One liners - Transportation Engineering for GATE, PSUs - Part 4

Hello There,
I am here to give you another round of one liners from Surveying, for your preparation for GATE and PSUs.

• For a constant value of co-efficient of lateral friction, the value of required super-elevation increases with, increase in speed and with decrease in radius of curve.
• To calculate minimum value of ruling radius of horizontal curves in plain, the design speed is given by 16 kmph.
• The attainment of super-elevation by rotation of pavement about the inner edge of the pavement avoids the drainage problem in the flat terrain.
• Psychological extra widening of pavement depends upon the speed of the vehicle.
• In case of hill roads the extra widening is generally provided on the inner side of the curve.
• The mechanical widening required for a n lanes road is given by   (nl^2)/2R where, l is the length of wheel base of vehicle in meters.
• As per the recommendation of IRC, spiral curve is used as the transition curve in the horizontal alignment of the highways.
• The lower among the values obtained on the basis of allowable rate of change of centrifugal acceleration and based on rate of change of super-elevation, is taken as the design length.
• The maximum design gradient for vertical profile of a road is ruling gradient.
• The camber of a road should be approximately equal to half the longitudinal gradient.
• A cubic parabola is preferred in a valley curve.
• The value of ruling gradient in plains as per the recommendation of IRC is 1 in 30.
• Highway facilities are designed for thirtieth highest hourly volume.
• Enoscope is used to find the spot speed.
• For highway geometric design purposes the speed used is 98th percentile.
• Traffic capacity should always be greater than the traffic volume.
• Length of a vehicle affects extra width of pavements and minimum turning radius.
• The maximum width of a vehicle as per the recommendation of IRC is 2.44 m.
• Desire lines are plotted in origin and destination studies.
• License plate method is preferred for collecting origin and destination data for a small area like a mass business centre or a large intersection.

Thanks for visiting!

Reference: Civil Engineering Objectives by S P Gupta and S P Gupta.