Transportation Engineering (General Engineering) (SSC JE)

Figure
• In highway geometric design cumulative speed distribution is drawn and design is checked at 98th percentile.
• 98th percentile speed–It is the speed at or below which 98% of vehicle are moving.
• 85th percentile speed–It is the speed at or below which 85% of vehicle are moving.
• 15th percentile speed–It is the speed at or below which 15% of vehicle are moving.
• It is taken as lower limit of speed.

Classification of pavement marking–
1. Longitudinal marking (LM)
2. Transverse marking (TM)
3. Hazard marking (HM)
4. Block marking (BM)
5. Arrow marking (AM)
6. Directional marking (DM)
7. Facility marking (FM)
Line marking–
1. Center line
2. Warning line
3. Edge line
4. No-overtaking line
• It is applied to various situations like undivided road, divided carriageway roads and one way street/ramp/slip roads.
• The center lines should be used only on single carriageway rods to separate the opposite streams of traffic and to facilitate their movements.

C.B.R. standards for crushed stone during testing–
Value of load
C.B.R. (California Bearing Ratio)–CBR is used to determine the material properties for pavement design.
• Maximum value of CBR for any material is 100.
• The pressure upto a penetration of 12.5 mm and its ratio to the bearing value of a standard crushed rock is termed as the CBR.
• In most cases CBR decreases as thie penetration increases.

The aggregates crushing value gives a relative measure of resistance of an aggregate to crushing under gradually applied compressive load. This test is conducted on single sized aggregate passing 12.5 mm sieve and retained on 10 mm sieve. The aggregate is tested in a surface dry condition.
• The approaches is filled with 3 layers of aggregate and each layer is tamped 25 stocks by the rounded end of tamping rod. 40 tonnes of load is applied at a rate of 4 tonnes/minute.
Aggregate crushing value–

• A value less than 10 shows strong aggregate while above 35 shows weak aggregate.
• For the bituminous concrete a maximum value of 35 is specified.
• A maximum value of 40% is allowed for WBM base course in Indian conditions.

• It is resistance of flow or measurement of hardness of bitumen.
• Distance penetrate is sample by a standard pointed needle at 25ºC when a 100 gm of load is applied for 5 days.
• Unit of penetration is 1/10 mm.
• Therefore 80/100 means penetration of 8-10 mm
• Penetration grade 30/40 to use roads with high volume of traffic.
• Penetration 60/70 to use superior type of roads with high traffic in normal summer temperature.
• Cut back bitumen is used to premix and surface dressing in cold weather condition.
• Emulsion is used to wet condition (rainy season) maintenance work etc.

Average speed of vehicles over a certain road length at any time. It is the harmonic mean of the speed.
Given–
Number of vehicle η = 5
All vehicle are moving with a speed = 80 kmph

Given that,
Observed time mean speed (Vₜ) = 65 kmph Standard deviation of observed time mean speed ( = 8.06

Given that–
The number of vehicles–
600, 450, 500, 575, 610 and 388.
Observed in successive 10 min periods
Find–
traffic volume - ?
Flow rate - ?
Traffic volume = 600 + 450 + 500 + 575 + 610 + 388

• Load transfer device across transverse joint and they keep the two slab at same height.
• Load transfer capacity of the dowel bar is assumed to be 40% of the wheel load.
• Spacing between dowel bars is kept at 30 cm.
• Length between 40 cm to 73 cm nearly 60 cm.
• Diameter of bar varies between 20 mm to 30 mm.
• Mild steel round bars are bonded at one end but the other side is kept free.
• Stresses in dowel bar are given by pradbury analysis.
• Dowel bar are not provided for slab thickness less than 150 mm.
• Man load transferred through dowel bar is 40% of man axle load.