2 Del. Admin. Code § 5.1
The design of subdivision streets is required to be in accordance with applicable guidelines and standards, such as those listed in Section P.9.1 of this manual, which include but are not limited to: Manuals, Guidelines and Policies published by the American Association of State Highway and Transportation Officials (AASHTO); DelDOT's Road Design Manual (RDM); DelDOT's Bridge Design Manual; DelDOT's Design Guidance Memorandums (DGM); DE MUTCD; other Nationally Accepted Standards (NAS) and DelDOT's Development Coordination Manual. Where conflicts exist, DelDOT's Development Coordination Manual shall take precedence for subdivision streets.
In instances where the engineer determines that it is not in the best interest of the traveling public to comply with these standards, the engineer shall provide to DelDOT a written justification and rationale for their decision. DelDOT shall have the final authority on any process modifications, design exceptions, or design deviations.
The street layout of a subdivision has the following elements that must be considered by the developer and engineer:
The design criteria for subdivision streets shall be in accordance with Figure 5.1.2-a.
Figure 5.1.2-a Design Criteria for Subdivision Streets
* For upgrades and downgrades 3% or greater, refer to the AASHTO Green Book, A Policy on Geometric Design of Highways and Streets ( Table 3-2 of the 2011 Edition), or other NAS for adjusted values. Sufficient right-of-way dedicated to the State of Delaware shall be provided to maintain the required line- of-sight.
** Maximum street grades can be waived on an individual basis subject to DelDOT's engineering judgment with respect to the severity of the topography. Minimum street grades should be 0.5%.
Notes:
The intersection design of subdivision streets shall be in accordance with the following:
Figure 5.1.3-a Intersection Design Radii
Figure 5.1.3-b Maintaining Major Street Crown through Intersection
Figure 5.1.3-c Vertical Alignment Guidelines
G (%) = 1/RS x100
RS = 150 or reciprocal of relative longitudinal slope between the profile grade and outside edge of pavement of a two-lane street
The roadway crown of the major street is to be maintained.
An example as shown in Figure 5.1.3-d is a Type 1 subdivision street intersecting a Type II subdivision street having a 4% grade as shown below. The right outside edge of the Type 1 subdivision street must rotate from a -2% C.S. to a 4% C.S. or 0.72' and the left outside edge of the Type 1 subdivision street must rotate from a -2% C.S. to a -4% C.S. or 0.24'. Dividing 0.72' by G or 0.666% results in a transition length of 108' on the right outside edge of the Type 1 subdivision street. Dividing 0.24' by 0.666% results in a transition length of 36' on the left outside edge of the Type 1 subdivision street.
Figure 5.1.3-d Intersection Cross Slope Transition Example
Parking is not allowed on turnarounds and cul-de-sacs within subdivisions.
No driveways or parking bays shall be located in subdivisions within 40 feet from the edge of the radius return for the connecting street. This distance shall increase to 60 feet at the entrance to the subdivision.
Figure 5.1.4-a Subdivision Street Parking Provisions
In order to restrict parking in areas within a subdivision street that can accommodate overflow on-street parking, the DelDOT Traffic Section must receive a petition signed by 75% of the owners indicating their support for "Stopping, Standing, and Parking Restriction." DelDOT will determine whether to restrict on-street parking within subdivision streets considering the petition and engineering study performed by DelDOT.
The use of cul-de-sac and other closed end street design is to be limited to those situations where the developer's engineer meets the connectivity requirements of Section 3.5 or can justify that full street extensions are not possible based on topography, pre-existing development or environmental constraints.
Cul-de-sacs must be incorporated in the design of all permanent dead end streets except those eligible to be constructed within a reduced right-of-way. The minimum design criteria for cul-de-sacs are:
Figure 5.1.5.1-a Design Radii for Cul-de-Sacs
* Measured to the face of curb.
Developers planning streets with reduced right-of-way should select one of the turn-around designs shown in Figure 5.1.5.2-a in lieu of the standard cul-de-sac. Any alternative design must have prior approval of DelDOT.
Temporary dead end streets shall be constructed to the property line of the development in order to provide for future development of adjacent lands. A temporary turn around must be provided when the length of a temporary dead end street exceeds 200 feet. The additional right-of-way needed to accommodate a temporary turn around can be provided through a temporary easement which must be clearly labeled on the site plan. If the street segment is accepted for State maintenance, DelDOT will maintain the temporary dead end street in accordance with Chapter 6.
If the temporary dead end street shall ultimately provide connectivity to the adjacent property, the following shall apply:
For projects where the connection is internal, but will not be constructed until future phases, stub streets shall be constructed to extend to the end of the radii at the intersection with the future street. A sign stating "Future Internal Street and Connection to Future Development" and barricade, as shown in DelDOT's Standard Construction Details, shall be installed by the developer at the end of the stub street.
The sign shall be placed immediately after the placement of the base paving course. At DelDOT's discretion, the barricade requirement may be waived. Maintenance of the sign and barricade shall be the responsibility of the developer until DelDOT accepts the streets into the State maintenance system. Upon acceptance of the streets, the development's maintenance association assumes maintenance responsibility of sign. Refer to Figures 5.1.5.2-a and 5.1.5.2-b for stub street sign details.
Figure 5.1.5.2-a Design Alternatives in lieu of Cul-de-Sacs in Reduced Right-of-Way
(Not to Scale)
Figure 5.1.5.2-b Stub Street Sign Detail (Not to Scale)
The DelDOT Traffic Calming Design Manual (TCDM) provides detailed guidance regarding the appropriate use, design, signing and marking of traffic calming measures approved for use in Delaware. Even if the TCDM is not used for subdivision design, site design should be done in a manner so as to reduce the need for speed control devices after subdivision construction.
2 Del. Admin. Code § 5.1
15 DE Reg. 551 (10/01/11)
16 DE Reg. 1199 (5/1/2013)
18 DE Reg. 240 (9/1/2014)
18 DE Reg. 709 (3/1/2015)
19 DE Reg. 938 (4/1/2016) (Final)