ISO 10998:2008

Overview

ISO 10998:2008 - "Agricultural tractors - Requirements for steering" specifies performance and safety requirements for both normal and emergency steering modes of agricultural tractors. It applies to tractors with a maximum design speed (per ISO 3965) up to (60 ± 3) km/h and excludes steel‑tracked tractors with maximum speeds up to (15 ± 3) km/h. The standard defines terms, test methods and acceptance criteria to verify predictable steering response, durability and safe behaviour of steering systems, including those with complex electronic control.

Key Topics

The standard covers technical and test aspects across the steering system lifecycle:

• Terms & definitions: Clear definitions for steering equipment, steering control, steering transmission (control and energy transmission), steered wheels, energy supply, and steering parameters (steering angle, steering time, steering forces, reaction forces).
• Types of steering: Manual, power‑assisted, full‑power, auxiliary (rear) steering, multi‑wheel/all‑wheel, articulated, compound and skid steering; also autonomous and advanced driver assistance steering functions.
• Performance & safety requirements: Predictable response, steering response behaviour, steering time and steering ratio considerations.
• Forces & failure simulation: Actuating forces, reaction forces, simulation of failures (increased steering forces) and criteria for acceptable behaviour under degraded conditions.
• Energy & warnings: Requirements for energy supply/reserve, storage reservoirs, warnings and fallback modes for power‑assisted or full‑power systems.
• Maintenance & durability: Adjustment devices, care/maintenance provisions, strength and durability testing of components.
• Electronic control systems: Special requirements and normative Annex A addressing safety aspects of complex electronic tractor control and advanced driver assistance/autonomous functions.

Applications

ISO 10998:2008 is intended for practical use in:

• Tractor manufacturers (OEMs) - design and validation of steering systems to meet safety and performance expectations.
• Component suppliers - hydraulic, electric and mechanical steering component design and testing.
• Test laboratories & certification bodies - executing the test procedures and acceptance criteria specified in the standard.
• Regulators & fleet operators - assessing compliance, procurement specifications and safe operation practices.
• R&D and integration teams - developing autonomous or driver‑assist steering features while addressing safety, redundancy and failure modes.

Keywords: ISO 10998, agricultural tractors, steering requirements, steering systems, emergency steering, power‑assisted steering, steering safety, steering testing.

Related Standards

Normative references cited in ISO 10998:2008 include:

• ISO 3965 - Maximum speeds (method of determination)
• ISO 789‑11 - Steering capability test procedures
• ISO 7000 - Graphical symbols
• ISO 14982 - Electromagnetic compatibility for agricultural machinery
• ISO 19879 - Test methods for hydraulic tube connections

Use ISO 10998:2008 when specifying, testing or certifying steering systems to ensure consistent safety and performance across agricultural tractor designs.