The European Commission (EC) has published the results of research into the effectiveness, costs and benefits of introducing Daytime Running Lights (DRL). This research suggested that a substantial number of casualties could be prevented if this was introduced across the EU. Further, it showed a positive benefit to cost ratio when the costs of fitting lamps and the environmental cost of running them was considered, (i.e. benefit/cost ratios >1). On the basis of this research the EC has now entered a consultation exercise on how best to implement DRL.In the past, a number of researchers have found flaws with some of the studies carried out into the effectiveness of DRL and some road safety groups are concerned that they could potentially have adverse affects for some road user groups, particularly for motorcyclists. For this reason, the DfT commissioned TRL to carry out a critical review of specific aspects of the research carried out for the EC in order to inform the DfT’s response to the EC consultation exercise. The work has involved TRL experts reviewing specific parts of the research reports produced for the EC, comparing the methods and findings with other related research and carrying out a sensitivity analysis on the cost benefit model used in the EC research.(A)
In order to reduce congestion on the motorway network, the Highways Agency (HA) aims to create additional road space without road widening by turning some hard shoulders into extra traffic lanes. This objective raises safety concerns associated with the parking of broken down vehicles that would need to be left on strengthened verges or towed to purpose built safe havens. In a parallel initiative, the HA aims to improve emergency access to, and egress from, the trunk road network through the provision of emergency turnaround areas in the road verge and other escape routes. The HA commissioned research into the possible use of grassed, cellular pavers to surface such areas on the road network, as they provide a less conspicuous refuge for unauthorised users. A range of pavers was reviewed and six systems were identified and tested for strength and fracture mode in laboratory tests. Design traffic was predicted and the maximum static load applied by propped trailers when disconnected from their tractors was determined. Pavement designs were formulated and two examples of concrete modular systems were built and tested in TRL’s pavement test facility. The pavements were trafficked by up to 50,000 standard axles with a rolling dual wheel and loaded statically by a 10 tonne load simulative of a propped axle of a trailer. Despite some deterioration of the pavers, the pavements remained serviceable suffering little deformation and thereby validated the designs as conservative. The research demonstrated that, providing appropriate engineering standards are developed, grassed, cellular systems should provide a viable surfacing for safe havens and for emergency access and egress routes. Road trials under typical environmental conditions are recommended to further develop paver and foundation specifications, pavement design and to select vegetation that can survive these difficult conditions without degrading the pavement’s functions. (A)
Congestion on Britain’s roads is an increasing problem and in recent years traffic volumes have increased to such an extent that parts of the network are often operating close to capacity. The Department for Transport (DfT) and the Highways Agency (HA) are committed to reducing traffic congestion by better management of the road network. The movement of Abnormal Indivisible Loads (AILs) through the network causes additional delays which could be reduced by a better understanding of how delays are related to the type of load and the conditions under which they are moved, and of the comparative monetary and environmental costs of road transport and other modes, particularly water. This has been approached through literature review, consultation of stakeholders, monitoring of AILs both live and via detector data, and development of a spreadsheet based model which calculates the queues, delays and costs caused by an AIL movement along its entire route, depending on the day and time of travel. This model, verified using MIDAS data, exploits a novel analysis of extended queues caused by moving bottlenecks. The value of modelling has been confirmed by the highly variable nature of AIL congestion costs, and the model is being used to inform decisions about the route and timing of some AILs. The study confirms the sensitivity of congestion costs to the number of lanes occupied, which should be kept to the minimum consistent with safety. Better information about operational costs and environmental impacts would also be beneficial.(A)
Previous TRL research had investigated the reasons for the change in trend for the number of car occupant deaths in the late 1990s. This report presents further research analysing data from the Co-operative Crash Injury Study (CCIS), one of Europe's largest car occupant injury causation studies. CCIS is now the most substantial source of information about seatbelt wearing in accidents in Great Britain. Seatbelt wearing rates were found to be lower among injured car occupants than in general traffic. The lowest rates were for the fatally injured: 80 per cent of male drivers killed during the day were wearing a belt, and 66 per cent at night. These rates did not change significantly between 1994 and 2004. A statistical investigation of CCIS data developed the understanding of what causes accidents to be least survivable in terms of collision parameters, detecting casualty patterns at differing levels of survivability and presenting trends in un-survivable accidents. CCIS data were analysed using the statistical programme 'AnswerTree', which applies the Chi-Squared Automatic Interaction Detector technique. It emerged clearly that CDC extent (a measure of deformation) and ETS (Equivalent Test Speed) are key to the survivability of an accident. High values of these variables lead to high un-survivability.
Congestion on Britain’s roads is an increasing problem and in recent years traffic volumes have increased to such an extent that parts of the network are often operating close to capacity. The Department for Transport (DfT) and the Highways Agency (HA) are committed to reducing traffic congestion by better management of the road network. The movement of Abnormal Indivisible Loads (AILs) through the network causes additional delays which could be reduced by a better understanding of how delays are related to the type of load and the conditions under which they are moved, and of the comparative monetary and environmental costs of road transport and other modes, particularly water. This has been approached through literature review, consultation of stakeholders, monitoring of AILs both live and via detector data, and development of a spreadsheet based model which calculates the queues, delays and costs caused by an AIL movement along its entire route, depending on the day and time of travel. This model, verified using MIDAS data, exploits a novel analysis of extended queues caused by moving bottlenecks. The value of modelling has been confirmed by the highly variable nature of AIL congestion costs, and the model is being used to inform decisions about the route and timing of some AILs. The study confirms the sensitivity of congestion costs to the number of lanes occupied, which should be kept to the minimum consistent with safety. Better information about operational costs and environmental impacts would also be beneficial.(A)
Concern has been expressed that current bicycle helmets may increase the risk of brain injuries from rotational motion. A range of child and youth bicycle helmets have therefore been tested to evaluate their linear and oblique impact performance. This data was used to assess the propensity of the helmet to influence rotational motion and was considered against post-mortem human surrogate data to allow comparison of the risk of injury to that of an unhelmeted head. Un-helmeted post-mortem human surrogate data indicates that a simple skull fracture for an unhelmeted head (injury rated as AIS 2) may occur at 5kN - 6kN which corresponds to between 100g and 150g for a head mass of between 4kg and 5kg. Assuming that the response of the unhelmeted head is similar to the helmeted head during an oblique impact at 8.5m/s at 15o, this may generate between 7500rad/s² and 12000rad/s² of rotational acceleration. This is potentially more severe than the 3000rad/s² to 8500rad/s² measured during abrasive and projection oblique tests with size 54cm (E) helmeted headforms. However, for the most severe cases using a size 57cm (J) headform, rotational acceleration was typically greater than 10,000rad/s² and increased to levels of 20,000rad/s², a level at which a 35% - 50% risk of serious AIS3+ injuries is anticipated. Overall, it was concluded that for the majority of cases considered, the helmet can provide life saving protection during typical linear impacts and, in addition, the typical level of rotational acceleration observed using a helmeted headform would generally be no more injurious than expected for a bare human head. However, in both low speed linear impacts and the most severe oblique cases, linear and rotational accelerations may increase to levels corresponding to injury severities as high as AIS 2 or 3, at which a marginal increase (up to 1 AIS interval) in injury outcome may be expected for a helmeted head. The true response of the bare human head to oblique, glancing blows is not known and these observations could not be concluded with certainty, but may be indicative of possible trends. A greater understanding is therefore needed to allow an accurate assessment of injury tolerance in oblique impacts. Linear impact performance, head inertia and helmet fit were identified as important contributory factors to the level of induced rotational motion and injury potential. The design of helmets to include a broad range of sizes was also concluded to be detrimental to helmet safety, in terms of both reduced linear and rotational impact performance. The introduction into EN1078 of an oblique impact test could ensure that helmets do not provide an excessive risk of rotational head injury. (A)
This report contains the results of a study to examine the contribution made to the shear capacity of reinforced concrete beams of shear reinforcement that does not comply with the detailing requirements of the UK bridge design code. The main goal was to determine whether it is possible to relax the detailing requirements and remove any unnecessary conservatism that might exist in BD 44. The report contains the results of a literature review as well as the conclusions of a testing programme to investigate different details. These details include wide or varying spacing of links, links with less than the nominal area, and links not surrounding the main tension steel. The report discusses areas where relaxations may be possible, drawing on the conclusions of the literature review, the test programme and the analysis. (A)
A High Occupancy Vehicle (HOV) or Car Share lane is a lane of the road designated for vehicles with two or more occupants. Car Share lanes are a potential method of encouraging greener travel by giving priority to vehicles with multiple occupants. The Highways Agency is currently investigating the feasibility of implementing such a lane on the M1 motorway. TRL were commissioned to evaluate the proposed design of the M1 HOV lane scheme using a driving simulator study. In particular, the project aimed to evaluate: the clarity of the signing and road markings; use and violations; impact on motorway exit behaviour and driver attitudes toward the scheme The simulator study was conducted with 47 participants. Participants were randomly designated as either HOV drivers or Single Occupancy Vehicle (SOV) drivers in order to examine the response of both types of users. The differences in behaviour between younger (17-44) and older (45+) drivers were also investigated. Results indicated that the majority of drivers were able to correctly negotiate the scheme. There were few violations by SOVs despite the frustrating circumstances where there was heavy traffic in the SOV lanes and virtually no traffic in the HOV lane. Results of the behaviour questionnaire indicate that there was some confusion over the rules governing the use of the car share lane under unusual circumstances (e.g. a lane closure); however, an effective publicity campaign has the potential to increase the efficiency with which drivers use a HOV lane scheme in the real world.(A)
Air quality monitoring in the London Borough of Brent has indicated that concentrations of nitrogen dioxide (NO2) and particulate matter (PM10) would exceed the respective objectives of the UK Air Quality Strategy. Therefore, the London Borough of Brent (LBB) commissioned TRL Limited to undertake detailed air quality assessments in three areas where air quality exceedences had previously been identified. These were Wembley town centre, Harlesden town centre and the ‘Ikea’ junction on the North Circular Road at Neasden. These detailed assessments were based upon local traffic activity data which were obtained during 2005. Specific measurements undertaken within each study area included local traffic speed, traffic flows and vehicle type. Further refinements included the estimation of vehicle age, vehicle fuel type and engine size. Baseline oxides of nitrogen (NOX), particulate matter with an aerodynamic diameter of less than 10mm (PM10), carbon monoxide, volatile organic compounds, methane and carbon dioxide emissions were estimated for the study areas for a 2005 baseline and the future years of 2007 and 2010. For 2007 and 2010 estimates were derived for two scenarios: ‘business as usual’ and for the introduction of a low emissions zone (LEZ). These detailed assessments showed that the establishment of an LEZ which included these three study areas would result in a reduction in PM10 emissions, and a slightly smaller reduction in NOX emissions, directly as a response to the introduction of cleaner vehicles into the vehicle fleet. The report concludes however that in 2007 and 2010, the LEZ option, in each of the study areas would have a marginal impact on reducing NO2 and or PM10 concentrations. The report considers both the emissions and air pollution modelling uncertainties and recommends how these might be addressed through refinements in those input data. (A)
in the context of footway and cycle track maintenance, with risk measured as the number of injury accidents per km walked or cycled. Detailed advice on risk management is given in relation to policy and categorisation, and on strategic, tactical and operational issues. From records of third party claims the probability of a person injuring themselves on a defect of given height is derived. The cost of these accidents and the number of accidents resulting in claims is also examined. Medical literature on aspects of walking, tripping and obstacle clearance is discussed as are the factors which influence whether a person fails to notice a defect, then trips or slips on that defect, then falls, and then injures themselves. A risk assessment model for footways is developed to calculate the number of accidents on a highway authority’s network. The model is based on deriving the probability that a person walking over a given defect will fall and be injured, and on the assumption that the numbers of defects on the network will be a dynamic balance between the rate at which they appear and the rate at which they are repaired. A software tool containing this model is under development. (A)
Renewable energy technologies are likely to become more important as other energy sources become depleted and the cost of power generation using fossil fuels rises. Renewable sources of energy have considerable potential for increasing security of supply and reducing CO2emissions although, in most cases, they require significant initial investment. This report describes a full scale trial to recover solar energy using photovoltaic noise barriers installed on the M27. In addition to the electrical performance of the system, whole life costs studies were undertaken to assess the benefits of a wider implementation of the technology. Any impact on driver behaviour due to the presence of a visible technology adjacent to the highway was also investigated, as were the implications on reflected noise levels of using a photovoltaic barrier as opposed to a conventional noise barrier. (A)
The European Directive on the Assessment and Management of Environmental Noise (END) has identified the importance of so-called ‘Quiet Areas’. The END requires Member States to produce action plans in order to protect these areas against any increase in noise in the future. In response, the Department for Environment, Food and Rural Affairs (Defra) has commissioned TRL to carry out a review of existing knowledge and to propose appropriate methodologies for identifying Quiet Areas. A review of relevant literature is presented together with a review of the END and relevant legislation/guidance to assist in the development of proposals for identifying Quiet Areas. Proposals for procedures to identify Quiet Areas in Agglomerations and Quiet Areas in Open Country are set out based on acoustic, land use and area criteria. In the longer term a more flexible approach which includes consultation with stakeholders and taking account of local opinion and perceptions. The more subjective approach recognises that noise exposure, land use and area criteria alone may not identify parks and open spaces which are most highly valued as Quiet Areas. (A)
Previous helmet impact research has indicated that current helmet performance, although beneficial, could be improved. TRL have demonstrated that improved helmet design has the potential to increase protection by more than 60% during both linear and oblique impacts and if all riders wore helmets with this level of safety performance, up to 100 lives a year could be saved in the UK (Mellor et al., 2007). The S0232/VF project (Motorcyclists’ Helmets and Visors- Test Methods and New Technologies) recommended a test protocol which specified a series of tests onto flat and kerb anvils at 6m/s and 9.5m/s in order to assess the performance of current helmets against the current state of the art of helmet design. This project involved subjecting five UN ECE 22.05 approved motorcycle helmet models to a series of linear and oblique dynamic impact tests specified by the Department for Transport (DfT). The objective was to ensure that the test and assessment protocols proposed as the basis of a consumer information programme are robust and suitable to allow their implementation. The protocols are based on the findings and recommendations made by the DfT project SO232/VF (Motorcyclists’ Helmets and Visors - Test Methods and New Technologies) and a collaborative European project (European Co-operation in the Field of Scientific and Technical Research, Action 327), known as COST 327. TRL was commissioned to complete a series of linear and oblique impacts at 6m/s, 8.5m/s and 9.5m/s and to provide technical comment on their appropriateness and suitability for implementation.(A)
Among the properties in the mandate for the harmonised European standards for both bitumen and asphalt are adhesion and durability. Both these properties are difficult to measure because the adhesion and durability of the bitumen is affected by the asphalt mixture in which it is used and vice versa. Therefore, an ad-hoc group was set up jointly by CEN TC227/WG1 and TC336/WG1 on adhesion and durability whose goal is to come up with a recommendation for test methods both to characterise bituminous binders with regards to binder adhesivity to aggregate and the durability of this adhesitivity after ageing/with time and to characterise the durability of adhesion and cohesion in hot bituminous mixtures. The Highways Agency funded a programme of laboratory tests to support the ad-hoc group that incorporated variants of the saturation ageing tensile stiffness (SATS) procedure in order to try to measure the durability of adhesion and cohesion in the asphalt mixtures. This report gives the findings of that programme together with the main conclusions that can be drawn from it. (A)
This report describes the available high-tech methods for the remote monitoring of highway structures for the purpose of providing information to assist in the management of these structures. Monitoring the performance of a structure, or one its component parts, during construction and in service, can provide vital information on the ability of the structure to maintain full serviceability throughout its design life and in many instances for much longer periods of time. In many cases, monitoring has helped to alleviate doubts about structural safety and serviceability, and has assisted in making decisions to keep structures in full or part service. Information on structural performance can also be used to develop improved design standards for future structures. The report focuses on the use of monitoring as a tool for the management of structures which have failed a strength assessment according to the requirements of BD 21 (DMRB 3.4.3). The report builds on the information contained in BD 79 (DMRB 3.4.18) which provides guidelines on the management of sub-standard bridges and the role that monitoring can play in order to keep these bridges in service. The report also considers the use of monitoring as a management tool for new and innovative structures. (A)
The recent innovation of using stress absorbing layers behind the abutments of an integral bridge may offer a means of reducing the seasonal build up of lateral pressures caused by thermal expansion of the deck. Following the decision to use this technique at Mount Pleasant Flyover, an opportunity arose to carry out an instrumented case history study to evaluate the performance of the stress absorbing layers. After earlier laboratory and pilot scale trials, a layer of polyethylene foam was placed behind one abutment and a layer of recycled rubber crumb sheet behind the other. Performance monitoring was carried out during the construction period and for just over three years in service. Measurements were taken of changes in deck length, strains and temperatures in the deck, lateral earth pressures acting on the abutments, changes in the thickness of the stress absorbing layers and settlement behind the abutments. The implications of the findings upon the design procedures for integral bridges are discussed. (A)
This report summarises the key findings of a research project on emissions of particulate matter (PM) from road vehicle non-exhaust sources, such as tyre wear, brake wear, road surface wear and the resuspension of road dust. The main aim of the project was to develop improved prediction methods for emissions and air pollution, primarily for use in the UK National Atmospheric Emissions Inventory, and using the existing literature and data. The project involved an initial literature review, the evaluation, development and application of emission and air pollution models, and a review of potential abatement options for non-exhaust PM. The findings and recommendations from each part of the work are presented in the report. One of the clearest messages from the project was that without new experimental data the emission factors for non-exhaust sources will remain highly uncertain. In order to improve the understanding, a number of general recommendations are provided. These include a review of tyre, brake and road surface materials in use, the chemical characterisation of the source materials, laboratory-based experiments to recreate the particle-generating processes, real-world measurements using instrumented vehicles, source apportionment studies for PM in ambient air, and the experimental assessment of abatement measures.(A)
Traffic emissions of non-exhaust particulate matter contribute significantly to the concentrations of PM10 and PM2.5 in urban areas. However, these emissions are not well quantified compared to, for example, the corresponding emissions emitted from vehicle tailpipes. This work uses non-exhaust particulate emissions estimated from new emission factors in air dispersion modelling studies of a number of roadside locations. The model predictions are compared with measured concentration data. The factors used to calculate the non-exhaust emissions modelled have been taken from two sources. The tyre, brake and road wear emissions factors are those given in the EMEP methodology documentation, and the resuspension emissions factors are derived both in an earlier report from project CPEA23/SPU82, and in the current report. Seventeen sites have been selected at which concentration measurements of PM10 were recorded for significant periods between 2000 and 2002; ten of these sites additionally have measurements of PM2.5. The majority of the sites are located in Greater London and two sites are in Birmingham, close to the University. For the London sites, detailed emissions calculations have been performed using activity data given in the London Atmospheric Emissions Inventory; less accurate source data were available for Birmingham. The air dispersion model ADMS-Urban has been used to model the calculated emissions and predict annual average particulate concentrations. The comparison between modelled PM10 concentrations and monitored data is good, with the model estimating on average a 6% higher concentration of the measured value. The comparisons between modelled and measured concentrations are less good for PM2.5, with the average modelled concentration being 26% greater than the monitored value. However, the latter results are influenced by the significant uncertainty surrounding the conversion factor from the measured TEOM values to their gravimetric equivalent; some discussion regarding this subject is presented in the report. The report also presents some results of idealised scenarios. These include calculations of the relative proportions of the various traffic emissions components from simplified major and minor roads. In addition, initial investigations are presented of how the different source characteristics of the non-exhaust emissions (for example, height above road surface) may influence concentrations, which in turn affects the derivation of the resuspension emission factors; this effect needs further study. Finally, some discussion is presented of recommendations for further work involving detailed source apportionment of modelled and measured concentration data at the level of the different chemical constituents of the particulates. (A)
While whole life costing is considered important, a literature review of the whole life costing of footways and cycle tracks found that there is little and contradictory guidance on which materials and methods result in whole life cost benefits. This report provides guidance on the whole life evaluation of footways and cycle tracks. The concept of whole life costing, its principles and a method of producing qualitative whole life costs are presented. Other aspects which affect the choice of footway materials and the wider costs, such as claims, accidents, regeneration schemes and sustainability are discussed. Whole life value is also considered; this aims to achieve the optimum balance between whole life costs on the one hand, and the aspirations, needs, and requirements of stakeholders on the other. Aesthetics can play a large role in choice of footway material in urban settings because aesthetically pleasing footways can encourage business and regeneration of an area. Information on construction and maintenance costs was obtained from a number of local authorities and showed that there were large regional variations in costs. Average costs and typical maintenance regimes were used to model the whole life cost of asphalt and flagged footways. It was found that in rural areas where maintenance is infrequent the whole life cost is dominated by construction costs and therefore flexible footways are the least expensive. In urban locations where there is a greater degree of vehicle overrun and disruption by utilities, maintenance is more frequent and the whole life costs of flexible surfacing and slabs are similar. However, slabs are thought more likely to cause trips, increasing accident costs. (A)
This report describes the work carried out to develop methods for the measurement of road edge condition for SCANNER (Surface Condition Assessment of the National NEtwork of Roads) surveys of the local road network. The objectives were to identify the relevant aspects of the edge condition of local road carriageways, to develop automatic techniques for measuring key aspects of edge condition and to provide workable specifications and assessment techniques so that methods may be implemented in surveys in 2007.The report includes an assessment of methods that make use of current SCANNER survey technology for determining edge condition and for assessing the condition of the road from the transverse profile shape. An edge condition indicator is proposed which combines the individual outputs of the different methods that assess edge condition. This was found to provide a good indication of the general level of edge condition at network level.The report examines enhanced methods for identifying edge deterioration, using high resolution transverse profile and colour image collection equipment not in routine use for SCANNER surveys. It was found that the targeted edge defects could be identified with variable degrees of success. An edge deterioration indicator based on the enhanced methods provided improved accuracy and more localised information regarding the edge condition, suitable for driving scheme level assessments. Recommendations are made regarding the adoption of the enhanced equipment and methods for future SCANNER surveys. (A)
