Transportation Engineering (Highways, Bridges, Traffic)
Transportation Engineering covers highway geometric design, pavement materials and design, traffic flow, intersections and bridges. IRC codes are central: IRC:37 for flexible pavements, IRC:38 for rigid pavements, IRC:86 for geometric design and IRC:106 for traffic.
Core rules
- Stopping sight distance SSD=0.278Vt+V²/(254f), with V in km/h and t in s.
- Superelevation e=V²/(127R)−f; e_max is 7% in plain terrain and 10% in hilly areas without snow.
- Extra widening at curves includes mechanical and psychological components.
- Flexible pavement design uses CBR and traffic in msa; rigid pavement uses slab thickness and axle-load stress.
- Traffic: PCU converts mixed vehicles; density=flow/speed; LOS uses volume-capacity ratio.
Worked example
V=80 km/h, t=2.5 s and f=0.35. SSD=0.278×80×2.5+80²/(254×0.35)=55.6+72.0=127.6 m. If the road has a gradient, the braking component changes and SSD must be adjusted. For a curve R=300 m, e=80²/(127×300)−0.15=0.168−0.15=0.018, so normal camber may suffice; check minimum and maximum limits.
Traps
- Using V in m/s in the SSD formula.
- Taking f=0.35 for all speeds; IRC values vary.
- Confusing superelevation with camber.
- Using design traffic in cv/day instead of msa.
- Ignoring gradient in SSD.