Monday, December 30, 2013

One liners - Transportation Engineering for GATE, PSUs - Part 5

Hello there,
How have you been? Here is another round of one liners for your preparation for the GATE and PSUs examinations.

  • The diagram which shows the approximate path of vehicles and pedestrian involved in accidents is known as collision diagram.
  • With increase in the speed of the traffic stream, the minimum spacing of vehicles increases.
  • Traffic volume is equal to  traffic density * traffic speed.
  • Practical capacity is also known as design capacity.
  • With increase in speed of the traffic stream, the maximum capacity of the lane first increases and then decreases after reaching a maximum value at optimum speed.
  • Equivalent factor of passenger car unit(PCU) for a passenger car as per IRC is 1.0.
  • Scientific planning of transportation system and mass transit facilities in cities should be based on origin and destination studies.
  • The diagram which shows all important physical conditions of an accident location like roadway limits, bridges, trees and all details of roadway conditions is known as condition diagram.
  • When the speed of traffic flow becomes zero, then traffic density attains a maximum value whereas traffic volume becomes zero.
  • On a right angled road intersection with two way traffic, the total number of conflict points is 24.
  • The background of informatory  sign board is yellow.
  • Level crossing is indicated by a warning sign.
  • "Dead Slow" is a regulatory sign.
  • The most efficient traffic signal system is flexible progressive system.
  • The provision of traffic signals at inter-sections reduces right angled collisions but may increase rear end collisions.
  • Stop or red time of a signal is the sum of go and clearance for the cross flow.
  • Clearance time is generally 3 to 5 seconds.
  • The cycle length is normally 40 to 60 seconds for two phase signals.
  • Centre line markings are used in roadways meant for two way traffic.
  • The particular places where pedestrians are to cross the pavement are properly marked by the pavement marking known as crosswalk lines.
  • The entrance and exit curves of a rotary have different radii and different widths of pavement.
  • When two equally important roads cross roughly at right angles, the suitable shape of central island is circular.
  • Beyond 5000 vehicles per hour the rotary may not function efficiently.

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

Tuesday, December 24, 2013

One Liners/MCQs- Transportation Engineering.- part 3


Here are few MCQs which might help you with Transportation Engineering.
For more you can write below in the comment box or join my Facebook Page.

1. The camber preferred in concrete roads is

(a) Parabolic Camber
(b) Straight Camber
(c) Combination of parabolic and straight camber
(d) Cubic

Ans: (b) Straight

2. The shoulders are preferred to be

(a) Paved
(b) Rough
(c) Smooth

Ans: (b)

3. To avoid overturning and lateral skidding, the centrifugal ratio and lateral friction must be 
(a) Equal to b/2h
(b) More than b/2h
(c) Less than b/2h
(d) 0
  where b is the wheel base and h is the height of the center of gravity.
Ans: (c)

4. When the longitudinal distance covered is more than the wheel circumferential distance, this phenomenon is called:
(a) Sliding
(b) Skidding
(c) Overturning
(d) Decelerating
Ans: (b)

5. Nagpur road plan was based on 

(a) Star/Radial Road Pattern
(b) Rectangular road pattern
(c) Star/Radial and rectangular road pattern
(d) Star and Grid Pattern

Ans: (d)

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