Table 4.4. Turn Lane Transition Tapers

Design Speed (mph)

Urban or Rural

Median Width (ft.)

Transition Width, W (ft)

Minimum

Desirable

Left Turn

Right Turn

Left Turn

Right Turn

Taper Ratio

Taper Length (ft.)

Taper Ratio

Taper Length (ft.)

Taper Ratio

Taper Length (ft.)

Taper Ratio

Taper Length (ft.)

Type A Median

> 45

Rural

40

12

8.33:1

100

8.33:1

100

15:1

180

15:1

180

> 45

Rural

44

12

8.33:1

100

8.33:1

100

15:1

180

15:1

180

> 45

Rural

64

12

8.33:1

100

8.33:1

100

15:1

180

15:1

180

Type B Median

> 45

Rural

32

4

15:1

60

8.33:1

100

15:1

60

15:1

180

> 45

Rural

44

16

15:1

240

8.33:1

100

15:1

240

15:1

180

> 45

Rural

64

26

15:1

390

8.33:1

100

15:1

390

15:1

180

Type C Median

< 45

Urban*

20

12

5:1

60

8.33:1

100

15:1

180

15:1

180

Flush Median

> 45

Rural

14

14

8.33:1

116

8.33:1

100

15:1

210

15:1

180

> 45

Rural

Varies

14

8.33:1

116

8.33:1

100

15:1

210

15:1

180

* An urban section with a Type C Median can be used for design speeds of 45 mph