ISO 6549:2026

International
Standard
ISO 6549
Third edition
Road vehicles — Procedure for H-
2026-09
and R-point determination
Véhicules routiers — Procédure de détermination des points H et
R
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Description of the three-dimensional H-point machine . 3
5 Installation procedure for the three-dimensional H-point machine . 3
Bibliography . 9

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 39,
Ergonomics.
This third edition cancels and replaces the second edition (ISO 6549:1999), which has been technically
revised.
The main changes are as follows:
— editorial changes.
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
International Standard ISO 6549:2026(en)
Road vehicles — Procedure for H- and R-point determination
1 Scope
This document defines a three-dimensional H-point machine for use in the determination of the actual
H-point and torso angle of a seat, for the purpose of comparing these measurements to the manufacturer's
seating reference point and design torso angle. The three-dimensional H-point machine is intended to be
used as a checking device for one designated seat position at a time and is not a device which measures or
indicates an occupant's capabilities or comfort.
This document is applicable to any motor vehicle where:
a) the distance, vertically measured, between the operator heel point and the seating reference point is
less than 550 mm,
b) the torso angle is greater than 5° rearward of vertical or where the attitude of the thigh centreline as
indicated by the thigh bar is greater than 5° above the horizontal.
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 3833, Road vehicles — Types — Terms and definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3833 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
three-dimensional H-point machine
device used for the determination of the actual H-point (3.2.2) and actual torso angle (3.3.2) in a vehicle
3.2
H-point
pivot centre of the torso and thigh of the three-dimensional H-point machine (3.1) which simulates the pivot
centre of the human torso and thigh and is used for actual H-point (3.2.2) determination
Note 1 to entry: It is located on the centreplane of the device which is midway between the H-point sight buttons on
either side of the H-point machine.
3.2.1
seating reference point R-point
SgRP
design H-point
manufacturer's intended location for H-point (3.2), which is specifically designated as R-point or SgRP, and
which:
a) is the fundamental reference point used to establish occupant accommodation tools and dimensions;
b) simulates the position of the pivot centre of the human torso and thigh;
c) has coordinates established with respect to the designed vehicle structure;
d) establishes the rearmost normal design driving or riding H-point (3.2) location of each designated
seating position, which accounts for all modes of adjustment: horizontal, vertical and tilt that are
available for the seat, but does not include seat travel used for purposes other than normal driving and
riding
3.2.2
actual H-point
H-point (3.2) measured at the pivot centre of the torso line (3.3.1) and thigh bar centreline of the three-
dimensional H-point machine (3.1) using one of the appropriate leg lengths shown in Figure 1, with the seat
positioned at the seating reference point as specified by the manufacturer
3.3
torso angle
angle from vertical in side view of the lower flat portion of the torso pan of the H-point machine
3.3.1
torso line
centreline of the headroom probe in its fully rearward position against the torso pan of the three-dimensional
H-point machine (3.1)
Note 1 to entry: See Figure 2.
Note 2 to entry: The torso line intersects the H-point (3.2) and is parallel to the flat portion of the torso pan that
defines torso angle (3.3).
3.3.2
actual torso angle
angle measured between a true vertical line through the actual H-point (3.2.2) and the torso line (3.3.1) of
the three-dimensional H-point machine (3.1) installed in accordance with clause 5
Note 1 to entry: Torso angle is read from an indicator, called the hip angle quadrant, located just below the torso angle
(3.3) level on the H-point machine.
3.3.3
design torso angle
angle measured between a true vertical line through the seating reference point and the torso line (3.3.1)
Note 1 to entry: This angle is specified by the manufacturer.
3.4
centreplane of the occupant
C/LO
Y-coordinate of the R-point, in each designated seating position
Note 1 to entry: In vehicles with individual seats, the centreplane of the seat represents the centreplane of the
occupant. On bench seats, the centreplane of the occupant is specified by the manufacturer.
3.5
operator heel point
intersection of the right heel of the three-dimensional H-point machine (3.1) with the surface of the depressed
floor covering or other heel support, when the driver's seat is positioned at the seating reference point

3.6
foot angle
angle measured between the lower leg centreline and a line tangential to the bottom of the bare right foot
Note 1 to entry: A scale on the foot assembly of the three-dimensional H-point machine (3.1) indicates the foot angle. The
angle to the bottom of the device's shoe is 6,5° less than the bare foot angle because of the shoe sole and heel thickness.
4 Description of the three-dimensional H-point machine
The torso and seat pans of the three-dimensional H-point machine (see Figure 2) are representations of
1)
average torso and seat contours of an adult male.
Constructed of reinforced plastic and metal, these separate torso and seat pans simulate the human torso
and thigh and are mechanically hinged at the actual H-point to measure the actual torso angle. An adjustable-
length thigh bar, attached to the seat pan, establishes the thigh centreline and serves as a baseline for the
hip angle quadrant.
Lower leg segments, also adjustable in length, are connected to the seat pan assembly at the T-bar joining
the knees. The T-bar is a lateral extension of the adjustable thigh bar. Quadrants are incorporated in the
lower leg segments to measure knee angles. Shoe and foot assemblies are calibrated to measure the foot
angle. Positive stops are provided in the thigh and lower leg segments for the 50th and 95th percentile of
adult male dimensions (see Figure 1). Two spirit levels orient the device in space. Body element weights are
placed at the corresponding centres of gravity to provide seat penetration equivalent to a 76 kg male. All
2)
joints of the H-point machine shall be checked for free movement without encountering noticeable friction.
5 Installation procedure for the three-dimensional H-point machine
5.1 The vehicle shall be preconditioned at the manufacturer's discretion, at a temperature of (20 ± 10) °C
to ensure that the seat material reaches room temperature. If the seat to be checked has never been sat upon,
a 70 kg to 80 kg person or device shall sit on the seat to flex the cushion and back. At the manufacturer's
request, all seat assemblies shall remain unloaded for a minimum period of 30 min prior to installation of
the three-dimensional H-point machine.
5.2 Dimensions are measured relative to the vehicle three-dimensional reference system by setting up the
vehicle relative to the f
...