Module 2: Geometric design of highways

Lecture 13 Sight distance

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The acceleration values of the fast vehicle depends on its speed and given in Table 1.

Table 1: Maximum overtaking acceleration at different speeds

Speed	Maximum overtaking
(kmph)	acceleration (m/sec$^2$)
25	1.41
30	1.30
40	1.24
50	1.11
65	0.92
80	0.72
100	0.53

Note that:

• On divided highways, $d_3$ need not be considered
• On divided highways with four or more lanes, IRC suggests that it is not necessary to provide the OSD, but only SSD is sufficient.