F. - Vertical Geometrics—Driveway Grade Change (Commercial Driveways Only).

Access driveways on arterial roadways shall always be designed to allow vehicles to proceed into or out of the driveway at a speed that will prevent large speed differentials between turning and through traffic. Required apron lengths, desirable grade changes and maximum allowable grade changes are shown in the table below. The apron is a relatively flat area where the driveway meets the public roadway. These guidelines apply to all types of driveways, including for residential, commercial and industrial uses. Driveways shall always have a minimum grade change between ½ to 1 percent to provide for adequate drainage. Either an upgrade or downgrade is permissible.

Desirable grades and maximum allowable grades are shown in the following table. Driveways should have a minimum grade of 1% for drainage.

Roadway Classification	Required Minimum Apron Length ("A" in the Diagram)	Desirable Grade Change	Maximum Grade Change Allowed
Principal Arterial	25-30 feet	[2%-3%]	[3%-4%]
Minor Arterial	20 feet	[4%]	[5%]
Collector	15 feet I	[5%]	[6%]

 

Notes: NA: No driveways are allowed on this classification. The Apron Length is shown as "A" and grade change as "D" on the diagram below. The grade may change along the course of the driveway, as indicated by G1 and G2. In such cases, it is very important to ensure that the minimum apron length is maintained.