Table of Contents
TOC o “1-3” h z u Introduction PAGEREF _Toc514676433 h 21.Current Standards PAGEREF _Toc514676434 h 32.Criteria for Highway Development PAGEREF _Toc514676435 h 42.1.Function PAGEREF _Toc514676436 h 4?Purpose PAGEREF _Toc514676437 h 4?Safety PAGEREF _Toc514676438 h 5?Engineering PAGEREF _Toc514676439 h 52.2.Environmental PAGEREF _Toc514676440 h 6?Route Selection PAGEREF _Toc514676441 h 6?Design PAGEREF _Toc514676442 h 6?Economical PAGEREF _Toc514676443 h 72.3.Balance PAGEREF _Toc514676444 h 83.On Achieving the Balance PAGEREF _Toc514676445 h 9?Development of Scheme Options PAGEREF _Toc514676446 h 9
The aim of this technical report is to demonstrate the engineering, design and mathematics as directed in the Guidance Notes on the Application Process for Chartered Engineer; January 2016 and show the uplift of my academic knowledge gained through work experience and close the gap from a Bachelor of Science to a Masters Degree.
Over the past 19 years my career demonstrates continued progression from a Civil Engineering Highways Technician, working in Qatar as an Assistant Resident Engineer to my current role as a Highways Engineer. Over this time, I have studied part time obtaining both a Higher National Certificate (HNC) and Bachelor of Science Degree in Civil Engineering from Swansea Metropolitan University.
My technical report, will detail the design and construction challenges which I have comprehended while working as a Engineer both in the UK and Overseas.
Throughout my technical report I aim to show my technical knowhow expected of a Chartered Engineer as indicated in the Guidance Notes.
Current StandardsThe purpose of a road is to provide passage for people and goods from one location to another. It is a geometrical element through the landscape comprising of a series of straights and curves through both the horizontal and vertical planes. One of the primary aims of road design is to create an alignment, which through its geometric characteristics provides the end user with a safe environment. This is achieved with long established principles of design which take account of vehicle and driver characteristics, behaviour and road surface performance.
To obtain suitably designed road alignments, it is important to integrate horizontal and vertical elements together with cross sectional features and junction layouts. The aim is to create an experience by the end user of a free-flowing form without a visual break. Achieving this discontinuity within the road alignment is both visually pleasing and reduces the number of opposing messages transmitted to the driver.
Traditionally rural road alignments often follow ancient routes. Generally, these were not built to any kind of standard but have developed with gradual improvements to meet requirements over time. Land use and vegetation uses have adapted to these gradual changes, resulting in roads now an integral part of the landscape through which they pass. Nowadays, these are built to standards which have been developed using expected traffic volumes, modern vehicle developments and safety requirements.
The design standards within the UK is called the Design Manual for Roads and Bridges (DMRB). The DMRB comprises of a series of fourteen volumes of Standards, Advice Notes and other documents relating to designs, construction, assessment and maintenance of trunk roads including motorways. Roads which are designed and constructed using these standards tend to have a low accident rate compared to those built prior to the introduction of the standards.
TD 9/93 – Highway Link Design is the current UK national road design standard. This document is located within Volume 6; Section 1 of the DMRB and was introduced in 1981 with updates in 1993 and to the current version in 2002. Not only has it produced safe roads, it also provides designers with a considerable degree of flexibility, enabling designers to achieve more economic designs, while reducing the impact on the environment.
The guiding principles of the ‘Highway Link Design’ are that standards of curvature, visibility and other design parameters are based on Design Speed which relates to the anticipated speed of vehicles on the road. The Standard details how the varying elements relate to one another and ensure that the overall layout is acceptable in terms of safety, operation, economics and aesthetics.
Criteria for Highway Development.
A highway development requires consideration of three key criteria, within each of these criteria there are several detailed considerations;
FunctionPurposeLevel of Service – The level of service is a way to describe the general operation of the road. It is a quality measure describing the operational condition within traffic streams, generally in terms of service measures as speed and travel time, freedom to manoeuvre, traffic interruptions comfort and convenience. The term is closely related to capacity giving a quantitative measure of traffic. Service volume is the maximum number of vehicles, pedestrians, cyclists and other users which can be accommodated under permitted conditions at a given level of service.
Below is a list of the main factors that affect the level of service of a highway. Other factors such as lane widths, slope gradient, obstructions, traffic composition, population also influence maximum flows.
Speed and travel time;
Freedom to travel at desired speed;
Driver comfort and convenience;
Level of service is divided into six level ranges from A to F, these are described briefly below.
Level A – Represents a free-flowing condition where traffic flow is virtually zero. Only the geometric design features limit the speed of the traffic. Comfort and convenience levels are very high and traffic has freedom to carry out all manoeuvres.
Level B – Represents a reasonable free-flowing condition. Comfort and convenience levels are still relatively high and there is only a slight reduction of freedom and manoeuvrability. Where minor accidents do happen, these can be accommodated with minimal effect to traffic flow.
Level C – Represents a stable flow of traffic. Traffic flows are at a level where a small increase will restrict the ability to manoeuvre, especially when overtaking or changing lanes. Accidents can still be absorbed within the traffic, they will however result in minor traffic congestion starting to build up. Driver comfort will decrease considerably at this level.
Level D – Represents a highway operating at high levels but still stable. The slightest increase in traffic flows will result in significant operational difficulties.
Level E – This is the level where maximum capacity has been reached. Traffic conditions are unstable with any incident causing extensive queuing. Comfort is very poor and all speeds are relatively low.
Level F – Represents the highway of exceeding capacity. The operational conditions are highly unstable, traffic moving on a stop-go basis.
Design Targets – Minimal design targets for road alignments and cross sections are established to define a benchmark against preliminary sketched alignments. A realistic assessment of what is required is made at the beginning of the project, rather than to adopt a standard as the design develops. Design targets are a consequence of an examination of the different aspects of the project including road type; its place in the road hierarchy; the type and number of users, its future development potential and the standards of the adjoining networks.
Geometric Standards – All highways must be designed to the appropriate design standards as stated with in the DMRB. Where relaxations and departures from the relevant design standards are proposed, a thorough examination of all safety implications will be undertaken in accordance with TD9/93 – Highway Link Design guidance.
Junctions/Accesses – Within the DMRB Volume 6 Section 2, there are eight parts which relate to different junction and accesses. Each standard requires a complex approach to risk assessment as they are areas that are prone where driver error is a concern. When developing a junction or access consideration has to be given to road capacity, traffic volumes and geometry with an importance on safety issues being required.
Stopping Places –The location and design of each stopping place, integrated lay-by, picnic area and viewing point are essential when designing a safe facility for rest and relaxation for the driver.
Geotechnics – Geotechnical difficulties influence alignment selection and can add considerably to the construction cost. On smaller projects, difficult ground conditions may be a major constraint with regards to route selection, whereas on major projects an engineering solution to a geotechnical problem may be appropriate.
Earthwork Balance – A good design will aim to achieve a balance of material and minimise the import or export of construction material. This will limit off-site construction disturbance and influence the economic performance of the project.
Structures – Minimising the need for structures will dramatically reduce the cost of the project both during the construction and maintenance periods. Structures are generally required where the proposed alignment passes over a rail line, river or adjacent road.
Ease of Construction – Having a balance of both online and offline construction will influence the level of service for existing road users during the construction phase, particularly during the construction of the online section.
EnvironmentalRoute SelectionLandform Patterns – The scale, shape and appearance of fields, trees groups and other vegetation have a major effect on the different landscapes to which highway projects are built upon. New roads and road improvements can separate these patterns often resulting in visual change and potentially making management of the landscape difficult. By altering the landscape and landforms this effects the existing ground water and land drainage and will also lead to changes in the vegetation types. When developing in these areas, designers should take the opportunities to strengthen and improve these patterns and features making valuable contributions to the landscape.
Topography – Similarly to the landscape pattern, road geometry can influence the local topography, especially where the alignment requires areas of cut and fill and where embankments are held back with retaining structures becoming an integral part of the landscape.
Features – When building within the UK, you have to take consideration of the history of the land and whether the land that you are developing is part of a Heritage Site or Site of Special Scientific Interest (SSSI). The routing of a highway will take need to take these in to account and where possible physically avoid them or minimise any intrusion on the wider area. Similarly, considerations when designing should consider the effects the highway will have the local ecology and wildlife and quite often rerouting of wildlife trails are required.
People – Roads can influence peoples’ everyday lives. A new highway or change to an existing highway can change access and egress, increase noise, air quality or have a visual impact, all of which will need to be considered during the early design phase.
DesignDriver Awareness – Road geometry, carriageway surfacing, verges, boundary features and surrounding views including landscape features all effect the road user’s experience and its surroundings. With careful design and consideration, the design can exploit the surrounding landscapes and using retaining wall design and well-designed landscaping can screen any potential unattractive views. With well thought design and carful use of the surrounding landscape this will also influence the drivers speed and maintain a comfortably journey by the means of the road geometry provided.
Landscape Character – When developing any design, consideration must be given to the landscape character. This can also be referred to as beautification or artscape but can incorporate a varied array of features which will have a lasting effect on the overall design. Elements may include walls, fences, planting and street furniture, but can also include alleviation ponding or emergency flooding areas. Elements such as those mentioned will vary from design to design but will also vary throughout sections of a design to suit local circumstances.
EconomicalCapital Cost – These are the costs that are associated with one-off expenditure on the acquisition, construction or enhancement of significant fixed assets including land, buildings and equipment that will be used for more than one financial year.
It is more important to distinguish between capital and revenue account costs as there are significant accounting and taxations issues which stem directly from how a particular item of expenditure is treated. On a personal level, it can affect whether a particular transaction is subject to capital gains tax opposed to income tax. In a commercial environment similar issues arise, as well as the possible entitlement to capital allowances, and how such treatment effects profitable.
The capital cost of developments can include; Land or property acquisition; commissions; statutory fees; consultant fees directly associated with the development; materials, plant and equipment; labour; fixtures and fittings; project insurance; inflation; taxation and financing; internal costs directly associated with the development.
Operational costs incurred in day to day operations might include; Wages; utilities; Maintenance and repairs; rent; sales; general and administrative expenses.
Net Present Value (NPV) – NPV is the difference between present value of cash inflows and the present value of cash outflows over a period of time. NPV is used in capital budgeting to analyse the profitability of a projected investment or project.
Economic Development Opportunities – A benefit, profit, or value of something that must be given up to acquire or achieve something else. Since every resource (land, money, time, etc.) can be put to alternative uses, every action, choice, or decision has an associated opportunity cost.
Opportunity costs are fundamental costs in economics, and are used in computing cost benefit analysis of a project. Such costs, however, are not recorded in the account books but are recognized in decision making by computing the cash outlays and their resulting profit or loss.
It is crucial that when designing a project, each of the functions, environment, economic and function are of equal value or weight in the balancing process. There will be situations where there will be conflicting criteria, these areas should be resolved during to the design stage to achieve a balance.
On Achieving the BalanceOvertime, achieving a balance between function, economic and environmental has become difficult, especially with the increasing capacity required on the road network. Integrating roads within the surrounding networks is becoming more and more difficult especially with the sensitive route selection and design while meeting functionality, particularly without compromising on safety and without additional cost.
The use of flexibility within the DMRB Design Standards, including the TD9/93 ‘Highway Link Design’ becomes crucial where the landscape through which the road passes is particularly sensitive. The design aims to consider all factors to produce a route selection where the design strategy will either avoid or reduce the need for any mitigating measures. Through the design flexibility, problem solving and methodology offers maximum scope for the development of creative solutions to road design. With this in mind, the early involvement of the Design Team allows different disciplines to contribute to the project at the essential points of the design.
The design starts with the Project Brief. The brief must establish a clear and defined objective that sets out the realistic objectives of the project. Consultations between the Client and other third parties will be stated within the Project Brief the flexibilities within the design, functional requirements without constraining the Design Team.
Varying degree of scheme options are developed by the Design Team which as far as reasonably practicable meet the objectives stated within the Project Brief. These objectives are also used in the assessment of scheme options and the justifications for the selection of a proposed route.
Development of Scheme OptionsFor each project a series of broad improvements strategies should always be considered. This may involve the identifications of corridors separated by different routing strategies depending on the scale and nature of the project. The following range of options should be examined.
Traffic management, including traffic calming measures
On-line improvement options
Off-line improvement options
The Do Nothing option should be considered, not because it may achieve the scheme objectives but because it provides a useful baseline against Do Something options can be compared.
In certain situations, the scheme objectives may be achieved by adopting traffic nonengagement measures. Traffic management can also be utilised to solve specific problems identified within the Project Brief.
On-line improvements are those where most of the new proposed options lies within the corridor of the existing alignment. Scheme specific objectives will largely depend on whether an on-line improvement is a worthy consideration.
Off-line improvements while often will prove to be the best solution by means of achieving the effective design criteria, because of the environment constraints and associated cost with the development, off-line improvements can often be controversial, especially in the eyes of the public.
Depending on how close the preliminary sketch alignments, both on-line and off-line achieve the design targets, further attempts may be required to achieve an alignment which is satisfactory in geometric terms. During the preliminary stage I will produce a number of on-line options, off-line options and a combination of the two. Assessment of these options might prove that there is only one suitable option that matches all the criteria.