Overview
ISO 11407:2004 - "Commercial road vehicles - Mechanical coupling between towing vehicles, with coupling mounted forward and below, and centre-axle trailers - Interchangeability" specifies dimensional and interchangeability requirements for mechanical drawbar couplings used between towing vehicles (with the coupling mounted forward and below) and centre-axle trailers. The standard targets road trains carrying low‑density, high‑volume cargo and covers the geometry, classes and marking needed to ensure safe, interchangeable coupling across manufacturers and operators.
Key topics and requirements
- Interchangeability dimensions - Defines the key parameter A (distance between drawbar coupling axis and rear end of towing vehicle) in class values: 1 400 mm, 1 600 mm, 1 900 mm (low/high classes).
- Turning front (C) - Minimum front clearance C is calculated from vehicle width (W), A and a minimum safety clearance S. Practical form:
- C_min = sqrt(A^2 + (W/2)^2) + S
- Recommended minimum S = 250 mm (365 mm gives additional margin).
- Coupling heights and drawbar contour - Specifies coupling and towing‑eye heights for laden vehicles and drawbar geometry. Notes that drawbar‑eye dimensions reference ISO 1102, though centre‑axle trailers may need reinforced eyes.
- Rear end configurations - Distinguishes high and low rear‑end classes (low for vehicles fitted with tail lifts or extra equipment). Figures define permissible contours and clearances.
- Angles and articulation - Requires no contact for inclination α up to 6°; articulation angle β up to 90° must be permitted under manoeuvring.
- Marking - Vehicles and trailers should carry a permanent 150 × 150 mm plate indicating class/dimension A to ensure easy recognition and correct matching.
- Scope limits - Not applicable to dedicated/special combinations (e.g., extensible drawbars), nor does it set gross mass or overall dimension limits (these are legislative).
Applications and users
- Who uses it:
- Vehicle and trailer manufacturers, chassis and drawbar designers
- Fleet operators and logistics companies specifying interchangeable road train equipment
- Type‑approval bodies, procurement teams and test laboratories
- Practical uses:
- Designing centre‑axle trailers and towing vehicles to be interoperable across fleets
- Specifying coupling geometry to avoid interference with tail lifts and overhang equipment
- Ensuring safe clearance and articulation for mixed combinations and multi‑trailer road trains
Related standards
- ISO 1102 - 50 mm drawbar eye interchangeability (referenced for drawbar‑eye dimensions)
- ISO 11406 - Mechanical coupling for rear‑mounted couplings and drawbar trailers (different coupling location)
Keywords: ISO 11407:2004, commercial road vehicles, mechanical coupling, centre‑axle trailers, drawbar coupling, interchangeability, drawbar eye, road train.