Table 6.4. GDOT Design Standards for Freeways

Item No.

Item

Rural

Urban

1

Design Speed (mph)(1)

70

55

65

2

Level of Service (LOS)

B (2)

C(3)

C (3)

3

Number of Travel Lanes(4)

6

6

6

4

Width of Travel Lanes

12-ft.

12-ft.

12-ft.

5

Overall Width of Shoulders

     Outside

14-ft.

14-ft.

14-ft.

     Inside(5)

12-ft.

12-ft.

12-ft.

6

Width of Paved Shoulders

   Outside

12-ft.

12-ft.

12-ft.

   Inside(5)

10-ft.

10-ft.

10-ft.

7

Width of Median (ft)

    Depressed

52 - 64

n/a

n/a

    Continuous Barrier (6 lane)

n/a

30 - 40

30 - 40

    Continuous Barrier (8 lane)

n/a

28 - 30

28 - 30

8

Fore Slope Ratio

4:1

4:1

4:1

9

Back Slope Ratio

2:1 max.

2:1 max.

2:1 max.

10

Pavement Cross Slope

0.02-ft./ft.

0.02-ft./ft.

0.02-ft./ft.

11

Stopping Sight Distance(6)

730-ft.

495-ft.

645-ft.

12

Maximum Superelevation

0.08-ft./ft.

0.06-ft./ft.

0.06-ft./ft.

13

Min. Radius with superelevation)(7)

1,810-ft.

1,060-ft.

1,660-ft.

14

Maximum Grade (%)(8)

    Level

3%

4%

3%

    Rolling

4%

5%

4%

    Mountainous

5%

6%

5%

15

Minimum Vertical Clearance (ft)(9)

16.75 - 17.5

16.75 -17.5

16.75 -17.5

16

Horizontal Clearance (from edge of travel lane)(10)

    4:1 Foreslope

n/a

36

n/a

    6:1 Foreslope

38

30

38

17

Minimum Width of Right-of-Way (ft)(11)

As needed

As needed

As needed

Notes:

(1) See current AASHTO Green Book, chapter 8, Design Speed. Also see notes 6,7, and 8 for design speeds not shown

(2) LOS C is permissible for urban conditions and auxiliary facilities in rural areas.

(3) LOS D is permissible in highly developed urban areas.

(4) Consider widening from existing 4 lanes to 6 lanes.

(5) On Freeways with six or more lanes and with truck traffic more than 250 vph, use 12-ft. inside shoulders.

(6) Values shown are for the given design speed. For other design speeds, refer to the AASHTOGreen Book, Chapter 3.

(7) Values shown are for the given design speed. For other design speeds, refer to the AASHTOGreen Book, Chapter 3.

(8) Values shown are for the given design speed. For other design speeds, refer to Chapter 4 of this Manual.

(9) Minimum values are for vehicular clearances. Please refer to the GDOT Bridge and Structures Design Policy Manual for further information, clearances at other facilities, and limitations.

(10) Minimum horizontal clearance equals to clear zone plus 4-ft. typical ditch.

(11) Refer to Section 6.10 for determination of width of required right of way.