Showing papers in "TRRL RESEARCH REPORT in 1986"

Perceptual abilities of accident involved drivers

Abstract: The report presents an analysis of the visual and perceptual abilities of 370 accident involved drivers in relation to their accident experience. The drivers were volunteers from a group who had been involved in road accidents investigated as part of an in-depth "at-the-scene" study conducted by TRRL. In addition to the results of tests of static and dynamic visual ability, performance tests in a driving simulator and other tests of particular aspects of cognitive performance, data were available for each road user on age, experience, sex, average distance travelled per year and self reported accident histories. The distributions of the various abilities are given in the report, as are the results of correlation and group comparison analyses. A predictive model of accident frequency as a function of age, exposure and some of the "higher order" test results is presented. Once age and exposure had been allowed for, no correlations between accidents and "simple" visual or performance tests could be detected. The implications of the accident model are discussed, and possible directions for future research suggested. (TRRL)

The prediction of saturation flows for road junctions controlled by traffic signals

Abstract: DESCRIBES A COMPREHENSIVE PROGRAM OF MEASUREMENT OF SATURATION FLOW AT TRAFFIC SIGNALS AND THE DEVELOPMENT OF PREDICTION FORMULAS WHICH UPDATE THOSE IN: TRAFFIC SIGNALS BY F.V. WEBSTER AND B.M COBBE -- LONDON : HMSO, 1966

Ground vibration caused by civil engineering works

Abstract: Investigations have been undertaken to improve techniques for the prediction and control of ground vibration caused by civil engineering construction works. Contemporary damage and nuisance criteria are reviewed and factors affecting the input and propagation of ground vibration are discussed. Field data from numerous sites in the UK are summarised to provide some guidance as to the relative importance of various sources (e.g., traffic, piling, tunnelling, blasting). A methodology for trial blasting is given with recommendations for the deployment and specification of the equipment. Data processing and presentation format is described and a "site specific" scaling method given which provides improved correlation between peak particle velocity and scaled distance. The use of peak particle velocity as a damage-hazard specifier is discussed in relation to other dynamic parameters which also effect damage to structures. Options regarding the distribution of vibration associated risks between employer and contractor are considered in the context of legal and contractual obligations. (TRRL)

Long term disability following road traffic accidents

Abstract: The extent to which individuals involved in road traffic accidents suffer long term disability has been inadequately researched. There is insufficent knowledge about the duration of any such disability, the effect on post-accident routine or the cost to the community. Furthermore little is known about the relationship, if any, between the duration or severity of disability and the severity or type of the initial injury. This report describes work which aimed to determine whether there is any correlation between injury severity and subsequent disability, whether such disability was a consequence of particular injuries and whether the effects of long term disability should be included when costing road accidents. It was concluded that up to 24 per cent of all patients who had been involved in a road traffic accident developed a disability which lasted at least six months. The commonly used Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS) were found to be of little value in predicting the development of a disability. Only 28 per cent of patients with a residual disability were admitted to hospital, so that the examination of in-patient data alone would be likely to underestimate significantly the number of disabilities resulting from road accidents. Those injuries associated with the highest incidence of long-term disability were soft tissue injuries to the cervical spine ('whiplash' injuries) and closed fractures of the lower limbs. Present methods of costing road accidents which take account principally of in-patient costs are likely to underestimate their true cost. Further work on injuries resulting in a high incidence of disability and into the cost of out-patient resources is suggested. (TRRL)

Interviews with elderly pedestrians involved in road accidents

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A study of the cost-effectiveness of grading unpaved roads in developing countries

Abstract: Costs are determined for the maintenance of unpaved roads using motor graders, t ractor/ towed graders and tractor/mechanical drags based on field work in Africa. The cost-effectiveness is highlighted of using tractor/ towed grader combinations for the maintenance of properly constructed roads which are not badly deteriorated. Typical values of maintenance equipment availability for developing countries are given and the effect that this has on the cost of maintenance is determined. A method is proposed for determining optimum grading frequencies for roads using computerised investment models and this has been included in a recommended management method for recurrent maintenance. A grading frequency chart is developed for use by maintenance engineers in developing countries who do not have access to computer methods.

Car control conversions for disabled drivers

Abstract: This report presents the findings of a review of control conversions which are used by disabled drivers in Europe. The information was collected by correspondence with organisations in the European community, Scandinavia, Spain and Switzerland, and also by visits in the UK and in eight other countries of Europe. The report describes the range of control equipment which is produced in the UK and elsewhere in Europe, together with the technical developments and research which are taking place. The regulations, licensing and approval processes applied to control conversions were also studied and compared for different countries. (TRRL)

Observations of motorcycle riders at junctions

Abstract: Observations were made of motorcycles, scooters and mopeds at five different types of junctions: crossroads, with and without traffic lights; t-junctions, with and without traffic lights; and roundabouts. A total of 651 riders were observed who were making either left or right turns or proceeding straight on at junctions. The riders observed were chosen at random and were probably not aware that they were being observed. A majority (75 per cent) of those observed made some errors. The most common faults, at all junction types, were associated with rear observation, signals and speeding. Riders often failed to look behind them or to make adequate signals to other road users. Speeding faults did not necessarily involve exceeding the speed limit but arose from riding too fast for the prevailing conditions. Seventy-eight per cent of riders of machines displaying l-plates made at least one serious or dangerous fault which would have resulted in test failure if committed during the Department of Transport l-test. Seventy per cent of riders with machines not displaying l-plates made at least one error of this severity. (TRRL)

Corrosion of reinforcement: an assessment of twelve concrete bridges after 50 years service

Abstract: This report evaluates the results from corrosion investigations on twelve 50 year old bridges on the A82 trunk road between Bridge of Orchy and Invergarry in Scotland. The bridges experience a harsh environment and have been treated with deicing salts since the mid 1960's. Superstructural elements were surveyed by a contractor for reinforcement corrosion using half-cell potential, electrical resistivity, carbonation, chloride and cover measurements. These tests were supplemented by petrographic examinations of thin sections from cores and by measurement of compressive strength, density, cement and sulphate content to assess the condition of the concrete. The investigations showed that the beams and soffits of the decks have suffered the most corrosion as a result of the synergistic action of carbonation and chlorides. Data from the top steel of the decks were more difficult to interpret.

Park and ride at tyne and wear metro stations--a summary report

Abstract: Substantial improvements in public transport provision have been achieved in Tyne and Wear through the investment in the metro. To encourage travellers to transfer from their cars to the metro system, Tyne and Wear county council built or improved car parks at a number of metro stations. This report describes the combined effect of that car parking provision and the metro in attracting park and ride trips. The number of cars parked by metro passengers has increased by six times compared with the number of cars parked by BR passengers previously, from about 200 to about 1,200. Overall, there has been a two-fold increase in parking levels around stations since metro opened, to about one third of the total capacity. Fares paid by passengers using park and ride generated approximately L0.8M per annum in fares revenue in 1984. While theoretical studies suggest that there should be a small reduction in peak traffic flows on some roads due directly to park and ride, there has been no actual significant reduction in traffic congestion. This is not surprising since between 1979 and 1984 there was a 14 per cent increase in car ownership. On one busy part of the metro systems, park and riders are contributing to capacity problems during the morning peak. These and other findings are discussed in the report. (TRRL)

A suggested method of reliability analysis for earth retaining structures

Abstract: A new method for determining beta, the reliability index, (and hence the probability of failure) of an earth retaining structure, has been evolved. The method employs a standard of mathematics no higher than that used in the deterministic evaluation of a factor of safety. Although the method has not been tested by any rigorous mathematic treatment it has been numerically checked by Monte Carlo simulations. Using the proposed method values of beta have been obtained for several design problems. These values have been found to be very close to values of beta obtained from Monte Carlo simulations of the problems (generally using not less than 10,000 iterations). Because of the simplicity of the method it is hoped that it will prove helpful to civil engineers interested in the idea of using probability theory to assist in their design work. (TRRL)

Competition between bus services: the results of a modelling exercise

Abstract: The competition between stage service bus operators which will be allowed by the 1985 Transport Act has been investigated by modelling competition between two (and sometimes three) bus operators along a single high-density route. The intention was to see what amount of service each company would be likely to operate and at what fare, and whether the competition would lead to a situation in which competing operators could co-exist or whether the operator with the lowest costs would be able to price his competitors off the road. The results showed that, whatever way the details of competition affected the costs, under most conditions a given route is likely to be operated by more than one company only if their costs are very similar: if one operator can reduce costs to less than 90 percent of the other then the cheaper one can drive his competitor out of business.

Repair of cracked reinforced concrete: assessment of injection methods

Abstract: 1

Winter air temperatures in relation to frost damage in roads

Abstract: Very cold winters sufficiently severe to cause widespread damage to road foundations occur infrequently in Great Britain. A design procedure for new roads has been adopted which minimises the danger of frost-damage to subgrades by ensuring that the materials used in the construction of the road are not susceptible to frost-heave. Consequently, frost-susceptible materials are banned from the top 450 mm of construction throughout Great Britain. This approach relies on the assumption that for design purposes road pavements may be regarded as being at equal risk to frost penetration. This report describes a study of meteorological records for various sites (from Cornwall to the Scottish highlands) during the period 1959-1981. The frequency and severity of cold spells were examined with regard to the risk of frost penetrating deeply into a road. The results show that the present assumption of equal frost-penetration risk is untenable. Consideration should be given to reducing the thickness of non-susceptible construction required at a given site (with consequent economic benefits) on the basis of an examination of the meteorological records for the locality. Some further investigation is needed, because, in addition to finding the frequency of cold spells, the way in which successive spells combine to influence frost penetration must be taken into account. (TRRL)

An evaluation of unburnt colliery shale as fill for reinforced earth structures

Abstract: The National Coal Board, in seeking further outlets for using unburnt colliery shale, have considered that it could be a suitable fill material for reinforced earth structures although the Department of Transport regards it as being unsuitable for this particular purpose. The report reviews the situation and identifies five areas of concern; these are the effects of (1) acidity, sulphates and chlorides (2) swelling (3) heating (4) variability and (5) construction in wet weather. It is concluded that unburnt colliery shale should remain on the list of materials that are unsuitable for use in reinforced earth structures and that shale and mudstone should also be regarded as unsuitable. Attention is drawn to some of the problems that can arise from the use of pyrite-bearing shale and mudstone in general road construction. (TRRL)

Road-rail competition for freight traffic in kenya

Abstract: A study was carried out in Kenya to examine the scope for transferring long-distance freight traffic from road to rail as a way of reducing consumption of diesel fuel by the transport sector. Both lorries and railway locomotives are powered by diesel oil, but rail is more fuel efficient. Information on long-distance traffic volumes, commodity flows and modal split was obtained from road and rail surveys of freight traffic passing into, out of and through Nairobi. A survey of consignors indicated the importance of travel time and cost in determining their choice of mode. For long-distance traffic, in general, rail offers a cheaper but slower service than road, its price advantage increasing with journey length. Modal split for competitive traffic was analysed in terms of haul length and travel cost by each mode. The results suggest that consignors place an average value on time of around 1.5 K per tonne per day, which is far higher than usually assumed in economic studies. It is concluded that fuel savings resulting from transferring goods from road to rail by normal market forces would be modest, the realistic maximum being a saving of only one or two percent of national consumption of diesel oil. (TRRL)

Effect of prices on petrol and diesel sales in kenya

Abstract: To assess the effectiveness of fuel pricing as a means of controlling fuel sales in Kenya, time series analyses were carried out to quantify the effect that changes in price have had on sales of petrol and light diesel fuel between 1972 and 1981. While sales of both products correlated well with time or GDP, it was found that a GDP-based model gave more consistent results and that price had only a small effect on sales. Short-term price elasticity appeared to be around -0.1 for petrol and close to zero for diesel. The difficulty of measuring long-term price elasticity is discussed. It is concluded that taxing fuel is an effective way of collecting revenue but an ineffective way of controlling fuel sales in the short term. (TRRL)

Concessionary fares and pensioners' travel patterns: an analysis based on the 1978/9 national travel survey

Abstract: Concessionary fares schemes enable pensioners to travel free or at a reduced rate on public transport in the majority of local authorities in the UK. This report uses data from the 1978/9 national travel survey to examine the distribution of pensioners with concessionary travel on public transport, and the effects of concessions upon travel patterns. Particular attention is paid to estimating the extent to which different types of concession generate additional bus journeys that would not have been made if pensioners had to pay the full fare. (TRRL)

Accessibility by public transport in tyne and wear

Abstract: The effects of the public transport changes in Tyne and Wear on accessibility have been investigated. The most noticeable change in public transport has been the introduction of the metro but substantial changes have been made also to the bus services in the county. Three types of accessibility are considered -access (of workers) to jobs, access (of firms) to employed residents and access (of locations) to people (acting as a proxy for access to customers for retail or service firms). The analyses show that, with the exception of a few areas, there has been a general increase in accessibility. The greatest increases (up to 100 per cent in places) have occurred in Gateshead and in parts of Newcastle. The changes are substantially greater than those produced by the land-use changes in the county between 1971 and 1981. (TRRL)

Substitution of bituminous roadbase for granular sub-base

Abstract: Trials were carried out to investigate the strength of subgrade needed to allow rolled asphalt and dense coated macadam roadbases to be laid satisfactorily without a subbase. Having established that a roadbase could be laid on a relatively weak foundation test pavements were constructed to enable the performance of conventional and full depth pavements to be compared through the measurement of stress, strain and pavement deflection under load. Stress, strain and deflection calculated from linear elastic theory were not in good agreement with the measured values but theory indicated the same sensitivity of stress and strain to changes of asphalt thickness and dynamic modulus. It was therefore concluded that theory could be used to produce tentative designs by comparison with conventional designs. However, extensive road trials would be necessary to confirm the suitability of these theoretical designs and examine the practical problems of trafficking weak subgrades and compacting the lower pavement layers under difficult site conditions in wet weather. (A)

An anchored earth retaining wall on the otley bypass: construction and early performance

Abstract: 1