Track Components – Railway GK for RRB & RPF Exams

Introduction

The permanent way (track) is an engineered structure consisting of rails, sleepers, ballast, fastenings and sub-grade, designed to safely guide and support trains. Every component has a defined load-transfer path and maintenance regime. A sound grasp of these details is essential for all technical & non-technical railway exams.

1. Rails

1.1 Function

• Provide a continuous, level and smooth rolling surface for wheels
• Transmit axle-load to sleepers and ultimately to formation

1.2 Types (Indian Railways)

1.3 Lengths

• Standard length = 13 m (BG), 12 m (MG), 11 m (NG)
• 260 m long-welded rails (LWR) & 780 m continuous-welded rails (CWR) are now standard on new lines

1.4 Wear Limits (per Indian Railways Permanent Way Manual 2021)

• Vertical wear ≤ 6 mm for 60 kg rail
• Side wear ≤ 8 mm
• 5 % loss in sectional weight calls for replacement

1.5 Rail Steel Chemistry

• C 0.55–0.75 %, Mn 0.8–1.1 %, Si 0.1–0.5 %
• UTS ≥ 880 MPa (72 kg/mm²) for 60 kg grade

2. Sleepers (Ties)

2.1 Functions

• Hold rails to correct gauge & inclination (1 in 20)
• Transfer train load to ballast and provide elasticity

2.2 Classification

1. Timber – Sal, Teak, Deodar (life 15–20 y)
2. Steel – CST-9 (9 plates), 90 kg; used in 1950-70
3. Cast Iron – Pot/Plate type (rare now)
4. Pre-stressed Concrete (PSC) – Mono-block, two-block, twin-block

2.3 PSC Sleeper Details (most common)

• Length: 2.60 m (BG), 1.80 m (MG)
• Weight: 285 kg
• Concrete grade: M-60
• High-tensile wire: 5 mm ϕ, 18–20 wires, initial tension 1000 MPa
• Spacing: 65 cm average (BG), 60 cm (MG)

2.4 Sleeper Density

• (n + 3) to (n + 7) sleepers per rail length (13 m)
• → 1540–1660 sleepers/km for BG main line

3. Ballast

3.1 Functions

• Resist longitudinal & lateral forces
• Provide immediate drainage and elasticity
• Distribute load to sub-grade

3.2 Specifications (IRS-GE-1 2016)

• Stone: Igneous (trap, basalt, granite) – 0 % flaky index > 35
• Size:
  • 50 mm to 20 mm (through-screened) for main line
  • 20 mm to 40 mm (retained on 40 mm < 5 %)
• Depth under sleeper: 250 mm (BG), 200 mm (MG)
• Clean ballast cushion: 300 mm below bottom of sleeper for heavy-haul routes

3.3 Ballast Profile

• Shoulder width: 300 mm (minimum)
• Top of formation (TOF) width: 6.85 m (BG, single line)

4. Rail Fastenings

4.1 Elastic Rail Clip (ERC)

• Mark-III free height 200 mm, toe-load 710 kg
• Mark-IV free height 210 mm, toe-load 900 kg (LWR/CWR)
• Pandrol “e-Clip” (imported) 1300 kg toe-load; used in DFC & HSR

4.2 Base Plate & Rubber Pad

• 6 mm thick micro-cellular EVA pad reduces impact by 30 %

4.3 Cotters & Keys

• Keys are driven 1 in 30; split cotter (for fish-plates) is of mild steel 12 mm ϕ

4.4 GM (Gauge-Maintaining) liners used with ERC to adjust gauge ± 1 mm

5. Fish-Plates & Bolts

• Section: 4-hole (52 kg/60 kg) or 6-hole (90 R)
• Material: M-44 steel (0.4 % C)
• Bolt torque: 640 N-m
• Expansion gap: 6 mm at 35 °C for 13 m rail (fish-plated)

6. Sub-Grade & Formation

6.1 California Bearing Ratio (CBR) value required

• ≥ 8 % for BG main line
• ≥ 4 % for MG/NG

6.2 Blanketing Layer (BL)

• 300 mm thick blanket of coarse-grained soil (GP, GW) below ballast to cut capillary rise

7. Historical Milestones

• 1853: First 53 km BB&CI line – 42 lb/yd flat-footed rails on timber sleepers
• 1922: Indian Railway Standard (IRS) rail sections codified
• 1957: Decision to adopt 52 kg rail for all BG routes
• 1990s: Switch to 60 kg 90 UTS rail for Dedicated Freight Corridor planning
• 2006: First 1 km trial of ballast-less track (RHEDA 2000) on Faridabad–New Delhi section
• 2021: Indian Railways approves Head-Hardened (HH) 60 kg rail (350 BHN) for DFC

8. Current Status & Recent Updates

1. Indian Railways procures only 60 kg/52 kg HH rails from SAIL (BSP, DSP)
2. 100 % mechanised deep-screening & tamping with CSM, UNIMAT & UNOMAT machines
3. Complete switch to PSC sleepers: Timber now < 0.5 % of inventory
4. Green Initiatives:
   • Recycled rubber pads from end-of-life tyres
   • Blast-furnace slag ballast trial on 41 km of ECoR
5. Ballast-less Track (BLT):
   • 508 km of Mumbai–Ahmedabad HSR will use Japanese slab-track (RAF-N)
   • BLT standard being finalised by RDSO for 160 km/h semi-urban routes (Draft 2023)
6. Corrosion-resistant Cu–Cr–V alloy rails (SAIL ZINCREX) under trial; targeted life 50 years

9. Summary Tables for Quick Revision

A. Rail Comparison

B. Sleeper Spacing vs Speed

10. Practice MCQs

1. What is the standard length of a BG rail in Indian Railways? A) 12 m B) 13 m C) 15 m D) 26 m

   Show Answer

   Correct Answer: B Explanation: The standard length for a single Broad Gauge (BG) rail used on Indian Railways is 13 metres.

2. Which rail section is presently adopted for all new Dedicated Freight Corridor tracks? A) 52 kg B) 90 R C) 60 kg D) 65 kg

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   Correct Answer: C Explanation: The 60 kg rail section is the standard for high-axle load tracks like the Dedicated Freight Corridors (DFC).

3. The minimum depth of ballast cushion below the bottom of sleeper for BG is? A) 250 mm B) 150 mm C) 200 mm D) 300 mm

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   Correct Answer: A Explanation: A minimum ballast cushion of 250 mm is required for Broad Gauge tracks to ensure adequate load distribution and drainage.

4. Mark-IV elastic rail clip provides a toe-load of approximately? A) 600 kg B) 900 kg C) 1050 kg D) 1200 kg

   Show Answer

   Correct Answer: B Explanation: The ERC Mark-IV is designed to provide a nominal toe-load of approximately 900 kg to hold the rail firmly.

5. Pre-stressed concrete sleepers are manufactured with concrete grade? A) M-35 B) M-45 C) M-50 D) M-60

   Show Answer

   Correct Answer: D Explanation: High-strength M-60 grade concrete is used for manufacturing PSC sleepers to withstand heavy axle loads and vibrations.

6. Which sleeper type is obsolete on Indian Railways and has been replaced by PSC? A) Steel CST-9 B) Composite Sleeper C) Wooden Sleeper D) Bridge Sleeper

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   Correct Answer: A Explanation: Steel CST-9 and other cast iron sleepers are now considered obsolete for main lines and have been replaced by Pre-stressed Concrete (PSC) sleepers.

7. The shoulder width of ballast on each side of the track should not be less than? A) 150 mm B) 200 mm C) 300 mm D) 450 mm

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   Correct Answer: C Explanation: For stability, especially in LWR (Long Welded Rail) territory, the ballast shoulder width must not be less than 300 mm.

8. Maximum permissible vertical wear for 60 kg rail (in mm) is? A) 4 B) 6 C) 8 D) 13

   Show Answer

   Correct Answer: B Explanation: As per the Permanent Way manual, the maximum vertical wear permitted for 60 kg rails is 6 mm.

9. Which of the following is NOT a function of ballast? A) Providing elasticity to the track B) Holding sleepers in position C) Facilitating drainage D) Providing electrical insulation between two rails

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   Correct Answer: D Explanation: Ballast provides stability, drainage, and elasticity; however, electrical insulation is provided by rubber pads and liners, not the ballast itself.

10. The expansion gap provided at 35 °C for a 13 m fish-plated rail is? A) 6 mm B) 2 mm C) 4 mm D) 10 mm

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    Correct Answer: A Explanation: For a standard 13 m rail length at a mean temperature of 35 °C, a 6 mm expansion gap is typically provided.

11. Two-block reinforced concrete sleeper was first tried in India during? A) 1940s B) 1950s C) 1960s D) 1980s

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    Correct Answer: C Explanation: The two-block (RCC) sleepers were first introduced on a trial basis in India during the 1960s before transitioning to mono-block PSC.

12. Head-hardened rails have a Brinell hardness number (BHN) of about? A) 250 B) 350 C) 450 D) 600

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    Correct Answer: B Explanation: Head-hardened (HH) rails are treated to reach a hardness of approximately 350 BHN to resist wear on curves and high-traffic routes.

13. Which machine is used for mechanised tamping and lining of track? A) BCM B) BRM C) DTS D) UNIMAT

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    Correct Answer: D Explanation: UNIMAT machines are specialized tampers used for the mechanized leveling, tamping, and lining of track, including points and crossings.

14. The minimum CBR value required for sub-grade of BG main line is? A) 5 % B) 8 % C) 12 % D) 15 %

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    Correct Answer: B Explanation: A minimum California Bearing Ratio (CBR) value of 8% is required for the sub-grade to ensure adequate soil stability for BG main lines.

15. The weight of a standard BG PSC sleeper is approximately? A) 150 kg B) 235 kg C) 285 kg D) 350 kg

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    Correct Answer: C Explanation: A standard mono-block pre-stressed concrete sleeper for Broad Gauge weighs approximately 285 kg.

16. Which type of rail clip is used in the ballast-less track of Mumbai–Ahmedabad HSR project? A) Pandrol e-Clip B) ERC Mark-III C) Vossloh System D) Mark-V

    Show Answer

    Correct Answer: A Explanation: The High-Speed Rail (HSR) project utilizes specialized fastening systems, with Pandrol e-Clips being a primary component for ballast-less track stability.

Last Updated: January 2026