ISO 7656:1993

Overview

ISO 7656:1993 - "Commercial road vehicles - Dimensional codes" defines a standardized coding system for vehicle dimensions to support consistent vehicle data exchange and electronic processing. The standard establishes 132 dimension codes (including angles) for commercial road vehicles as defined in ISO 3833 and references the ISO three‑axis reference system and R‑point conventions from ISO 4130/4131.

Key topics and technical requirements

• Three‑element code structure: each dimension is identified by a code composed of:
  • Prefix "ISO" (to avoid confusion with other coding systems)
  • A type letter indicating dimension type: L (length), H (height), W (width), D (diameter), V (volume)
  • A number (see ranges below)
• Number ranges:
  • 1–99: internal dimensions (general)
  • 100–199: external dimensions (general)
  • 300–399 / 400–499: internal/external dimensions reserved for commercial vehicles
  • 500–599: cargo‑related dimensions
• Loading condition identifiers: codes may include loading condition markers such as K (complete vehicle kerb mass) and A (maximum authorized total mass) per ISO 1176.
• Measurement basis:
  • Dimensions refer to the ISO 4130 three‑dimensional reference system (X, Y, Z planes) and R‑point locations (driver seat reference) unless otherwise stated.
  • All measurements are parallel to the X, Y, Z planes unless specified.
• Examples of coded dimensions (representative, not exhaustive): vehicle height, approach/departure angle, ramp angle, ground clearance, overall length, axle wheel spaces, front/rear overhangs, track width, tyre outer width, frame width, seat heights, bunk clearance and seat track travel.

Applications

• Standardized interchange of vehicle specification data between manufacturers, suppliers, regulators, and fleet databases
• CAD and PLM integration where dimension codes map to model parameters
• Regulatory reporting and type‑approval documentation requiring unambiguous dimensional references
• Vehicle bodybuilder and upfitter design (ensuring fitted bodies respect clearances, overhangs, coupling heights)
• Telematics, spare parts and aftermarket systems that use standardized dimension fields for configuration

Who uses this standard

• OEM engineering and design teams
• Bodybuilders, upfitters and trailer manufacturers
• Regulatory authorities and testing laboratories
• Data providers, vehicle information platforms and telematics vendors
• Consultants and standards committees involved in vehicle data modeling

Related standards

• ISO 3833 (vehicle types and definitions)
• ISO 4130 / ISO 4131 (3‑D reference system, R‑point and passenger car dimensional codes)
• ISO 612, ISO 1176 and other referenced ISO road‑vehicle documents used for measurement definitions

Keywords: ISO 7656, dimensional codes, commercial road vehicles, vehicle dimensions, vehicle data exchange, ISO 3833, R‑point, vehicle design, electronic processing.