Chapter 3 – Street Connection Standards

3.1   Horizontal Layout

• 3.1.1   Width of Street Connection – Refer to the typical details for street connections in Standard Entrance and Street Connection Details for guidance on common two-way street connection widths and layouts.

• 3.1.2   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 110 degrees. Every attempt shall be made to provide a connection at 90 degrees.

• 3.1.3   Intersection Radius

  • 3.1.3.A.   At the intersection of a state highway with a minor road (county, municipal, etc.) the minimum radius shall be a 30’ or equivalent 3-centered compound curve.
  • 3.1.3.B.   At the intersection of a state highway with another state highway or other major arterial highway, the minimum radius shall be a 50’ or equivalent 3-centered compound curve. The appropriate radius shall be determined by analyzing the turning movement for the design vehicle.
  • 3.1.3.C.   At intersections with channelization providing for free right turns, the dimensions noted above will be increased as directed by MDOT 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).
  • 3.1.3.D.   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.
  • 3.1.3.E.   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.

• 3.1.4   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 5.9 Curb-and-Gutter, Medians, and Traffic Control Islands. A right-in/right-out design, similar to that used for commercial entrances, may be required for street connections along divided highways. Refer to 2.1.4.B for guidance on appropriate application of this design.

3.2   Vertical Layout

• 3.2.1   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.

• 3.2.2   Grade Break – 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%.

• 3.2.3   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.

• 3.2.4   Vertical Layout for Private Streets – The vertical layout for private street connections shall conform to the criteria for commercial entrances given in 2.3 Vertical Layout.

• 3.2.5   Entrance Profile – A profile of all street connections shall be supplied for MDOT SHA 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.