ISO 20500-3:2026

International
Standard
ISO 20500-3
First edition
Mobile road construction
2026-02
machinery — Safety —
Part 3:
Specific requirements for soil-
stabilising machines and recycling
machines
Machines mobiles pour la construction de routes — Sécurité —
Partie 3: Prescriptions spécifiques pour engins de stabilisation de
sol et machines de recyclage
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety requirements and/or protective/risk reduction measures . 2
4.1 General .2
4.1.1 Context .2
4.1.2 Specific relation to ISO 20500-1 .2
4.2 Visibility .2
4.2.1 General .2
4.2.2 Visibility performance criteria .3
4.2.3 Visibility performance criteria for the RB .4
4.3 Operator's station .5
4.4 Stopping .5
4.5 Access system to operator's station and to maintenance points.5
4.6 Protection .5
4.6.1 General .5
4.6.2 Mixing equipment . .5
4.7 Signal devices and warning signs .6
4.8 Electro-magnetic compatibility (EMC) .7
4.9 Noise .7
4.10 Vibration .7
5 Verification of the safety requirements and/or protective/risk reduction measures . 7
6 Information for use — Operator's manual . 8
Annex A (normative) Noise test code for soil-stabilising machines and recycling machines . 9
Annex B (informative) Examples of soil-stabilising machines and recycling machines .15
Annex C (informative) List of significant hazards .18
Bibliography .21

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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This document was prepared by Technical Committee ISO/TC 195, Building construction machinery and
equipment.
A list of all parts in the ISO 20500 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document is a type-C standard as stated in ISO 12100.
This document is of relevance, in particular, for the following stakeholder groups representing the market
players with regard to machinery safety:
— machine manufacturers (small, medium and large enterprises);
— health and safety bodies (regulators, accident prevention organisations, market surveillance etc.).
Others can be affected by the level of machinery safety achieved with the means of the document by the
above-mentioned stakeholder groups:
— machine users/employers (small, medium and large enterprises);
— machine users/employees (e.g. trade unions, organizations for people with special needs);
— service providers, e. g. for maintenance (small, medium and large enterprises);
— consumers (in case of machinery intended for use by consumers).
The above-mentioned stakeholder groups have been given the possibility to participate at the drafting
process of this document.
The machinery concerned and the extent to which hazards, hazardous situations or hazardous events are
covered are indicated in the Scope of this document.
When requirements of this type-C standard are different from those which are stated in type-A or type-B
standards, the requirements of this type-C standard take precedence over the requirements of the other
standards for machines that have been designed and built according to the requirements of this type-C
standard.
v
International Standard ISO 20500-3:2026(en)
Mobile road construction machinery — Safety —
Part 3:
Specific requirements for soil-stabilising machines and
recycling machines
1 Scope
This document, together with ISO 20500-1:2026, deals with all significant hazards, hazardous situations
and events relevant to soil-stabilising machines and recycling machines when used as intended and under
the conditions of misuse which are reasonably foreseeable by the manufacturer (see Annex C) associated
with the whole lifetime of the machine as described in ISO 12100:2010, 5.4.
The requirements of this document are complementary to the common requirements formulated in
ISO 20500-1:2026. This document does not repeat the requirements of ISO 20500-1:2026 but supplements or
modifies the requirements for soil-stabilising machines and recycling machines.
Lightning as a significant and relevant hazard is not covered in this document.
This document is not applicable to soil-stabilising machines and recycling machines manufactured before
the date of its publication.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3744:2025, Acoustics — Determination of sound power levels of noise sources using sound pressure —
Engineering methods for an essentially free field over a reflecting plane
ISO 5006:2017, Earth-moving machinery — Operator's field of view — Test method and performance criteria
ISO 10263-4:2009, Earth-moving machinery — Operator enclosure environment — Part 4: Heating, ventilating
and air conditioning (HVAC) test method and performance
ISO 11201:2010, Acoustics — Noise emitted by machinery and equipment — Determination of emission sound
pressure levels at a work station and at other specified positions in an essentially free field over a reflecting
plane with negligible environmental corrections
ISO 12100:2010, Safety of machinery — General principles for design — Risk assessment and risk reduction
ISO 20500-1:2026, Mobile road construction machinery — Safety — Part 1: Common requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12100:2010, ISO 20500-1:2026 and
the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp

— IEC Electropedia: available at https:// www .electropedia .org/
3.1
soil-stabilising machine
machine, either self-propelled or towed, with the function of pulverizing, breaking-up, aerating,
homogenizing, and loosening existing and/or imported soil and optionally mixing them together with water
and/or binders, e.g. cement or lime
Note 1 to entry: Examples can be found in Figures B.1, B.2, B.4 and B.5.
Note 2 to entry: The main purpose of a soil-stabilising machine is to improve the mechanical and physical properties
of the soil material by mixing it with binders (cement, lime, etc.) or filler.
3.2
recycling machine
machine used for the rehabilitation of road structures using reclaimed materials, additionally mixed with
binders (e.g. bitumen or cement) and reapplied in situ
Note 1 to entry: Examples can be found in Figure B.3.
3.3
mixing equipment
power-driven tool carrier, equipped with tools for the mixing process, which rotates during the mixing
operation
3.4
mixing drum
power-driven tool carrier comprising a cylindrical body, equipped with tools for the mixing process, which
rotates during the mixing operation
Note 1 to entry: Examples can be found in Annex B.
4 Safety requirements and/or protective/risk reduction measures
4.1 General
4.1.1 Context
Soil-stabilising machines and recycling machines shall conform to the safety requirements and/or
protective/risk reduction measures of this clause. In addition, the machines shall be designed according to
the principles of ISO 12100:2010 for relevant but not significant hazards which are not dealt with by this
document.
4.1.2 Specific relation to ISO 20500-1
Soil-stabilising machines and recycling machines shall conform to the requirements of ISO 20500-1:2026, as
far as not modified or replaced by the requirements of this document.
4.2 Visibility
4.2.1 General
ISO 20500-1:2026, 4.2 applies with the following modifications.
ISO 20500-1:2026, 4.2.1, 4th paragraph does not apply.
Visual aids on soil-stabilising machines shall be located in the 180° arc centred in front of the operator with
the operator facing the front of the machine.

Soil-stabilising machines and recycling machines shall meet the following requirements:
— the visibility test shall follow the principles described in ISO 5006:2017;
— for ride-on machines with a standing operator, ISO 20500-1:2026, Annex G shall apply additionally.
4.2.2 Visibility performance criteria
The measurement result shall show no maskings, or maskings smaller than or equal to the performance
criteria with direct or indirect view as specified in Table 1, when tested using the setup details as shown in
Figure 1.
a) 12 m circle for soil-stabilising machines and recycling machines (e.g. operator's station position-
front)
b) RB (side view) for soil-stabilising machines and recycling machines

c) RB (top view) for soil-stabilising machines and recycling machines
Key
Y Y-axis and forward direction of machine
1 rectangular boundary, RB
H height of milling drum above ground in transport position (minimum 200 mm)
L distance from the machine to the RB (1 m)
NOTE 1 See Table 2 for the height of the RB.
NOTE 2 Origin of coordinate system in accordance with the specification of the manufacturer.
Figure 1 — Setup of machines
The distances for H shall be reported in the test report.
Table 1 — Visibility performance criteria
Sector A B C D E F RB
soil-stabilising machines and recycling machines
Eye spacing 205 mm 405 mm 405 mm 405 mm 405 mm 205 mm 405 mm
2 times
1 time 1 time
Number and 700 mm
2 times 1 time 1 time 700 mm 700 mm
a
width of and 300 mm
700 mm 1 300 mm 1 300 mm and 1 time and 1 time
masking 1 time
1 300 mm 1 300 mm
1 300 mm
a
The width of the masking in the RB is applicable to every masking occurring.
4.2.3 Visibility performance criteria for the RB
The measurement result shall show no maskings, or maskings smaller than or equal to the acceptable
maskings (300 mm) when evaluated using the eye spacing specified in Table 1 for the RB and using the test
object height for each region as specified in Table 2.
Table 2 — Vertical test object height by machine type and region of rectangular boundary
Machine Type Region of the RB
Front side Left hand side Right hand side Rear side
soil-stabilising ma- 1,5 m 1,5 m 1,5 m 1,5 m
chines and recycling
machines
4.3 Operator's station
ISO 20500-1:2026, 4.4 applies with the following addition:
— the operator’s station of soil-stabilising machines shall be provided with a cab to protect the operator
against dust (e.g. cement and/or lime) generated by the process, except where the intended use of the
soil-stabilising machine is exclusively the liquid binder application;
— the cab shall be equipped, so that an air conditioning system conforming with ISO 10263-4:2009 can be
fitted;
— consistent air inlet and distribution shall be provided at the cab;
— air inlet system shall be designed as to minimize turbulences and stirring of dust;
— the air inlet of the cab shall be equipped with dust filters.
NOTE 1 Filter classes and performance are dependent on the application’s dust classes. National regulations can
apply.
NOTE 2 Requirements for the dust classes and the determination of filter fractional efficiency can be found in e.g.
EN 1822-1:2019 and ISO 29463-2:2011, ISO 29463-3:2011, ISO 29463-4:2011, ISO 29463-5:2022.
NOTE 3 Recycling machines do not have to be equipped with a cab.
4.4 Stopping
ISO 20500-1:2026, 4.7.1 applies with the following addition:
It shall be possible to stop the mixing equipment, even while the power unit (engine) is running.
4.5 Access system to operator's station and to maintenance points
ISO 20500-1:2026, 4.9 applies with the following modifications:
— the height of the lowest step of access system to the operator's station shall be a maximum of 700 mm
above ground level;
— the lowest three steps (or less) may be mounted flexibly in the lateral direction. In this case, those steps
shall be mounted as a unit.
4.6 Protection
4.6.1 General
ISO 20500-1:2026, 4.10 applies with the additions specified in 4.6.2.
4.6.2 Mixing equipment
4.6.2.1 General
For preventing access to the mixing equipment and debris being ejected, mixing equipment shall include
front guards in accordance with ISO 20500-1:2026, 4.10.2, rear guards in accordance with 4.6.2.2, and side
guards in accordance with 4.6.2.3.
NOTE These guards can be movable or can be fully opened for maintenance.

4.6.2.2 Rear guards
Rear guards shall be designed so that:
a) when they are opened for maintenance, operating the mixing equipment is only possible manually or in
the maintenance mode;
b) they shall be fitted with a holding device in order to be secured while opened for maintenance;
c) distances between the ground level and the lower part of the guard shall not exceed 1,5 times the mixing
depth during operation and in order to complete material discharge or the lowering of the mixing drum
adjacent to an obstacle;
d) a distance guard shall be fitted on those soil-stabilising and recycling machines, where the mixing
equipment is located at the rear of the chassis, see Figure B.4.
Structural parts of the machines and/or conveyors may be considered as part of the distance.
4.6.2.3 Side guards
Power-operated side guards of the mixing drum guards, intended to be controlled during operation of the
machine, shall conform to the following design criteria:
— the controls shall not lock in any position except in neutral (hold-to-run control), see also ISO 20500-1:2026,
4.6.2.1;
— the controls shall be fitted out of danger areas and allowing the operator view to the side guards;
— if operator´s places are provided for ground personnel, a yellow flashing light shall be fitted adjacent to
the guards of the mixing equipment and shall be activated whenever the controls are operated;
— the power-operated side guards shall automatically return to their normal (pre-set) position when the
controls are released except when the milling drum is stopped;
— the side-guards shall be designed so that they can only be locked in the raised position (e.g. for
maintenance) when the milling drum is off or in maintenance mode;
— side-guards may be at intermediate mode keeping them lifted above the material but not exceeding the
permissible values of ISO 20500-1:2026, 4.10.
NOTE This intermediate mode is intended to circumvent obstacles, eject debris and inhibit side-guard sinking
into the material.
4.6.2.4 Maintenance
For maintenance and cleaning of the mixing equipment (e.g. replacing the mixing tools) it shall be possible
to turn the mixing equipment either manually (e.g. using a hand crank) or to turn the mixing drum in a
maintenance mode according to ISO 20500-1:2026, 4.10.2.4 with the following additions [see also 4.6.2.2,
a)]:
— The circumferential speed shall not exceed 0,25 m/s.
— The control shall be of the hold-to-run type.
— When the hold-to-run control is continuously actuated, the resulting motion should stop either within ¼
revolution, or within 4 s, whichever occurs first.
4.7 Signal devices and warning signs
ISO 20500-1: —, 4.15 applies with the following addition:

A legible and indelible warning sign (see e.g. ISO 9244:2008+Amd 1:2016, Figure C.22) shall be applied on
both sides to the guards of the milling equipment. They shall be visible from outside the danger areas.
4.8 Electro-magnetic compatibility (EMC)
ISO 20500-1:2026, 4.18 applies with the following addition:
The antenna shall be located successively on the left- and right-hand sides of the soil-stabilising machines or
recycling machines, with the antenna parallel to the plane of the longitudinal symmetry of the machine and
in line with the SIP (seat index point).
4.9 Noise
ISO 20500-1:2026, 4.19 applies with the following addition:
For the determination of the noise emission values, Annex A shall apply.
For soil-stabilising machines and recycling machines, the main sources of noise are the engine, the hydraulic
components, the cooling system and the working process (e.g. mixing process).
4.10 Vibration
ISO 20500-1:2026, 4.20 applies with the following addition:
NOTE Typical sources of vibration emission for soil-stabilising machine are e.g. driving on rough or uneven
terrain, the travelling s
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