersection; for example, an intersection with a yield sign or stop sign.
  • 5 percent for all other intersections.
    • Intersections without yield or stop control are those in which a vehicle may proceed through the intersection without slowing or stopping; for example, an intersection with a traffic signal that has a green cycle phase, or an intersection without a yield sign or stop sign.
Accessibility accommodations should be considered when determining appropriate profile grades for all future crosswalk locations. See
Chapter 19
for additional guidance and when TDLR variances are required.
It is generally preferable to provide a smooth junction at intersecting streets. To accomplish this, the profile, cross slopes, and crowns of both roads are warped to create a common plane at the intersection. This technique is commonly referred to as
“table-topping.”
 Design features including but not limited to proper drainage and pedestrian use should be carefully considered when table-topping an intersection.
When table-topping of an intersection is not feasible and minor roadway traffic is expected to stop or travel slowly through the intersection, grades should generally favor the
major roadway
 (the roadway with the higher ADT) to provide a smooth profile. This is accomplished by warping the grades on the minor roadway to fit the cross-section of the major roadway. Similarly, for intersections contained within a horizontal curve with superelevation, an attempt should be made to match the superelevated section through the intersection.
Additional profiling of intersection features (e.g., curb, median islands, and curb ramps) may be required to ensure proper drainage and a smooth intersection surface.
Contours at appropriate intervals (e.g., 1-ft major and 0.25-ft minor contours) and key curb elevations should be shown in the plans for proper construction of such intersections.
 Low points near intersections must be designed to prevent water ponding within pedestrian access routes.
A minimum pavement edge profile grade of 0.30 percent should be maintained along corner radii of curbed intersections.
The combination of vertical and horizontal alignment should allow adequate sight distance at an intersection. A sharp horizontal curve following a crest vertical curve is undesirable, particularly on intersection approaches.