Highway Engineering

Geometric Alignment and Design 159

A∞

X

Y

B∞

C∞

Bendiness = (A+B+C)∞∏(Distance X to Y in km)

Figure 6.5Estimation of bendiness.

0

Alignment constraint Ac (km/hr)

Mean speed of light vehicles (km/hr)

120

100

85

70

60

120A

120B

100A

100B

85A

85B

70A

70B

Design speed

(km/hr)

Layout constraint Lc (km/h)

24 6 8101 214161820

100

90

80

70

60

V 50 wet V 85 wet

5

10

15

20

25

30

35

Figure 6.6Chart for deriving design speeds (rural highways) (source: TD 9/93 (DoT, 1993)).