IRC 3:2021 is the Indian Standard (IRC) for dimensions and weights of road design vehicles (fifth revision). IRC 3 defines the dimensions, weights, and envelope of road design vehicles used across every Indian traffic and road engineering decision. The 2021 revision (5th edition) modernized the design vehicle fleet — added multi-axle articulated trucks up to 49 tonnes, updated container semi-trailer envelope to 4.75 m height, and refined turning radii. Every bridge designer uses IRC 3 to verify vertical clearance. Every road engineer uses it to design lane widths and curves. Every pavement engineer uses IRC 3 axle loads as input to IRC 37 flexible pavement M-E analysis and IRC 58 rigid pavement design. It is the Indian equivalent of AASHTO's design vehicle chapter — the dimensional reference that keeps every other road/bridge code internally consistent.
Specifies standard dimensions, axle loads, gross vehicle weights, and envelope of motor vehicles used as design reference for road geometry, pavement design, bridge loading, and clearance verification across Indian roads and highways.
Standard road design vehicle dimensions, weights and axle loads used for geometric and pavement design.
| Reference | Value | Clause |
|---|---|---|
| Max overall vehicle width — single deck— CMVR 1989 Rule 93 reference | 2.6 m | Cl. 3.2.1 |
| Max overall vehicle height — single deck (rigid) | 3.8 m | Cl. 3.2.2 (a) |
| Max overall vehicle height — double deck bus | 4.75 m | Cl. 3.2.2 (b) |
| Max overall length — single rigid 2-axle truck/bus | 12.0 m | Cl. 3.2.3 (a) |
| Max overall length — articulated tractor-semitrailer | 18.75 m | Cl. 3.2.3 (b) |
| Max overall length — truck-trailer combination | 18.75 m | Cl. 3.2.3 (c) |
| Max axle load — single steering axle | 7.5 t | Cl. 4.2.1 (a) |
| Max axle load — single drive (dual tyre) axle | 11.5 t | Cl. 4.2.1 (b) |
| Max axle load — tandem axle | 21.0 t (rigid) / 19.0 t (articulated) | Cl. 4.2.2 |
| Max axle load — tridem axle | 27.0 t | Cl. 4.2.3 |
| Max gross vehicle weight (GVW) — 4-axle rigid | 30.5 t | |
| Max GVW — articulated 5-axle | 42.0 t | |
| Max GVW — articulated 7-axle (tractor + semitrailer) | 55.0 t | |
| Min ground clearance — design vehicle | 300 mm (laden) | Cl. 3.1.5 |
| Min turning radius — single rigid 2-axle truck | 12.0 m (kerb-to-kerb) | |
| Min turning radius — articulated semi-trailer | 13.5 m (outer wheel) | |
| Design vehicle classes — number defined | Multiple classes (car, LCV, bus, 2/3/4/5/6/7-axle truck) | Cl. 3.1.1 |
| Tractor + 2 trailers (twin trailer) — max length | 25.25 m (special permit) | Table 3.2, Note 3 |
| Passenger car — typical design length × width | 4.7 m × 1.8 m | Annex A, Fig. A-1 |
| Bus — typical 2-axle (12 m) overhang front / rear | ≤ 3.0 m / ≤ 3.5 m |
IRC 3 (Fifth Revision, 2021) provides Dimensions and Weights of Road Design Vehicles — the IRC's authoritative reference defining the physical dimensions + permissible gross + axle weights of vehicles to be considered in road + bridge design + traffic operations. The 2021 revision aligns with current Indian truck industry standards + Bharat Stage VI emission norms.
Use IRC 3 when you are: - Designing road geometry considering vehicle off-tracking + turning radius - Doing bridge load design per IRC:6:2017 (vehicle classes referenced in IRC 3) - Specifying truck restrictions on roads + bridges - Setting load + size limits for specific routes - Doing pavement design per IRC:37:2018 (vehicle damage factor based on IRC 3 axle loads) - Designing intersections, rotaries, lay-bys for design vehicle off-tracking - Evaluating over-dimensional vehicle (ODV) routes
What IRC 3 covers: - Vehicle classification (car, truck, MAV, special) - Maximum permissible dimensions (length, width, height) - Maximum permissible gross weight - Maximum permissible axle load (single, tandem, tridem) - Tyre pressure + contact area - Design vehicle for off-tracking + turning radius analysis - Special vehicle categories (LMV, bus, truck, articulated)
Why a separate dimensions + weights code? - Variable industry-wide truck specifications - Need for standardised design assumptions - Frequent revisions to capture changes in vehicle technology - Cross-reference base for IRC:6:2017, IRC:37:2018, IRC:38:1988, etc.
Vehicle classification (per IRC 3:2021):
1. Two-Wheelers (2W): - Motorcycle / scooter / moped - Length: 1.5-2.5 m - Width: 0.7-1.0 m - Height: 1.0-1.4 m - Weight: 90-300 kg
2. Three-Wheelers (3W): - Auto-rickshaw, cargo 3W, e-rickshaw - Length: 2.5-3.5 m - Width: 1.0-1.5 m - Height: 1.7-2.0 m - Weight: 350-900 kg
3. Light Motor Vehicles (LMV): - Car, jeep, taxi, MUV - Length: 3.5-5.5 m - Width: 1.5-1.9 m - Height: 1.5-2.0 m - Weight: 800-2,500 kg - Axle load: ≤ 7.5 tonnes
4. Light Commercial Vehicles (LCV): - Tempo, light truck, 7-9 seater van - Length: 5.0-7.0 m - Width: 1.8-2.2 m - Height: 1.8-2.5 m - Weight: 2,500-7,500 kg - Single axle load: ≤ 8.0 tonnes
5. Heavy Commercial Vehicles — Truck (HCV-T): - 2-axle truck, single rear (4×2) - Length: 7.0-9.0 m - Width: 2.0-2.6 m - Height: 2.5-3.5 m - Weight: 7,500-16,500 kg - Single axle: ≤ 10.2 tonnes; rear: ≤ 11.5 tonnes
6. Heavy Commercial Vehicles — 3-Axle: - 3-axle truck (6×2 or 6×4) - Length: 8.0-10.5 m - Width: 2.2-2.6 m - Height: 3.0-3.5 m - Weight: 16,500-25,500 kg - Tandem (rear): ≤ 19 tonnes
7. Multi-Axle Vehicles (MAV) — 4-Axle: - 4-axle truck (8×4 or 6×4 + 1) - Length: 9.0-12.0 m - Width: 2.4-2.6 m - Height: 3.0-3.8 m - Weight: 25,500-31,000 kg - Tandem axle (rear): ≤ 19 tonnes
8. Multi-Axle Vehicles (MAV) — 5+ Axle: - Articulated tractor-trailer - Length: 12.0-18.5 m (subject to ODV permit) - Width: 2.4-2.6 m - Height: 3.0-4.0 m - Weight: 35,000-50,000 kg (or higher for ODV) - Multiple tandems / tridems
9. Bus: - Mini-bus, standard bus, double-decker (rare) - Length: 6.0-12.0 m - Width: 2.2-2.6 m - Height: 3.0-3.5 m - Weight: 6,000-16,500 kg
10. Special vehicles: - Crane, tractor-trailer, dumper, fire engine, ambulance, military vehicles - Wide-load over-dimensional vehicle (ODV) — special permits
Maximum permissible axle loads (per Motor Vehicles Act + IRC 3:2021): - Single axle (single tyres): 6.0 tonnes - Single axle (dual tyres): 10.2 tonnes - Tandem axle: 19.0 tonnes - Tridem axle: 24.0 tonnes - **Special / Heavy: ODV permits up to higher values
Maximum permissible gross vehicle weight: - 2-axle truck: 16.5 tonnes - 3-axle truck: 25.0-25.5 tonnes - 4-axle truck: 31.0 tonnes - 5-axle articulated: 40.0-44.0 tonnes - 6+ axle articulated / heavy: 50+ tonnes
Maximum permissible dimensions: - Length: 12.0 m (rigid) / 18.5 m (articulated) standard; up to 20+ m with ODV - Width: 2.6 m standard; ODV allows up to 2.75 m - Height: 4.2 m maximum (must clear 5.0 m typical bridge clearance with margin)
Design vehicle for geometric design: - For off-tracking + turning radius: WB-12 (12 m wheelbase 2-axle truck) standard - For curves + intersections: WB-15 or WB-19 (longer wheelbase for accommodate over-tracking) - For premium / NH design: WB-21 (largest standard articulated) - For special routes: custom design vehicle per ODV evaluation
Tyre + contact area: - Standard tyre size: 9.00×20 or 10.00×20 standard truck tyres - Tyre pressure: 550 kPa (5.5 kg/cm²) typical for design - Tyre contact area: 200-300 cm² per tyre (single) - Tyre arrangement: dual tyres on heavy axles (better load distribution)
Bridge design implications (per IRC:6:2017): - Class A loading: 1.14 tonne wheel load (4 wheels in dual-tandem) - Class B loading: lighter; for narrow / rural bridges - Class 70R loading: heavy military / boom-mounted; for special situations - Vehicle classification: IRC 3 + IRC 6 cross-reference
Pavement design (per IRC:37:2018): - Vehicle Damage Factor (VDF): converts vehicle class to equivalent standard axle load (ESAL) - VDF values per vehicle class (typical Indian): - LMV: 0.0001 - LCV: 0.05-0.10 - 2-axle truck: 1.5-2.5 ESAL - 3-axle truck: 2.5-3.5 - 4-axle MAV: 3.0-4.0 - 5-axle articulated: 3.5-4.5 - Pavement design ESAL: AADT × VDF × growth × life
Geometric design (per IRC:38:1988): - Off-tracking: longer wheelbase vehicles track wider; required widening at curves - Extra widening table in IRC 38 calibrated for WB-12 design vehicle - Larger design vehicle (WB-19+): additional widening required
Intersection design (per IRC:SP-21:2009): - Turning radius: matched to design vehicle template - Sweep path: verified for largest expected vehicle - Sight distance: allows large-vehicle perception
Restrictions + enforcement: - Posted weight limit signs: per IRC 67 - Posted height limit signs: at low-clearance bridges - Weight enforcement: weighbridges + RTO - Over-dimensional permits: issued per IRC 3 + RTO clearance
1. Design vehicle too small for actual traffic. WB-12 used; actual traffic has WB-19 MAVs; off-tracking exceeds widening. Use realistic design vehicle. 2. Pavement designed for old VDF assumptions. Pre-2010 VDFs used; modern MAVs not represented; under-design. Use current IRC 37 VDF per IRC:37:2018 + IRC:3:2021. 3. Bridge designed for old load class. Pre-1996 IRC 6 used; modern MAVs exceed; bridge under-designed. Use current IRC:6:2017. 4. Off-tracking check skipped. Curve / intersection geometry assumed; actual large-vehicle off-tracking damages adjacent areas. Sweep-path check mandatory. 5. No allowance for ODV / heavy vehicles. Route used for ODV traffic; bridge / road under-designed; failures. Identify ODV routes; design accordingly. 6. Tyre pressure assumption wrong. Indian trucks often run higher pressure than 550 kPa; pavement damage accelerated. Verify actual tyre pressures. 7. Vehicle dimensions assumed; not verified. Pre-2021 dimensions used; current vehicles slightly larger. Use current IRC 3 specifications. 8. Width / height not verified at bridges. Vehicle clears in theory; in practice clearance margin too small; vehicle hits bridge. Posted height with margin. 9. No weight enforcement. Posted weight limits ignored; bridges damaged by over-load. Coordinate with RTO enforcement. 10. Design vehicle different from used vehicle class. Bridge designed for Class A; Class 70R used; over-stressed. Match design vehicle to expected traffic. 11. No vehicle damage factor (VDF) calibration. VDF assumed; actual vehicle mix different; pavement damage accelerated. Periodic VDF calibration via traffic studies. 12. No ODV permit system. Heavy / over-dimensional vehicles cross without notification; structural damage; cumulative effect. Coordinate ODV permits + bridge ratings. 13. Geometric design + vehicle envelope inconsistent. Approach radius for WB-12, but design vehicle list includes WB-21. Coordinate design vehicle envelope. 14. Pavement structural design inadequate for MAV growth. 10-year design but MAV proportion grows 5-10% per year; year-10 pavement under-designed. Sensitivity analysis. 15. No vehicle classification at toll plazas. Tolls collected without proper classification; revenue + damage tracking off. Modern OBU / FASTag systems.
Vehicle dimensions + weights — IRC 3 touchpoints:
1. Highway geometric design: - Design vehicle selection per traffic forecast - Off-tracking + sweep path analysis - Curve radius + extra widening per IRC:38:1988 - Intersection geometry per IRC:SP-21:2009
2. Pavement design: - VDF calibration per IRC:37:2018 - Axle load → ESAL conversion - Cumulative ESAL for design horizon
3. Bridge design: - Load class selection per IRC:6:2017 - Vehicle envelopes for geometric clearance - Vertical + horizontal clearance per IRC:7:2017
4. Traffic surveys + operations: - Classified vehicle counts - Truck distribution + ODV identification - VDF calibration via traffic studies
5. Regulatory enforcement: - Posted weight limits per Motor Vehicles Act - Posted height limits at bridges - Over-dimensional vehicle permits - Toll classification at toll plazas
6. Asset management: - Bridge load rating per IRC:SP-37:2010 considers current vehicle classes - Pavement performance prediction - Future-vehicle growth assumptions
7. Periodic updates: - Vehicle classifications evolve (electric, autonomous, etc.) - IRC 3 revisions every 5-10 years - Cross-reference codes need updating
IRC 3 is the foundational vehicle reference for all Indian highway + bridge + traffic design — invoked silently in every design calculation, every bridge load rating, every pavement structural analysis, every geometric design check.