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

i

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.

1

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.

2

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.

3

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-

4

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.

5

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

6

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:

7

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

8

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

9

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

10

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.

11

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.

12

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.

13

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.

14

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.

15

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.

16

Figure 3: Rear impact configuration requirements

17

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.

18

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

19

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

20

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

21

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

22

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

23

A.3 Skeleton trailer

Figure 8: side view and top view of skeleton semi-trailer

24

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

25

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

26

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

27