draft tanzania standard medc9 (5037)p3 - …5037)p3-semi_trailers.pdf · medc9 (5037)p3 -...
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DRAFT TANZANIA STANDARD
MEDC9 (5037)P3 - Semitrailers for transportation of general cargo and freight containers
TABLE OF CONTENTS
0. FOREWORD ............................................................................................................................... i
1. SCOPE ........................................................................................................................................ 1
2. NORMATIVE REFERENCES .................................................................................................. 1
3. DEFINITIONS ............................................................................................................................ 1
4. SYMBOLS AND ABREVIATIONS ......................................................................................... 5
5. SEMI-TRAILER TYPES............................................................................................................ 6
5.1 According to construction ..................................................................................................... 6
5.2 According to application ....................................................................................................... 6
5.2.1 Container Carrier (Skeleton/Flatbed) ............................................................................. 6
5.2.2 Cargo (flatbed / low-bed, drop-bed & tippers) ............................................................... 6
6. GENERAL REQUIREMENTS .................................................................................................. 6
6.1. Axle loading ......................................................................................................................... 6
6.2 Dimensional requirements: ................................................................................................... 6
6.2.1 Overall Length: ............................................................................................................... 7
6.2.2 Overall Height ................................................................................................................ 7
6.2.3 Overall Width ................................................................................................................. 7
6.2.4 Rear overhang ................................................................................................................. 7
6.2.5 Angle of inclination ........................................................................................................ 7
6.2.6 Kingpin setback .............................................................................................................. 7
6.2.7 king pin height. ............................................................................................................... 7
6.3 Capacity ................................................................................................................................. 7
6.4 Ground clearance................................................................................................................... 7
7. SEMI-TRAILER STABILITY ................................................................................................... 9
7.1 Load distribution ................................................................................................................... 9
7.2 Center of gravity.................................................................................................................... 9
7.3 Dynamic loads ....................................................................................................................... 9
7.4 Axle location ......................................................................................................................... 9
8. MATERIAL USED FOR SEMI-TRAILER MANUFACTURER ............................................. 9
8.1 Metals for trailer .................................................................................................................... 9
8.1.1 Aluminum alloys ............................................................................................................ 9
8.1.2 Steel .............................................................................................................................. 10
8.1.3 Stainless steel ................................................................................................................ 10
9. SEMI-TRAILER COMPONENTS ........................................................................................... 10
9.1 Axles.................................................................................................................................... 10
9.2 Brakes .................................................................................................................................. 11
9.3 Electrical System ................................................................................................................. 11
9.4 Suspension ........................................................................................................................... 13
9.4.1 Mechanical suspensions ............................................................................................... 13
9.4.2 Air suspensions ............................................................................................................. 13
9.5 Kingpin ................................................................................................................................ 14
9.6 Landing Leg/gear ................................................................................................................ 14
9.7 Twist locks .......................................................................................................................... 14
9.8 Tires ..................................................................................................................................... 14
10. STRUCTURAL INTEGRITY ................................................................................................ 14
11. TRAILER ATTACHMENTS AND ACCESSORIES ........................................................... 14
11.1 Rear Impact Protection ...................................................................................................... 14
11.2 Side Protection .................................................................................................................. 15
11.3 Spare Wheel Carrier .......................................................................................................... 15
11.4 Trailer Accessories ............................................................................................................ 17
11.5 Mudguards ......................................................................................................................... 17
11.6 Mud flap ............................................................................................................................ 17
11.7 Side makers ....................................................................................................................... 17
11.8. Vehicle retro reflective marking ...................................................................................... 17
12. REGISTRATION ................................................................................................................... 17
13. ROAD WORTHINESS .......................................................................................................... 18
13.1 Initial ................................................................................................................................. 18
13.2 Periodic.............................................................................................................................. 18
14. VEHICLE IDENTIFICATION NUMBER ............................................................................ 18
15. APPROVAL REQUIREMENTS FOR MANUFACTURES ................................................. 18
16. LABELING............................................................................................................................. 18
17. D-VALUE CALCULATIONS ............................................................................................... 18
17.1 D-Value Calculations for semi-trailer ............................................................................... 18
17.2 D-Value Calculations for full trailer and towing vehicle .................................................. 19
18. TESTING AND INSPECTION .............................................................................................. 19
19 .SEMI-TRAILERS SERVICE ................................................................................................. 20
20. SEMI-TRAILER CONFIGURATION ................................................................................... 21
ANNEX A: SEMI-TRAILER TYPE ACCORDING TO CONSTRUCTION ............................ 22
ANNEX B: WEIGHT AND DIMENSION LIMITS OF VEHICLES ......................................... 25
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0. FOREWORD
Transportation is an important sector in the growth of national economy, the use of semi-trailer is
common in transportation of general cargo and freight containers.
The operation, handling and transportation of general cargo and freight container is to be
monitored by relevant government authority.
In preparation of this draft standard assistance was drawn from Zambia standard ZS 916:2015 –
Semi trailers specifications.
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1. SCOPE
This standard specifies the requirements for semi-trailers meant for transportation of freight
containers and general cargo capable of operating at speeds above 30 km/h. This standard does
not cover the requirements of special purpose transport tractor trailers constructed for the
transportation of goods of abnormal weight and dimensions, or agricultural trailers. Also trailers
for carrying petroleum products and other hazardous products are not covered in this standard.
2. REFERENCES
In the preparation of this draft Tanzania Standard reference was derived from the following
publications:
TZS 1056: 2008 - Firefighting – Portable fire extinguishers – Performance and
construction (ISO 7165: 1999)
TZS 617:1999 - Pneumatic tyres for trucks and buses – Specification
ISO 830:1981- Specification for freight containers
ISO 1726-3- Requirements for semi trailer contact area to fifth wheel
TZS 698: 2012- Code of practice for inspection and testing of vehicles for road worthiness.
3. DEFINITIONS
For the purposes of this standard the following definitions shall be applied
3.1 Freight container
Freight container article of transport equipment
a) Of a permanent character and accordingly strong enough to be suitable for repeated
use
b) Specially designed to facilitate the carriage of goods by one or more modes of
transport, without intermediate reloading;
c) Fitted with devices permitting its ready handling, particularly its transfer from one
mode of transport to another;
d) So designed as to be easy to fill and empty;
e) having an internal volume of 1 m3 (35,3ft3) or more
f) Note 1 to entry: The term “freight container” does not include vehicles or conventional
packing.
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3.2 General cargo: Are goods which are loaded and transported individually and not in
intermodal containers or bulk as grain and oil. General cargo are transported in barrel,
crates, drums and bags, boxes e.t.c
3.3 Automotive Trailers: A non-self propelled vehicle having at least two wheels which on
account of its design and technical features is used to transport goods and is intended to
be towed by a motor vehicle.
3.4 Semi-trailer: A trailer which is intended to be connected to a motor vehicle and which is
so constructed that a portion of it is superimposed on and a part of it‟s weight is borne
by the haulage tractor.
3.5 Superstructure: Any structure built above the truck or trailer bed. It can be container for
storing goods or a crane mounted on the truck, etc.
3.6 Undercarriage: Means all the components in a trailer or semi-trailer under the frame.
This includes axles, suspension, brakes, electrical, landing legs, kingpin, rims, tires and
turntable in the full-trailer.
3.7 Manufacturer: The party that manufactures, produces, assembles, alters, modifies,
adapts or converts a trailer and “manufacture” has a corresponding meaning.
3.8 Suspension: Attaching parts including springs for securing axle or axles to chassis frame
and providing shock absorption to the vehicle. Trailer suspension may be mechanical leaf
spring or air suspension.
3.9 Load-Dividing Dolly: Is coupled between a tractor and semi-trailer to reduce the load
imposed by the semi-trailer on the tractor. It is a truck trailer with one or more axles
equipped with a fifth wheel, draw bar, and other parts necessary for its use.
3.10 Trailer Converter Dolly: A truck trailer with one or more axles equipped with a fifth
wheel, a drawbar, and other parts necessary to convert a semi-trailer to a drawbar trailer.
3.11 Low Bed Trailer: Means a trailer with a flat loading platform but with a swan neck or a
wheel arch both at the front and at the rear end. The platform height may be lower than
the trailer tyre diameter.
3.12 Semi low-bed trailer: Means a trailer with a flat loading platform but with a swan neck
or with an arch at the front end. The height of the platform may be equal to or more than
the trailer tyre diameter.
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3.13 Drop-bed trailer: A drop-bed trailer is lower than the low-bed trailer and its bed height
is so low that a hump has to be made around the trailer axles to accommodate the tires (in
addition to the hump in the front).
3.14 Double drop frame trailer: Means a trailer where the platform between the wheels is
dropped as low as possible to facilitate loading from fitted outboard.
3.15 Single drop frame trailer: Means a trailer where the platform is dropped behind the
front wheels for loading either by means of a ramp or other suitable method. The rear
wheels are usually fitted outboard.
3.16 Flat bed trailer: means a trailer with a flat loading platform without any swan necks or
wheel arches.
3.17 Swan neck (goose neck): Means the raised portion of the trailer beyond the loading
platform generally used to accommodate its own wheels or wheels of the towing vehicle.
3.18 Wheel arch: Means the raised portion on the platform of a trailer provided to
accommodate the vertical travel of its own wheels.
3.19 Drawbar: Means strut or column like device temporarily attached between the rear of a
towing vehicle and the front of the vehicle being towed. Its purpose is to maintain the
interval or distance between the two.
3.20 Fifth Wheel Coupling: Means a device used to connect a tractor to a semi-trailer and to
permit articulation between the units. It is generally composed of a lower half, mounted
on the tractor, consisting of a trunnion, plate and latching mechanism, for connection
with a king pin mounted on the semi-trailer.
3.21 Towing capacity: Towing capacity of the tow bar is equal to the total weight of the
trailer(s) towed.
3.22 Trailer body: Means the structure or fixture especially provided to contain or support the
material or property to be transported from one place to other.
3.23 Group of axles: Means axles being part of a bogie. A two axle group is called a tandem
and a tri-axle group a tri-axle bogie. By convention, a solo axle is considered as a group
of one axle.
3.24 Wheelbase for semitrailer: Means the distance of the axis of the semi-trailer fifth wheel
king pin to the centerline of the non-steering bogie axles, if one or more of the non-
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steering bogie axles has an axle lift device, then the wheel base with lowered / lifted
axle(s), whichever is the longer, is taken into account.
3.25 Length of Trailer: Means the distance between two vertical planes perpendicular to the
longitudinal median plane of the trailer and touching the front and rear of the trailer
respectively Note: To determine the length with draw gear, the tow bar is assumed to be
located so that the axis of the tow bar eye or coupling head is vertical and lies within the
foremost vertical plane.
3.26 Length of Semi-Trailer: Means the distance between two vertical planes perpendicular
to the longitudinal median plane of the trailer and touching the front and rear of the trailer
respectively and the distance between kingpin axis and rear end of semi-trailer. The
second value being placed in parentheses.
3.27 Retractable Axle: Means an axle which can be raised / lowered by the axle lift device
3.28 Loadable Axle: Means an axle the load on which can be varied without the axle being
raised by using the axle-lift device.
3.29 Axle-lift device: Means a device permanently fitted to a vehicle for the purpose of
reducing or increasing the load on the axle(s), according to the loading conditions of the
vehicle, by raising the wheels clear off the ground / lowering to the ground, in order to
reduce wear on the tyres when the vehicle is not fully laden and / or to make starting
(moving off) on slippery ground easier for motor vehicles or vehicle combinations, by
increasing the load on the driving axle.
3.30 Special Purpose Vehicles (Trailers): Means a vehicle meant for carrying goods and
performing a special function, for which special body arrangements and / or equipment is
necessary.
3.31 Extendable trailers: A Semi trailer constructed with telescopic chassis to enable the
overall length and wheel base to be in increased as required
3.32 Trailer Axle: Non-driven axle. It is a beam running crosswise to and supporting chassis.
3.33 Tandem Bogie: Means two axle wheels spaced by more than 1300 mm up to 2440 mm
from each other with defined load sharing ratio.
3.34 Tridem Axle or Triple Axle: Means three wheel axle with each axle spaced from each
other.
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3.35 Tridem Bogie: Means three axle wheels spaced from each other with defined load
sharing ratio.
3.36 Twist Locks: Device to lock the container with the trailer or semi-trailer frame.
3.37 Landing Gear/Landing Legs: Retractable supports for semi-trailer to keep trailer level
when tractor is removed.
3.38 Public road: The definition applied is as defined in the Tanzania Roads Act No. 13 of
2007.
3.39 Maximum weight: The maximum mass of a trailer and its load as specified by the
manufacturer.
3.40 Tare Weight: Empty weight of trailer without payload and without prime mover.
3.41 Payload: Actual weight of useful cargo carried by vehicle. This will include
superstructure (container or any other) and product.
3.42 Gross Vehicle Weight (GVW): Total weight of fully equipped truck (or trailer) and
payload.
4. SYMBOLS AND ABREVIATIONS
ECE Economic commission of Europe
GVW Gross vehicle weight
ISO International Organization for Standardization
TZS Tanzania standards
SAE Society for automotive engineers
daN Decanewton
g Acceleration due to gravity
kN Kilonewton
m Metre
MPa Megapascal
m/s2
Metre per second square
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5. TYPES OF SEMI-TRAILER
5.1 According to construction
Types of semitrailer according to construction are (See annex A)
Flat bed semi-trailer
Low bed semi-trailer
Skeleton semitrailer
Tankers semitrailers (TZS1114-2014)
5.2 According to application
5.2.1 Container Carrier (Skeleton/Flatbed)
Container carrier can be a semi-trailer or a full-trailer. The 40 ft container carrier shall have 4
twist locks. The 40 ft container carrier may be constructed to accommodate two 20 ft containers
and in such a case it must have 8 twist locks. Alternatively, we can have a 20 ft container carrier
with 4 twist locks. The container carrier may be constructed in such a way that it can be used for
transporting general goods in that case it will have a full deck (flatbed) otherwise it will be a
skeleton trailer.
5.2.2 Cargo (flatbed / low-bed, drop-bed & tippers)
The full-trailer or semi-trailer meant for carrying general cargo can be in numerous
configurations. The trailer may be a flat deck type or a low bed type in which case it has
gooseneck at the front to accommodate the prime mover. The trailer may have sidewalls and may
have superstructure to cover it completely with tarpaulin. The manufacturer shall ensure that
the superstructure complies with all the guidelines in this standard and other regulations.
6. GENERAL REQUIREMENTS
6.1. Axle loading
The permissible load on the axles shall be as per the prescribed limits under the Tanzania road
load act as amended time to time, such that the maximum axle load shall be;
a) 8 tonnes in the case of single axle with single tyre on either end
b) 10 tonnes in the case of single axle with dual tyres on either end
c) 18 tonnes in the case of tandem bogie with dual tyres on either axle ends or super single
d) 24.0 tonnes in the case of tridem bogie with dual tyres on either axle ends or super single
6.2 Dimensional requirements:
The dimensional requirements for trailers shall be as follows:
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6.2.1 Overall Length:
The overall length of the tractor-trailer combination shall not exceed 17metres for tractor-trailer
combination. The overall length of truck and full trailer combination is 22 meters. The overall
length of a semi-trailer should not exceed 12.5metres
NOTE: The overall length is measured between the fronts of the tractor to the rear most part of
the trailer. This excludes any part(s) projecting in front or rear (eg. Towing hooks, bumpers, etc).
6.2.2 Overall Height:
The overall height of the laden trailer measured from the road surface on which the trailer rests
to the maximum point of projection shall not exceed 4.6 metres
6.2.3 Overall Width
The overall width of a tractor-trailer measured at right angles to the axis of the tractor-trailer
vehicle between perpendicular planes enclosing the extreme points, shall not exceed 2.6 meters.
6.2.4 Rear overhang
Maximum rear overhang of a trailer should be 60% of its trailer wheel base or 3.7 metres lesser
6.2.5 Angle of inclination.
The fifth wheel should allow a minimum of 7˚ rearward inclination of the semitrailer, a minimum
of 6˚ forwards inclination of the semitrailer and a minimum angle of inclination of 3˚ sideways of
the semi-trailer
6.2.6 Kingpin setback
The kingpin setback should not exceed a maximum radius of 2 metres.
6.2.7 king pin height.
The height of the kingpin should be less than the fifth wheel height of the prime mover or tractor
to provide slope to the trailer.
6.3 Capacity
The maximum pay-load of the goods that have to be transported or the maximum combination
weight of the vehicle shall be such that when the trailer is fully loaded, its mass does not exceed
the appropriate requirements of the Road Traffic Act of united republic of Tanzania
6.4 Ground clearance
The ground clearance of a trailer, measured from a horizontal road surface to any point on the
underside of the trailer except the tyres, wheels and wheel hubs must, under the conditions of
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Maximum Loaded Test Mass loading as specified in the relevant braking rule, be not less than,
for any point in the width of the trailer which is within one meter fore and after
any„Axle‟,100mm
6.5. Slope
The semi-trailer should have a slope of about 0.5 to 1 in unladen condition. This is an
approximate figure and may vary by application and from manufacturer to manufacturer. The
slope is achieved by the difference in height of kingpin and fifth wheel. The slope is require for
proper mounting of prime mover and semi-trailer
6.7 Clearances
The trailer manufacturer shall ensure that proper clearances are incorporated in the design for the
following:
6.7.1 Fitting radius
When the tractor is coupled with the trailer, following clearances should be maintained:
Figure 1: Minimum clearance between tractor and trailer
6.7.2 Vertical swing clearance
The tractor and trailer must be able to articulate at least ±7dwegress in a vertical plane without
interference
6.7.3 Kingpin height
The king pin height shall be less than the fifth wheel height of the prime mover. This is for
provision of slope in the semitrailer
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Note: Each trailer is designed to be pulled by a specific prime mover. In case the operator
changes the prime mover then it is the operator‟s responsibility to ensure compatibility between
the prime mover and the trailer
7. SEMI-TRAILER STABILITY
7.1 Load distribution
The trailer load should always be reasonably distributed from side to side. The load shall be
centered as much as possible.
The trailer should be loaded front to back with at least 10% of the trailer weight on the
hitch. With typical trailers, more weight on the hitch is better for stability
The load should be secured so as not to shift.
7.2 Center of gravity
The overall center of gravity of the semi-trailer shall be calculated and shall be less than 95% the
width of the outer edge of the tires, (example 95% of 2.5 meters is 2.165 meters from ground)
For dangerous cargo, such as petroleum, the center of gravity shall be less than 85% the width of
the outer edge of the tires.
7.3 Dynamic loads.
All loads carried by the trailers should be properly fasten to avoid dynamic loading of the trailer
and to in hence stability of the vehicle
7.4 Axle location.
The axle should be located behind the load center for trailer stability.
8. MATERIALS REQUIREMENTS FOR MANUFACTURING OF SEMI -TRAILERS
8.1 Metals for trailer
Trailers will be manufactured using aluminum alloys and steel
8.1.1 Aluminum alloys
Aluminum alloys shall of either of following grades
a) Grade 1100, 3003, 3004, 5052, 5083, 6063, 713.0 and 6111 or equivalent standard should
be used for sheet metal work.
b) Grade 2014, 2219, A356.0 and 520.0 or equivalent standard should be used for trailer
frame and chassis
c) Grade 2017, 2011, 2024 and 2017 or equivalent standard should be used for trailer
mechanical fasteners
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8.1.2 Steel
A minimum require steel properties for trailer chassis manufacturing are shown it the
below table
Table 1: Minimum steel properties for trailer chassis manufacturing
Mechanical properties Minimum required values
Yield stress (MPa) 235
Tensile strength (MPa) 360
Elongation minimum. Lo=5.65√So(%) 22
Impact resistance at 20˚C, J 27joules
A minimum require steel properties for manufacturing other parts of the trailer are shown
it the table below
Table 2: Minimum steel properties for manufacturing other parts of the trailer
Mechanical properties Minimum required values
Yield stress (MPa) 172
Tensile strength (MPa) 300
Elongation minimum. Lo=5.65√So(%) 20
Impact resistance at 20˚C, J 20joules
8.1.3 Stainless steel
Stainless steel alloys shall be of either of the following grades
a) Grade SAE30202 and SAE30301 or equivalent standards should be used in trailer bodies
building.
9. SEMI-TRAILER COMPONENTS
9.1 Axles
a) Newly built trailer should have new trailer axles. Axles should be minimum 9-ton loading
capacity.
b) A Semi-Trailer shall be supported towards the rear by an axle group or one axle. A semi-
trailer shall have a maximum group of three non-steering axles. If it has more than three
axles group other axle should be steering axle.
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c) All axles fitted on a semi-trailer should be of a known manufacturer and the manufacturer
brand mark should be marked on all axles.
d) Every Semi-trailer which is extendible or fitted with a sliding „Axle Group‟ shall be
constructed so that
positive locking devices are utilised
all locking device controls shall be in a lockable enclosure when mounted on
the chassis;
failure of the engagement of the locking device shall activate a visible and/or
audible warning device;
where the locking device is air-operated the supply shall be fitted with a
protection valve to prevent loss of air to the air brake supply in the event of
line fracture or failure; and
the movable assembly shall be fitted with substantial stops to prevent
disconnection from the vehicle in the event of failure of the locking device.
9.2 Brakes
The trailer shall have 2-line pneumatic braking system with
i. Palm or plug-in couplings
ii. Emergency valve (for applying brakes automatically in case leakage),
iii. Automatic slack adjusters
iv. Quick release valves.
a) All axles shall have brakes. The trailer shall have ABS brakes in case the prime mover
has ABS brakes. Trailer ABS brake indication should be provided in the prime mover
b) Trailers shall have mechanical parking brake at least on one axle.
9.3 Electrical System
The trailer shall have 24-volt electrical system. The electrical system shall have the following
equipment:
9.3.1 Minimum 7-pin connector with 7-core cable going all the way to water-sealed junction
box at the rear end.
9.3.2 Wiring covered in safety conduit and properly terminated so that no exposed lose wires
are visible.
9.3.3 Rear lights including turn, brake, and taillights.
9.3.4 Side lights, at least 3 nos. on each side in amber color.
9.3.5 Number plate light.
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9.3.6 Side and rear reflectors.
9.3.7 Rear fog lights shall be provided.
9.3.8 Reverse alarm shall be provided.
The wire color coding is shown in figure 1 below
Figure 2: Wiring diagram.
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9.4 Suspension
The trailer should have one of the two types of suspension which will allows axle load
distribution. The suspension should be new and should be meant for trailers.
9.4.1 Mechanical suspensions
The trailer shall have mechanical suspension of suitable carrying capacity as per trailer design.
The suspension shall have the following
9.4.1.1 At least one adjustable connection/tie-rod per axle that is required for axle‟s
alignment.
9.4.1.2 Leaf spring of suitable capacity on each axle
9.4.1.3 Equalizing/ Balancing beams of suitable capacity
9.4.1.4 Hanger brackets of suitable capacity well welded to lower flange of trailer chassis
beam.
9.4.1.5 Axle Clamping System
9.4.1.6 All bolts in mechanical suspensions should be tied up properly and with a required
torque as recommended by the trailer /suspension manufacturer.
9.4.2 Air suspensions
The trailer shall have air suspension of suitable carrying capacity as per trailer design. The
suspension shall have the following
9.4.2.1 Air Suspension Hanger Bracket of suitable capacity, that transfers All Sideway,
travelling and braking forces from the axle to the chassis
9.4.2.2 Trailing Arm (Spring) of suitable capacity on each axle .Connecting element between
vehicle and axle of which Absorbs all vertical vibrations and all braking torque forces.
9.4.2.3 Axle Clamping System
9.4.2.4 Air Bag /Air bellows of suitable carrying capacity. All one side air bellows must be
connected together and must be installed in such a way there is a clearance between air
bellow and tires of minimum 20mm when the semi-trailer is loaded. Air bellow should
be of a known manufacture and it should bear manufacturer brand.
9.4.2.5 Shock absorbers of suitable carrying capacity on each axle
9.4.2.6 Leveling Valve thats maintains riding height of the semi-trailers . this valve must fitted .
The levelling valve must be connected at the chassis and axle.
9.4.2.7 Separate enough air tank for braking system and air tank for trailer leveling.
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9.4.2.8 Overflow valve to protect the braking system of the trailer at any time in case of any air
leakage is the trailer air suspension system.
9.4.2.9 Should have well defined wheel alignment mechanism
All bolts in air suspensions should be tied up properly and with a required torque as
recommended by the manufacturer.
9.5 Kingpin
Semi-trailer shall have king pin of suitable size according ISO 4086:2001
The trailer manufacturer shall determine the size of kingpin based on D-value calculations as
explained in item 16.
For new semi-trailers the kingpin shall be new and of internationally reputed brand.
9.6 Landing Leg/gear
Semi-trailers shall have landing legs in the front. The landing legs should be of suitable carrying
capacity with gear mechanism to lift the loaded trailer when required.
Note it is not recommended to unhook the loaded semi-trailer from the truck fifth wheel.
9.7 Twist locks
Trailers that transport shipping containers shall have twist locks to secure the container to the
trailer. The twist locks may be lever type or screw type. The semi-trailer shall have well fixed
reinforced and secure container locks to the trailer structure as per ISO 1161:2016
9.8 Tires
A trailer shall be fitted with tyres that comply with TZS 617:1999.
A combination of steel belted and nylon tyres on the same side of an axle shall be avoided.
All tires fitted on a semi trailer axle should be of the same size.
10. STRUCTURAL INTEGRITY
The trailer manufacturer must ensure the structural integrity of the trailer. The trailer
manufacturer must have the engineering capability to analyze the loads and their effect on the
structure and design a structure based on the loads.
11. TRAILER ATTACHMENTS AND ACCESSORIES
11.1 Rear Impact Protection
It is also called the rear bumper. Its purpose is to reduce the number of deaths or serious injuries
occurring when light vehicles impact the rear of trailers. The configuration requirements of rear
guard are shown in figure 3.
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11.2 Side Protection
Its purpose is to reduce the number of deaths or serious injuries occurring when other road users
impact the side of trailers. The approximate configuration requirements of side protection are
shown in figure 4. The figure is a guide only as trailers have various constructions. While
constructing the side protection, the trailer manufacturer must ensure that minimum open space
is left on the sides of the trailer.
11.3 Spare Wheel Carrier
The trailer may have one or two spare wheel carriers. The spare wheel carrier(s) may be of winch
type or cage type and may be mounted under the deck or above the deck.
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Figure 3: Rear impact configuration requirements
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Figure 4: Side protection configuration guidelines
11.4 Trailer Accessories
The trailer should have the following:-
a) Hub nut spanner
b) Wheel nut spanner
c) Jack of sufficient capacity
d) Wheel chocks
e) Traffic cones (at least 2)
11.5 Mudguards
Mudguard shall be fitted to cover the top part of tires to prevent mud to be lift up to the trailer.
11.6 Mud flap
Trailers shall be be provided with mud flap to cover the full width of the tire. Also mud flap
should have a maximum height of 203.2mm to the ground.
11.7 Side makers
All trailers shall have side makers on the left and right side on the trailer which are at the same
position from the bottom of the trailer.
11.8. Vehicle retro reflective marking
Trailers should have chevron reflector according to TZS 1733
12. REGISTRATION
The trailer shall have a unique registration with responsible authority.
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13. ROAD WORTHINESS
13.1 Initial
Approved trailer manufacturer in the country shall issue a road worthiness certificate at the time
of delivery of the trailer.
13.2 Periodic
The operator shall obtain road worthiness certificate according to current regulations.
14. VEHICLE IDENTIFICATION NUMBER
Trailer shall be provided with identification plate number of according to TZS 300:2010
15. APPROVAL REQUIREMENTS FOR MANUFACTURES
The manufacturers shall be approved /licensed and /or certified by appropriate authority
16. LABELING
The manufacturer shall mention the following in a permanent and visible manner on the trailer:
16.1 The manufactures name , trade name or trade mark
16.2 Vehicle Identification number
16.3 Year of semi-trailer manufacture
16.4 GVW
16.5 Axle load capacity
16.6 Tare/empty weight
17. D-VALUE CALCULATIONS
17.1 D-Value Calculations for semi-trailer
The maximum forces which are applied to a kingpin can be calculated by means of the D-value
formula as follows:
Mk = maximum permissible total weight of tractor in tons.
Ma = maximum permissible total weight of semi-trailer in tons.
A = maximum permissible load on main plate in tons.
g = 9.81m/s2
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17.2 D-Value Calculations for full trailer and towing vehicle
The maximum forces which are applied to a towing coupling can be calculated by means of the
D-value formula as follows:
Mk = maximum permissible total weight of tractor in tons.
Ma = maximum permissible total weight of semi-trailer in tons.
g = 9.81m/s2
18. TESTING AND INSPECTION
Testing and inspection requirements
CRITERIA TEST REQUIREMENT STANDARD
Overall length Certificate at delivery
and annual inspection
Max.semitrailer =12.5m
Max semitrailer /tractor
combination=17m
Approved
manufacturer issue
certificate
Overall width Certificate and delivery Maximum 2.6m
Overall height Certificate and delivery Maximum 4.6m
Axles Certificate and delivery
and every year
OEM plate and visual
check
Approved
manufacturer issue
certificate
Alignment Certificate and delivery
and every year
Shall be adjusted within
±3mm tolerance
Approved
manufacturer or
approved workshop
to check and issue
certificate
Brake system
integrity
Certificate and delivery
and every year
Operation check and
visual check. Brake
system should be as per
this standard
Approved
manufacturer or
approved workshop
to check and issue
certificate
Payload capacity Certificate Manufacturer should able
to prove by calculation
and testing, if required
Approved
manufacturer to issue
certificate
Electrical system
Operation check .Lighting
arrangement should as per
standard
Approved
manufacturer to issue
certificate
Structural integrity Visual check for cracks Approved
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Certificate at delivery
and visual check every
year
and bends manufacturer to issue
certificate
Kingpin Visual check Approved
manufacturer to issue
certificate
Landing legs/gear OEM plate and visual
Rear impact Must fulfill requirements
laid out by this standard
Side protection Must fulfill requirement
Laid out by this standard
19 .SEMI-TRAILERS SERVICE/MAINTENANCE
Semi-trailer services and maintenance should be done according to manufacturer instructions
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20. SEMI-TRAILER CONFIGURATION
See figure below for trailer configuration
A Trailer length E Axle spacing
B Wheel base F Trailer height
C Rear overhang G Trailer width
D Axle spacing H,I Twist lock spacing
Figure 5: Semi-Trailer configuration
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ANNEX A: SEMI-TRAILER TYPE ACCORDING TO CONSTRUCTION
A.1 Flat bed
Figure 6: top view sketch and side view sketch of flatbed semi-trailer
A.2 Low bed semitrailer
Figure 7: sketch of low bed semitrailer showing side view
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A.3 Skeleton trailer
Figure 8: side view and top view of skeleton semi-trailer
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A.4 Tanker semi-trailer
Below is a sketch of front view tanker semitrailer (the tank shall be according to TZS1114:2015)
Figure 9: tanker semi-trailer
A.5 Tipper semi-trailer
Figure 10: A sketch of semi-trailer tipper
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ANNEX B: WEIGHT AND DIMENSION LIMITS OF VEHICLES.
B. Category of trailer & combination of trailer and tractor
B.1 Tractor semi trailer dimension
DIMENSION LIMIT
Overall Length Maximum 17m
Overall Width Maximum 2.6 m
Overall Height Maximum 4.6
Tractor
Wheelbase Maximum 6.2 m
Tandem axle spread Minimum 1.2 m/Maximum 1.85 m
Semi-trailer
Length Maximum 12.5
Wheelbase Minimum 6.25 m/Maximum 12.5 m
Kingpin setback Maximum 2.0 m radius
Effective rear overhang Maximum 35% of wheelbase7
Tandem axle spread Minimum 1.2 m/Maximum > 1.85 m
Tridem axle spread Minimum 2.4 m/Maximum 3.7 m
Triaxle axle spread Minimum 2.4 m/Maximum 4.8 m
Track width Minimum 2.5 m/Maximum 2.6 m
Interaxle Spacing
Single Axle to Single, Tandem, or Tridem Axle Minimum 3.0 m
Tandem Axle to Tandem Axle Minimum 5.0 m
Tandem Axle to Tridem Axle Minimum 5.5 m
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B.2 vehicle weight limits
Front axle diff axle rear axle
8000kg 18000kg 24000kg
The maximum axle weight limits and maximum gross vehicle weight limits set out in this
Section are for axles equipped with dual tires and super single tires, except for steering axles.
WEIGHT LIMIT
Axle Weight Limits:
Steering Axle/ front axle Maximum 8000 kg
Single Axle (dual tires) Maximum 10000 kg
Tandem Axle (dual tires/ super single ) Maximum 18000 kg
Tridem Axle (dual tires/ super single ) Maximum 24000 kg
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