If the centrifugal ratio is given and comfort conditions hold good, the length of transition curve L for roads will be (where R is radius.)
- A16·52 √R
- B12·80 √RCorrect
- C8·80 √R
- D4·52 √R
Solution
Concept
Empirical formula for the transition curve length
Formula
L = 12.80 √R (plain and rolling terrain, IRC)
Step-by-step solution
1. IRC gives the minimum length of a transition curve from the comfort criterion: L = 12.80 √R for plain and rolling terrain. 2. For mountainous and steep terrain the smaller value L = 4.52 √R... is permitted.
Explanation
The empirical IRC formula follows from limiting the rate of change of centrifugal acceleration to a comfortable value; 12.80√R is the value for plain and rolling terrain.
Why the other options are wrong
16.52 and 8.80 are not IRC coefficients. 4.52 √R applies to mountainous terrain.
Shortcut
L = 12.8 √R (plain), 4.5√R... (hilly).
Common mistake
Mixing the terrain values.
Correct answer: B) 12·80 √R