Saturday, December 28, 2013

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.

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