Design Elements — Planted Cul-de-sacs and Bump-outs
When a subdivision design includes cul-de-sac turn arounds, attractively landscaped islands should be required at the center of the cul-de-sac to reduce impervious surface and provide a more attractive view. Similarly, when on-street parking is provided (or even when it is not), planted intersection bump-outs can be encouraged or required. Bump-outs can function as green stormwater infrastructure, planting areas, and streetscaping element that reduce the pedestrian crossing distance at intersections.
A planted cul-de-sac island in the Greens at Penn Oaks in 2000 (left) and 2022 (right) illustrating the positive impacts of mature vegetation.
Ordinance Considerations
The landscaping standards for cul-de-sacs and intersection bump-outs can be included in the street standard section of the subdivision and land development ordinance and should apply to all types of subdivisions.
Sample Ordinance Language for Cul-de-sac Turnarounds
Boulevards may be provided as the primary entrance into a proposed development and shall meet the following design standards:
- Cul-de-sac turnarounds shall be designed with a landscaped center island.
- The island shall be landscaped with a permanent groundcover to be shown on the landscaping plan submitted with the preliminary plan.
- The center island shall have mountable curbs unless otherwise approved to accommodate alternative stormwater best management practices.
- Maintenance responsibility of such islands shall be determined prior to final plan approval and recorded on the deed.
- The cul-de-sac turnaround shall have a right-of-way radius of fifty-five (55) feet and an outer paving radius of forty-five (45) feet. The moving lane around the center island shall have a paved width of twenty (20) feet.*
- The cul-de-sac turnaround shall have a maximum grade of four (4) percent. The minimum grade around the curbing shall not be less than one (1) percent.
*Note: These radii are only appropriate for a cul-de-sac with a center island. If the center island requirement were to be waived, the right-of-way and paved radius should be reduced to 50 feet and 40 feet respectively.
