Western Australian Current Regulations

ROAD TRAFFIC (VEHICLES) REGULATIONS 2014 - REG 164

164 .         Mass limits for heavy vehicle wheels and axles

        (1)         In this regulation —

        retractable axle means an axle with a means of adjustment enabling it to be raised or lowered relative to the other axles in the axle group so that the tyres on the axle do not touch the ground.

        (2)         For the purposes of this regulation, a retractable axle —

            (a)         must be taken to be an axle when it is in the lowered position; and

            (b)         must be taken not to be an axle when it is in the raised position.

        (3)         The mass on a wheel or axle of a heavy vehicle must not exceed the limit set by its manufacturer.

        (4)         The mass on an axle group or single axle of a heavy vehicle must not exceed the limit provided for it in the Table.

        (5)         The mass limit in the Table that applies to a heavy vehicle’s axle group that includes a retractable axle must be determined as if the axle did not exist, unless subregulation (6) applies.

        (6)         A retractable axle is part of an axle group for the purposes of the Table if, when the mass on the group exceeds —

            (a)         6 t, in the case of a tandem axle group; or

            (b)         11 t, in the case of a tri‑axle group,

                the tyres on the axle are in contact with the ground and the load‑sharing suspension system is operating on each axle (including the retractable axle) and tyre in the group.

        (7)         The sum of the mass on the axle groups and single axles of a heavy vehicle must not exceed —

            (a)         in the case of a complying bus without a trailer —

                  (i)         if the complying bus has 2 axles — 16.0 t; and

                  (ii)         if the complying bus has a rear tandem axle group fitted with single tyres on one axle and dual tyres on the other axle — 20.0 t; and

                  (iii)         if the complying bus has a rear tandem axle group fitted with dual tyres on both axles —22.5 t;

                and

            (b)         in the case of a combination consisting of a complying bus and a trailer — the sum of the mass limit specified for the bus in paragraph (a) and the mass limits of the axle groups and single axles of the trailer as provided in the Table; and

            (c)         in any other case — the sum of the mass limits of the axle groups and single axles as provided in the Table.

        (8)         Subregulation (7) does not apply to a heavy vehicle to which regulation 164A applies.

Table — Mass limits for single axles and axle groups

Description of single axle or axle group	Mass limit (t)
Single axles and single axle groups
Single steer axle on —
(a)         a complying bus	6.5
(b)         any other motor vehicle	6.0
Single axle or single axle group fitted with single tyres with section width of —
(a)         less than 375 mm	6.0
(b)         at least 375 mm but less than 450 mm	6.7
(c)         at least 450 mm	7.0
Single axle or single axle group fitted with dual tyres on —
(a)         a pig trailer	9.0
(b)         a complying bus or a bus licensed to carry standing passengers	10.0
(c)         any other vehicle	9.0
Twinsteer axle groups
Twinsteer axle group without a load‑sharing suspension system	10.0
Twinsteer axle group with a load‑sharing suspension system	11.0
Tandem axle groups
Tandem axle group fitted with single tyres with section width of —
(a)         less than 375 mm	11.0
(b)         at least 375 mm but less than 450 mm	13.3
(c)         at least 450 mm	14.0
Tandem axle group fitted with single tyres on one axle and dual tyres on the other axle on —
(a)         a complying bus	14.0
(b)         any other vehicle	13.0
Tandem axle group fitted with dual tyres on —
(a)         a pig trailer	16.5
(b)         any other vehicle	16.5
Tri‑axle groups
Tri‑axle group on a vehicle fitted with single tyres with section width of less than 375 mm on all axles, or single tyres on one or 2 axles and dual tyres on the other axle or axles	15.0
Tri‑axle group on a pig trailer with either single tyres with section width of at least 375 mm, dual tyres on all axles or a combination of those tyres	18.0
Tri‑axle group, on a vehicle other than a pig trailer, with either single tyres with section width of at least 375 mm, dual tyres or a combination of those tyres	20.0
Quad‑axle groups
Quad‑axle group fitted with single tyres with section width of less than 375 mm	15.0
Quad‑axle group fitted with single tyres with section width of at least 375 mm or dual tyres	20.0

        [Regulation 164 amended: SL 2025/20 r. 7.]