Rural residential drives and field drives should normally conform to the type 1 design shown in Fig. 2.49 (Ref. 14). New drives should intersect the highway at an angle between 70 and 90°. In some cases, however, it may be necessary to retain existing drive angles that vary from these desirable angles.
If the project involves existing drives, the existing width is normally retained unless it is less than 12 ft (3.7 m). In that case, it should be widened to provide a 12-ft (3.7-m) throat width. In the case of new drives, the width should normally be 12 ft (3.7 m). If the new driveway is a combined drive between two properties, the width should normally not exceed 24 ft (7.3 m). Also, a wider field drive may be used if it will keep a farm equipment operator from encroaching on the opposing traffic lane when entering or exiting the highway.
The radius of the type 1 driveway should normally be 25 ft (7.6 m). The radius may be increased on field drives if it is deemed that the larger values will improve driveway operation and reduce the hazard to motorists and farm equipment operators.
Driveways abutting uncurbed highways may be curbed. However, the curb should not extend closer to the through pavement edge than 8 ft (2.4 m) or the treated shoulder width, whichever is greater. This is recommended to avoid curb obstruction for vehicles, snowplows, etc., using the shoulder.
