Editorial

Editoria

Comparison of noise impacts from urban transport

When new transport schemes are considered, a key issue is the potential impact of noise. The reaction of people to noise however is both personal and subjective. Whereas all types of new urban transport scheme have noise evaluations, little work has been undertaken to date to compare the noise generated by the different modes of transport namely, a tram, car, bus and guided bus. The lack of such evaluations has implications for scheme perception when new modes are introduced, and such comparisons frequently form part of the public debate when systems are proposed. This paper outlines the assessment of noise and its measurement, reviews the limited published comparisons between modes and presents the results of an extensive series of noise measurements of in-service trams, buses and cars, (taken mainly within the Greater Nottingham area). The measurements have been made across a range of similar operational circumstances to allow comparison between the relative noise of particular modes. The paper concludes that from measurement across operational circumstances there should be little perceived difference in noise from buses and trams, but that proportionately cars can generate significant emissions

A performance approach to the design and specification of foundations for industrial ground bearing slabs and pavements

The foundations for industrial flooring and pavements are normally designed based on measurements, or prediction, of the California Bearing Ratio (CBR) of the subgrade, and from this the design thickness of the foundation is chosen utilising long established empirical relationships. The modulus of subgrade reaction (k) measured by static plate bearing tests may also be used, and is correlated to CBR. The thickness design charts are the same as those used for the design of highway foundations and are based primarily on observed performance. The foundations are then constructed to a recipe specification whereby specific (tightly graded) materials are placed and compacted upon the subgrade with specified plant. The soil CBR can only be regarded as an index property and does not directly or explicitly assess the primary functional performance parameters, of stiffness or strength. If CBR were replaced with direct measurement of these parameters, then the current empirical approach could be replaced with more powerful analytical design. Performance of the as-built foundation could then be better assured by compliance testing (end product) on site during construction. By moving to a performance-based specification approach, requiring some analytical foundation design, it is anticipated that more appropriate and efficient use of plant and materials can be made. This should enable better quality construction to be achieved, more efficient use of recycled materials or stabilisation of weak subgrades, hence leading to more sustainable construction. Recent research at Loughborough University has developed such a performance-based specification approach for the design of (major) highway foundations, and has assessed those devices suitable to measure the performance parameters for both design and compliance testing. In this paper the transfer of this technology to industrial flooring and paving is suggested. The benefits of a performance-based approach to foundation design and specification are explained. The loading and function of a foundation is described and the performance parameters required to perform these functions are detailed. Suitable methods currently available to measure these performance parameters are described in brief. Finally, the implications and benefits of a move to a performance-based specification approach are discussed

Implementation of a workplace parking levy: lessons from the UK

The UK government has made its funding contribution towards major local transport investment conditional on introducing some form of complementary innovative Transport Demand Management measures such as road user charging (RUC). It is intended that this will help constrain traffic and generate local funding contributions towards schemes. Nottingham a major UK City has consequently chosen to implement a workplace parking levy (WPL). This paper presents a case study of the project, outlining its development and explaining the public consultation process used and its findings. It presents a summary of the perceptions of the WPL scheme from the consultations undertaken. From this lessons can be learned which will aid other Cities contemplating such schemes. The findings reveal that a communication strategy is vital, that WPL is not perceived as the most equitable of systems by many stakeholders but can be considered as an easy and quick policy to implement where the transport funding needs outweigh the negative aspects. WPL could perhaps be considered as a precursor to full RUC as the costs and technological barriers to RUC are reduced. It is also shown that promoters need to produce complementary strategies in order to assist implementation of WPL at an early stage in scheme development. This includes measures for assistance with employer travel planning and parking restraint. Promoters must have a clear strategy as to where the funding created by WPL will be hypothecated and what the benefits will be both to WPL payers and the general population as a whole

An investigation into Atterberg limits and their suitability for assessing the shrinkage and swelling characteristics of clay soils for foundation design.

Clay soils shrink and swell with changes in moisture content. This can be exacerbated in the presence of trees, and in the vicinity of buildings, the resultant effects can cause structural damage. For foundation design in such circumstances in the UK, reference is often made to guidelines published by the National House Building Council (NHBC), which were primarily written for low-rise residential structures. These guidelines are based on a clay shrink / swell potential assessed using Atterberg Limits and a 'water demand' classification for trees. Atterberg limits are semi-empirical tests that assess a fraction of a soil sample which passes an arbitrary sieve size. The structural features of clay soils, mineralogy, chemistry, prior stress history and cyclic effects all influence the magnitude of volumetric change. Atterberg limits do not directly measure any of these features but have been related to some of them empirically. This paper reviews the processes of clay shrinkage and swelling and the applicability of the Atterberg limits in the assessment of volume change potential. It concludes that modifications to the NHBC guidelines can make designs more site specific. However, because the guidelines are based on a cost - benefit analysis, they will over-design foundations for structures other than low rise residential houses and will not be relevant for others. It is concluded that a more appropriate analysis should be based on a wider overall assessment of all the available soil/site information, in conjunction with a simple assessment of plasticity

A comparison of devices for measuring stiffness in situ.

The variability between devices that measure the stiffness of a road foundation in situ and their accuracy are important considerations for the introduction of such field assessment methods into the construction monitoring process. The aim of this paper is to present the significant findings of recent research into the comparability of four such stiffness devices. Results have been obtained from commercial construction sites and large-scale field trials covering a wide range of material type and stiffness. In addition, controlled tests on a synthetic rubber were carried out to investigate repeatability, as well as a study to investigate the stress dependency of the computed stiffness values. The results show significant variations in the correlation coefficients, which were shown to be dependent upon material type and construction methods. Conclusions are drawn with regard to the efficacy and accuracy of the four stiffness measuring devices and proposals made concerning their suitability for the range of site construction conditions and materials

Drainage behaviour of sport pitches - findings from a research study

The drainage design of sports pitches has traditionally been based on experience and can be considered an inexact science. Whilst the sport surface can be adequately drained to meet specific criteria, estimating outflows at the discharge point is more challenging. The hydraulic performance of sports pitches has not previously been measured in detail prior to this study. Within the wider industry and regulatory bodies there is a perceived contribution to local flood risk of the storm water and run off from sport pitches. It is also apparent that artificial pitches have in some cases been treated in planning consents as impermeable. Observations from industry have suggested that in reality the pitch drainage systems discharge low volumes of water and low peak flow rates, with limited surface runoff (especially from porous artificial pitches). However, in some cases, for artificial pitches in particular, at planning stage the drainage design has required to include off-line tanks to provide storm water storage and attenuation. A lack of technical guidance on sport pitch design and drainage benefits may be leading to overdesign, and prompted this study. This 3 year study comprised field measurements of weather and discharge behaviour at a range of artificial and natural turf pitches in England; laboratory physical model testing of pitch component hydraulic behaviour; and mathematical modelling to predict how a pitch system may be expected to perform hydraulically. Bespoke field monitoring apparatus was developed as part of the research to measure across a large range of flow rates and volumes. The experimental work in this study has provided the evidence to demonstrate that the porous pitch designs provide high attenuation of peak rainfall events and large capacity for water storage, similar to the requirements of SuDs based ‘source control’ designs required in new urban developments. The field monitoring observations suggest that in reality the drainage system behaviour is not as consistent or predictable as might be expected from assumptions made in design software and that in all cases the measured outflow water volume was far less than that estimated from rainfall as the total water volume flowing into the pitch drainage system. The experimental work, combined with the mathematical modelling, has highlighted the key mechanisms that provide resistance to flow and explain the attenuation behaviour observed. It is considered that in most cases insufficient head is created in the sub-surface layers to drive water to the lateral drainage pipes, and that the high frictional resistance to flow in the corrugated collector pipes provide large ‘head’ losses under the low hydraulic gradients. The research findings support the claims by many in the industry that in some cases planning approvals, where a lack of understanding or evidence on how pitches can attenuate and store water exists, may be causing the over-design of pitch drainage systems requiring unnecessary offline storage tanks

Briefing: sustainable drainage for sports pitch developments

Effective management of storm water is of paramount importance in urban development, and drainage design is usually governed by planning constraints. In the development of sports pitches, planning bodies often impose discharge constraints, and frequently class such areas as impermeable surfaces, thus treating their drainage behaviour in a similar fashion to roads and pavements, which may require the provision of separate attenuation. This briefing presents preliminary findings of a project to assess the drainage behaviour of sports pitch developments. The work undertaken to date suggests only a fraction of water falling on a pitch (rain) is discharged to the drains, identifying an apparent attenuation capacity and potential over-design within current sports pitch drainage systems. In addition to the low discharge volumes measured from pitch systems, there has also been a broad range of flow rates experienced. This led to the development of a bespoke flow monitoring device, FloPod. Designed and fabricated at Loughborough University, this device allows a broad range of flow rates to be measured without compromising aspects of data resolution and reliability – key factors that were not found in commercially available devices

Lightweight deflectometers for quality assurance in road construction

The use of Lightweight Deflectometers (termed LWDs in Europe, and occasionally PFWDs in the USA) for construction quality control or material investigation for road construction has increased worldwide. In the UK the change in pavement foundation design to a ‘performance based approach’ has brought about the use of Lightweight Deflectometers for field assessment of stiffness modulus. This paper reviews the LWD as a field evaluation tool. It discusses in some detail the test variables that can influence and affect the field data quality, and presents brief summaries of recent fieldwork where an LWD has been used as a quality control tool. The paper concludes both on the LWD usefulness and also its limitations for a variety of earthwork and road assessment scenarios, and describes a field test protocol for its use on a variety of materials. The findings demonstrate the flexibility of the LWD but also show that its determination of ‘stiffness modulus’ may differ from that of the conventional Falling Weight Deflectometer (FWD) to a varying extent. The paper provides a useful reference document for LWD users, consultants, material specifiers, contractors and clients

UK rail transport: a review of demand and supply

Over recent years the UK railway industry has seen unprecedented growth in the number of passengers and the amount of freight carried. Expansion in network capacity, however, has not kept pace with this growth. This has led to significant overcrowding and little or no capacity left to run more trains within existing stock or track provision. The UK government however has stated that as part of achieving ‘best value' it wants to further increase rail traffic, and has recently set out a strategy to optimise this. This paper reviews the issues associated with the growth in passengers, the demand placed on the network and the policy developed to accommodate and manage it. It identifies the capacity constraints and options identified for capacity enhancement. The paper concludes that while privatisation has made coherent decision-making difficult there is significant experience to be gained in the development of policy and route utilisation strategies