This Chapter discusses SHA's standards for street connections that provide access to public or private subdivision roads or provide any other public road intersection with a State highway. These standards are applicable to all proposed connections and any existing connections subject to State regulation.

12.1 Horizontal Layout

12.1.1 Width of Street Connection.

The State standard width for a two-way street connection is 30' minimum. This provides for two 15' curb lanes when the connection is channelized. When an open section is acceptable for the connection, the minimum width is also 30', providing for two 11' lanes and 4' shoulders. Refer to the typical details in Appendix B.

12.1.2 Angle of Street Connection.

The angle of intersection, measured as the angle between the centerline of the State highway and the centerline of the street, shall be not less than 70 degrees or greater than ll0 degrees. Every attempt shall be made to provide a connection at 90 degrees.

12.1.3 Intersection Radius.

  1. At the intersection of a State highway with a minor road (county, municipal, etc.) the minimum radius shall be a 30 foot or equivalent 3-centered compound curve.
  2. At the intersection of a State highway with a State highway or other major arterial highway, the minimum radius shall be a 50 foot or equivalent 3-centered compound curve. The appropriate radius shall be determined by analyzing the turning movement for the design vehicle.
  3. At intersections with channelization providing for free right turns, the above mentioned dimensions will be increased as directed by SHA in accordance with accepted engineering practices. The proper radius for this situation will allow the design vehicle (WB-62, WB-67, SU, etc.) to comfortably negotiate through the right turn into the receiving lane without encroaching into the adjacent through lane(s).
  4. At intersections where a significant volume of vehicles that require a large turning radius are expected (e.g. tractor trailers, single unit vehicles, industrial areas, along primary routes), the design vehicle for intersection design purposes shall be identified and reviewed with the Assistant District Engineer – Traffic. Near Interstate routes and primary highways, the appropriate design vehicle for effective intersection operations is a WB-67.
  5. Where multiple left turn lanes are being considered, the intersection design does not necessarily need to accommodate side-by-side design vehicle passage through the turn. However, a design vehicle and a passenger car should be able to negotiate the turn simultaneously without interfering with opposing left turns under the same phase.

12.1.4 Traffic Control Islands.

Traffic control islands shall be provided where appropriate for the anticipated turning movements and constructed in accordance with the standards given in 15.9. A right-in/right-out design, similar to that used for commercial entrances, may be required for street connections along divided highways. Refer to 11.1.4.B for guidance on appropriate application of this design.

12.1.5 Monumental Entrances.

Monumental entrances are generally not appropriate for public street connections to the State highway. Where the street is to have a divided or channelized cross section on-site, this section shall be introduced outside of the State's right of way. Provisions for u-turns shall be made on-site beyond the intersection area, by way of channelized turn bays or connection with other site roads.

12.2 Vertical Layout

12.2.1 Maximum Landing Grade for Public Streets.

The profile grades of intersecting streets should be as flat as possible on those sections that are to be used for storage space for stopped vehicles. Grades in excess of 3 percent may not be allowed on the landing grade (first 50 feet) of intersecting public streets, unless otherwise approved by the administration. Grades beyond the landing grade shall be in accordance with currently accepted engineering practices, but may not exceed 6 percent. Design using vertical curves is recommended.

12.2.2 Grade Breaks.

The maximum allowable grade break between the preference road cross slope and the profile grade of the non-preference public road is normally 5%. This allows for a landing grade of up to 3% on the non-preference road when the cross slope of the preference road is 2%. In the case of superelevated highway cross sections, a grade break of up to 7% may be allowed. This accommodates a landing grade of up to 3% on the non-preference road when the preference road cross slope is superelevated at up to 4%.

12.2.3 Grading and Drainage Provisions.

The profile grade lines and cross sections on the non-preference intersecting streets shall be designed to provide a smooth junction and proper drainage. Normally, the grade line of the major highway should be carried through the intersection, and that of the intersecting street should be adjusted to it.

12.2.4 Vertical Layout for Private Streets.

The vertical layout for private street connections shall conform to the criteria for Commercial Entrances given in 11.3.

12.2.5 Entrance Profile.

A profile of all street connections shall be supplied for EAPD review. The profile shall be submitted on a scale drawing showing existing and proposed grade lines at the centerline of the highway and along the radius returns (fillet profiles) of the intersection. All grades and control points shall be clearly identified. The existing and proposed profile grades along the centerline of the entrance shall be shown extending from the preference road centerline into the site for a distance sufficient to demonstrate compliance with the above standards. All grades, elevations, offsets, flow lines, grade breaks, and controls shall be clearly labeled and drawn to scale.