What is Traffic Impact Assessment - TIA

What is Traffic Impact Assessment (TIA) ?

TIA is a study/tool/mechanism to evaluate the transportation and traffic impact of a proposed land development project. It identifies the need for any mitigation measures for a transportation system to reduce congestion, maintain and improve safety. It provide the authorities/planners/developers a framework in making critical land use and site planning decisions regarding traffic and transportation issues.

Requirement for Traffic Impact Assessment (TIA) ?

For any land development projects that is expected to generate 100 or more peak hour vehicles, or when a project might impact an already congested or high accident area, or when specific site access and safety issues are of concern.

Aim of Traffic Impact Assessment (TIA)

To minimize traffic congestion and all related ills, in order to achieve a sustainable development

Importance and Significance of Traffic Impact Assessment (TIA) ?

• Legislative: mandatory for most land development especially in urban areas
• Micro level transportation planning that warrant analysis to gauge the impact of future developments on the surrounding road networks
• Done at the earliest planning stages of a project would assists in preparation of a more responsive and cost-effective site plan.

Applications of traffic volume studies

Applications of traffic volume studies

• Planning, traffic operation and control of existing facilities and also for planning and designing new facilities,
• Classified volume is used for structural design of pavement, geometric design and computing road user capacity,
• Volume distribution is used in planning one-way street and regulatory measures,
• Turning movement is used in the design of intersection, signal timing etc
• Pedestrian volume used for planning pedestrian facilities, sidewalk, crosswalk
• Traffic pattern and trend are used as measure for facilities improvement and priority of projects.

Preparation of earthwork report and detail drawings

Preparation of earthwork report and detail drawings

• Earthwork layout plan – should include existing level, proposed level, orientation of the building, location of silt trap, location of wash trough, total cut & fill, temporary earth drain system, proposed slope, existing slope, etc.
• Cross section of earthwork- show the varies of existing & proposed platform level
• Silt trap design & detail - for temporary earth drain
• Wash trough detail – to wash dump truck tire before move in & out to make sure public road is always clean.
• Calculation of cut & fill – to show whether the project have to import earth or export earth, use Cross Section Method or Contour Method or Grid method to calculate cut & fill.
• Earthwork specification – requirements to be followed during construction
• Piling specification – requirements for piling machine to be used during piling work, i.e, hydraulic hammer, diesel hammer, injection pile, etc, usually to avoid noisy during piling. 

Classification of Pile based on Methods of Installation

Classification of Pile based on Methods of Installation

Classification of pile based on methods of installation can be described in several items which is ;

Driven Piles
a) Timber (round or square section)
b) Precast concrete (solid or hollow section)
c) Prestressed concrete (solid or hollow section)
d) Steel H-section, box and tube

Driven and cast-in-place piles
a) Withdrawable steel drive tube, end closed by concrete plug
b) Withdrawable steel drive tube, end closed by detachable point
c) Steel shells driven by withdrawable mandrel or drive tube
d) Precast concrete shells driven by withdrawable mandrel

Bored Piles
a) Continuous bored
b) Cable percussion drilling
c) Augered
d) Large diameter under-reamed
e) Types incorporating pre-cast concrete units
f) Drilled in tubes

Composite Piles

General Attributes of Safe Road

Road Design for Safety

The operation of roads involves the interaction of three key elements that are driver, vehicle and the environment.Physical shape of road depends very much on the attributes of the driver and the vehicle and their interaction in a dynamic sense. Designing safe and efficient road requires a basic understanding of certain human factors, vehicle characteristics and their interaction with the roads and its environment.

Human factors include;

• Vision
• Information needs
• Information processing

Vehicle characteristics such as ;

• Visibility (for the driver-eye height and blind spot)
• Braking characteristics
• Manoeuvrability
• Cornering

What is General Attributes of Safe Road ?

1. Standards of horizontal and vertical alignment which are appropriate to the environment,
2. Road cross-section with appropriate lane and shoulder provisions, catering for the various traffic volume,
3. Access control consistent with the function of the road in the overall road network,
4. Clearly visible and uncomplicated intersection with appropriate traffic control providing safe movement for all road user groups
5. Well thought out traffic signing with clear advice, positive warning, unambiguous directional information,
6. Adequate and consistent delineation of the roadway,
7. High standard of skid resistance pavement with good drainage,
8. Appropriate street lighting
9. Overall traffic management which properly considers the needs of all road users.

Pile Driving Equipment

Pile Driving Equipment

The main components of pile driving equipment essentially consist of :-

1. Pile frames
2. Piling winches
3. Hanging leaders
4. Hammer guides
5. Piling hammers
6. Helmet, driving cap, dolly & packing

Retaining Wall Design Consideration and Major Types of Retaining Walls

Retaining Wall Design Consideration

Basic function of retaining wall is to retain soil at a slope which is greater than it would naturally assume, usually at a vertical or near vertical position. Retaining walls have primary function of retaining soils at an angle in excess of the soil’s nature angle of repose.

Walls within the design height range are designed to provide the necessary resistance by either their own mass or by the principles of leverage. During design stage, engineer must consider several important point which is vital and need to take account for such as ;

1. Overturning of the wall shall not occur
2. Forward sliding shall not occur
3. Materials to be used should be suitable and subject to availability
4. The subsoil will not overloaded
5. Nature and characteristics of the subsoil to be observed and examined very well
6. Height of water table. The presence of water can create hydrostatic pressure, affect bearing capacity of the subsoil together with its shear strength, reduce the frictional resistance between the underside of the foundation
7. Type of wall to be construct.

Major Types of Retaining Walls 

a) Mass retaining walls

Sometimes called gravity walls and rely upon their own mass together with the friction on the underside of the base to overcome the tendency to slide or overturn. Generally only economic up to 1.8 m. Mass walls can be constructed of semi-engineering quality bricks bedded in a 1:3 cement mortar or of mass concrete. Natural stone is suitable for small walls up to 1m high but generally it is used as a facing material for walls over 1 m

b) Cantilever walls

Usually of reinforced concrete and work on the principle of leverage where the stem is designed as a cantilever fixed at the base and the base is designed as a cantilever fixed at the stem. Economic height range of 1.2 m to 6 m using pre-stressing techniques. Any durable facing material can be applied to the surface to improve appearance of the wall

c) Counterfort retaining walls

Can be constructed of reinforced or prestressed concrete.Suitable for over 4.5 m.Triangular beams placed at suitable centres behind the stem and above the base to enable the stem and base to act as slab spanning horizontally over or under the counterforts

d) Precast concrete retaining walls

Manufactured from high-grade pre cast concrete on the cantilever principle.Can be erected on a foundation as permanent retaining wall or be free standing to act as dividing wall between heaped materials which it can increase three times the storage volume for any given area. Other advantages which is reduction in time by eliminating curing period, cost of formwork, time to erect and dismantle the temporary forms. Lifting holes are provided which can be utilized for fixing if required

e) Precast concrete crib-retaining walls

Designed on the principle of mass retaining walls.A system of pre cast concrete or treated timber components comprising headers and stretchers which interlock to form a 3 dimensional framework or crib of pre cast concrete timber units within which soil is retained. Constructed with a face batter between 1:6 and 1:8. Subsoil drainage is not required since the open face provides adequate drainage.