Sleeper Types – Railway General Knowledge Capsule

1. Definition & Purpose

• Sleeper (US: Tie) is a transverse member laid below rails to:
  • Transfer wheel loads to ballast & formation
  • Maintain correct gauge & alignment
  • Provide elastic medium between rail & ballast
  • Facilitate track circuiting & return current path (in electrified sections)

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2. Classification of Sleepers on Indian Railways

Broad Group	Sub-type	Material	Key Standard	Typical Life	Use on IR
Wooden	Hardwood & Softwood (Sal, Teak, Deodar, Casuarina)	Timber	RDSO T-12-2001	12–15 yrs	≤ 10 % of total; mainly in approach of bridges, points & crossings
Steel	CST-9, Steel trough, 2-piece plate, Yoke plate	Mild steel	IRS-T-32-2008	35–40 yrs	< 1 %; limited to bridges & special locations
Cast Iron	CST-9, CST-12, Two-block, Plate sleeper	Cast iron	IRS-T-24-2008	35–40 yrs	< 1 %; obsolete except on girder bridges
Concrete	Mono-block (M-44, M-46), Two-block, T-5 post-tensioned, Pre-stressed (PRC)	RCC, Pre-stressed concrete	IRS-T-39-2022 (latest 5th rev.)	50–60 yrs	~98 % of all new track since 1990
Composite/Plastic	Recycled HDPE + rubber filler	Waste plastic	RDSO S/N-183-2019 Pilot	40 yrs (lab)	Trial on 3 km section (WR) as on 2023

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3. Technical Specifications (Latest IRS)

A. Pre-stressed Mono-block Concrete Sleeper (M-46 profile)

• Density      2,560 kg/m³
• Weight       280 kg (±5 kg)
• Length       2,750 mm (BG)
• Width at rail seat   280 mm
• Depth at centre    205 mm
• 28-day characteristic strength 60 MPa (M-60 grade)
• Tensioning wires   7 mm φ high-tensile (1,570 MPa)
• Initial pre-stress   1,000 MPa (single stage tensioning)
• Elastic modulus   38 kN/mm²
• Track modulus offered 90–110 N/mm³ (higher than wooden)
• Lateral resistance  1.7 × wooden sleeper
• Design wheel load  32.5 t (32.5 tonne axle) @ 160 kmph
• Spacing (normal BG)  600 mm c/c (1,660 sleepers/km)
• Sleeper density   1,540–1,660 nos./km (LWR track 60 kg 92 UTS rail)

B. Wooden Sleeper

• Standard sizes BG: 2,750 × 250 × 130 mm
• Adzing: 125 mm wide × 13 mm deep; 1 in 20 inward cant
• 8 anti-creep / gauge holding fittings (dog spikes, fang bolts)
• Treatment: Copper-Chrome-Arsenic (CCA) 8–12 kg/m³ retention

C. Steel Trough Sleeper

• Rolled from 22 mm thick MS plate
• Weight: 85 kg; Length: 2,750 mm
• Gauge holding: By projecting lugs & key holes for loose jaws

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4. Historical Milestones

Year	Event
1853	First IR track (Bombay–Thane) – Imported wooden (Jarrah) sleepers
1925	Steel trough sleepers adopted on girders of GIPR
1930	CST-9 cast iron sleeper designed by “Concrete Steel & Timber Co.”
1956	Indian Standard sleeper sizes codified (IS: 1138)
1966	First experimental PRC sleeper plant set up at Allahabad (MFP)
1974	Mono-block PRC sleeper regularised on 25 kV AC electrified track
1983	Pandrol clip introduced with PRC sleeper (RDSO T-39)
1987	Indigenous production of 60 kg rails & matching M-46 sleepers
1995	Decision: All new BG track to be with PRC sleepers only (except bridges)
2016	1st trial of composite recycled plastic sleeper (WR)
2022	5th revision of IRS-T-39 (permitting 60 kg & 52 kg rail on same sleeper)

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5. Current Status (2023-24)

• Total route km on Indian Railways: 68,043 km
• Total sleepers: ≈ 115 crore (1.15 billion)
• Share of concrete sleepers: 96.8 %
• Sleeper plants: 22 (16 MOF – Ministry-owned, 6 private)
• Annual capacity: 2.8 crore PRC sleepers
• Green initiative: 1.2 crore wooden sleepers saved per year by PRC switch-over
• Plastic sleeper pilot: 3 km (Virar–Dahanu) under monitoring; RDSO report due 2024
• Next-gen: 250 kmph capable “H-sleeper” (pre-stressed) under development by RDSO

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6. Comparative Advantages

Parameter	Wooden	Steel	Cast Iron	Concrete	Composite
Initial cost	Medium	High	Medium	Low	High
Track modulus	Low	High	Medium	Very high	Medium
Maintenance	High	Medium	Medium	Very low	Very low
Scrap value	Nil	High	High	Nil	Medium
Fire resistance	Poor	Good	Good	Excellent	Good
Corrosion	Bio-decay	Rust	Rust	Alkali-silica	UV-degradation
Handling	Easy	Heavy	Brittle	Heavy (280 kg)	Light (165 kg)

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7. Quick Facts to Memorise

• “Sleeper density” is expressed as number of sleepers per km (NOT per mile).
• Heaviest sleeper on IR: Pre-stressed concrete M-46 (280 kg).
• Longest lasting: PRC (50-60 yrs) → almost 2× CI/Steel.
• Eco-friendly: Every PRC sleeper saves ~0.07 m³ of forest wood.
• Standard packing: 50 sleepers per rake (stack height 1.8 m).
• White patch on PRC sleeper → indicates pre-stressing zone (tensioned).
• Blue stripe on side → 60 kg rail seat; Red stripe → 52 kg rail seat (new coding).

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8. 15+ MCQs (Railway Exam Pattern)

Which sleeper type offers the highest track modulus? A) Wooden sleeper B) Steel trough sleeper C) Cast iron sleeper D) Pre-stressed concrete sleeper

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Correct Answer: D Explanation: Pre-stressed concrete (PSC) sleepers provide the highest track modulus due to their weight and rigidity, ensuring superior track stability.

The weight of a standard BG pre-stressed concrete sleeper (M-46/RT-2496) is approximately? A) 180 kg B) 230 kg C) 280 kg D) 350 kg

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Correct Answer: C Explanation: A standard Broad Gauge (BG) pre-stressed concrete sleeper weighs approximately 280 kg, contributing to the lateral stability of the track.

Indian Railways decided in 1995 that all new BG tracks would be laid only with which sleeper? A) Steel sleeper B) Pre-stressed concrete sleeper C) Composite sleeper D) Cast iron sleeper

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Correct Answer: B Explanation: In 1995, Indian Railways standardized the use of Pre-stressed Concrete (PSC) sleepers for all new track construction and renewals on BG routes.

Which chemical treatment is specified for wooden sleepers on Indian Railways? A) Creosote oil B) Copper-Chrome-Arsenic (CCA) C) Pentachlorophenol D) Zinc chloride

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Correct Answer: B Explanation: Copper-Chrome-Arsenic (CCA) is the standard preservative treatment used to protect wooden sleepers from decay and termites.

The first experimental PRC sleeper plant of Indian Railways was set up at? A) Allahabad (Subedarganj) B) Lucknow C) Itarsi D) Secunderabad

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Correct Answer: A Explanation: The first experimental factory for producing Pre-stressed Reinforced Concrete (PRC) sleepers was established at Subedarganj, Allahabad (now Prayagraj).

What is the spacing of sleepers for BG LWR track with 60 kg rail? A) 550 mm B) 600 mm C) 650 mm D) 700 mm

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Correct Answer: B Explanation: For Long Welded Rail (LWR) on Broad Gauge with 60 kg rails, the standard sleeper spacing is 600 mm centre-to-centre (1660 sleepers per km).

Which sleeper is also known as the “CST-9” sleeper? A) Steel trough sleeper B) Wooden sleeper C) Cast iron pot sleeper D) RCC sleeper

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Correct Answer: C Explanation: The CST-9 (Central Standard Track No. 9) is a classic cast iron pot sleeper design formerly used extensively on Indian Railways.

The white paint patch on the side of a PRC sleeper indicates? A) Manufacturing date B) Rail seat area C) Zone of pre-stressing (tensioned wires) D) Defective sleeper

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Correct Answer: C Explanation: A white paint patch is applied to indicate the location of high-tension pre-stressing wires to prevent accidental damage during handling.

As per the latest IRS-T-39 revision, the minimum 28-day compressive strength of concrete for PRC sleeper is? A) 45 MPa B) 52 MPa C) 60 MPa D) 75 MPa

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Correct Answer: C Explanation: The specification requires M-60 grade concrete, which must achieve a minimum compressive strength of 60 MPa after 28 days.

Which of the following sleeper types is the heaviest? A) Steel trough sleeper B) Wooden sleeper C) Pre-stressed concrete sleeper D) Cast iron pot sleeper

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Correct Answer: C Explanation: Pre-stressed concrete sleepers are significantly heavier than other types, which helps in maintaining track geometry and ballast grip.

The trial stretch of recycled plastic composite sleeper on Western Railway is located between? A) Mumbai – Virar B) Virar – Dahanu C) Ahmedabad – Vadodara D) Surat – Valsad

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Correct Answer: B Explanation: A 3 km trial stretch using eco-friendly recycled plastic composite sleepers was implemented between Virar and Dahanu on the Western Railway.

Which sleeper requires “adzing” of the rail seat? A) PRC sleeper B) Steel sleeper C) Wooden sleeper D) Cast iron sleeper

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Correct Answer: C Explanation: Adzing is the process of cutting a slope into the rail seat of a wooden sleeper to provide the required inward rail cant.

The lateral resistance of a PRC sleeper is about how many times that of a wooden sleeper? A) 1.2 times B) 1.5 times C) 1.7 times D) 2.5 times

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Correct Answer: C Explanation: Due to its weight and shape, a concrete sleeper offers approximately 1.7 times more lateral resistance compared to a standard wooden sleeper.

Which sleeper type is prohibited in new track on Indian Railways except in bridges & special locations? A) Composite sleeper B) Steel sleeper C) PRC sleeper D) Rubber sleeper

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Correct Answer: B Explanation: Steel trough sleepers are generally prohibited for new main line track construction due to corrosion issues and lack of elasticity, except for specific bridge use.

The standard length of a BG wooden sleeper is? A) 2500 mm B) 2750 mm C) 3000 mm D) 3250 mm

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Correct Answer: B Explanation: The standard length for a Broad Gauge wooden sleeper is 2750 mm (9 feet).

“Sleeper density” 1540 M means? A) 1540 sleepers per mile B) 1540 sleepers per km C) 1540 mm spacing D) 1540 kg per sleeper

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Correct Answer: B Explanation: Sleeper density is expressed as the number of sleepers per kilometre of track (e.g., 1540 or 1660 per km).

Which colour stripe on a new PRC sleeper indicates suitability for 60 kg rail? A) Yellow B) Green C) Blue D) Red

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Correct Answer: C Explanation: A blue stripe on the side of a concrete sleeper indicates that it is specifically designed to accommodate 60 kg rail sections.

The approximate life of a steel trough sleeper on Indian Railways is? A) 15-20 years B) 25-30 years C) 35-40 years D) 50-60 years

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Correct Answer: C Explanation: Under normal conditions, a steel trough sleeper has a service life of approximately 35 to 40 years before requiring replacement.