One liners - Transportation Engineering for GATE, PSUs - Part 6

Hello there,

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

• A traffic rotary is justified where number of intersecting roads is between 4 to 7.
• When a number of roads are meeting at a point and only one of the roads is important, then the suitable shape of rotary is tangent.
• Maximum number of vehicles can be parked with 90 degree parking.
• When the width of kerb parking space and width of street are limited, generally preferred parking system is parallel parking
• As per IRC recommendations, the average level of illumination on important roads carrying fast traffic is 30 lux.
• The most economical lighting layout which is suitable for narrow roads is single side lighting.
• The direct interchange ramp involves diverging to the right side and merging from right.
• In soils having same plasticity index, if liquid limit is increased, then compressibility and permeability increases but dry strength decreases.
• Aim of the Impact test is to check the toughness of road aggregates.
• Los Angleles testing machine is used to find the abrasion value.
• In Dorry's abrasion test, Hardness = [20 - (loss in weight/3)].
• In CBR test the value of CBR is calculated at 2.5 mm and 5 mm penetrations.
• If impact value is between 20 to 30, aggregate is satisfactory for road surfacing.
• The maximum allowable Los Angeles abrasion value for high quality surface course is 30%.
• Percentage of free carbon in bitumen is less than that in tar.
• The ductility value of bitumen for suitability in road construction should not be less than 50 cm.
• The maximum limit of water absorption for aggregate suitable for road construction is 0.6%.
• Penetration test is performed to find out the grade of the bitumen.
• Bitumen of grade 60/70 means, its penetration value is 6 to 7 mm.
• The recommended grade of tar for grouting purpose is RT-5.
• Softening point of bitumen to be used for road construction at a place should be above the maximum temperature at that place.
• For rapid curing cut-backs gasoline is used as oil.
• As per IRC recommendations CBR method is preferred for design of flexible pavements.

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