Showing papers in "Highway Engineer in 1982"

The demand for public transport

Abstract: This paper contains the authors' introduction and conclusions from "The Demand for Public Transport. The Report of the International Collaborative Study on Factors Affecting Public Transport Patronage" (1980) (See TRIS 334447), together with discussion on the report at the conference. For the covering abstract of the conference see IRRD abstract no 261650. (TRRL)

Effect of the clay fraction on some mechanical properties of lime-soil mixtures

Abstract: Artificially prepared, lime-treated mixtures of sand-clay were studied in the laboratory. The experimental programme was arranged with two types of clay mineral (kaolinite and montmorillonite), three levels of clay content (10,30 and 50 per cent), four levels of lime content for the kaolinite soils (0,2,4,8 per cent) and five levels for the montmorillonite soils (0,2,4,8,12 per cent). Two periods of curing (seven and 28 days) were employed. Firstly the maximum dry density optimum moisture content relationships for the 27 different mixtures were determined using one compactive effort. Test specimens for these mixtures were then fabricated at their corresponding optimum compaction conditions. The effect of the type and content of the clay fraction on the specimens' compressive strength, Q, cohesion, C, angle of internal friction, phi, and elastic modulus, e, was determined. The results showed that regardless of the clay content in the soil, increases in the values of q, C, and e due to lime-treatment are significantly higher for the montmorillonite than for the kaolinite specimens. Generally the most significant increase in any of these parameters occurs at two per cent lime for the kaolinite specimens, while for the montmorillonite specimens these strength parameters tend to develop progressively with lime content up to about eight per cent or even beyond. The pattern of increase in the angle of internal friction due to lime treatment is comparable for the two types of soil. The most significant increase occurs mostly up to two per cent lime where it reaches about 10 degrees. Good correlations between unconfined compressive strength and both cohesion and elastic modulus were observed. Linear regression equations for the prediction of and e for lime-treated soils from known values of g were accordingly established. (Author/TRRL)

Sodium chloride as an additive in lime-soil stabilisation

Abstract: Kaolinitic and montmorrillonitic soils were prepared from commercial quality sand and clay in 10, 30 and 50 per cent clay contents. Lime was added in 2, 4 and 8 per cent by dry weight of soil. The effect on optimum moisture content, maximum dry density and unconfined compressive strength of adding 1, 2 and 3 per cent of sodium chloride during lime treatment was investigated. At 28 days strength gains due to sodium chloride were generally higher in lime-kaolinite than in lime-montmorillonite soils. These amounted to between 100 and 300 per cent increase in unconfined compressive strength over that of the untreated or lime-only treated soils for clay contents between 30 and 50 per cent of the total soil composition. For most soils the optimum salt content for a maximum strength gain appears to be approximately one per cent. (Author/TRRL)

Public transport in third world cities

Abstract: This paper presents a review of public transport operations in cities of the Third World. It is shown that although this is a growth industry in most of these cities, the supply of conventional public transport is inadequate and para-transit systems have developed to fill the void. Operating costs and revenues are examined and although most undertakings are shown not to be profitable, it is explained that little support is provided by either central or local government. The development of para-transit systems is reviewed and the roles that these systems play and the problems they create are examined. The transport problems of low income communities are also considered, including the provision of transport to the urban poor and expenditure on transport. (a) (TRRL)

20 years of roundabout construction in buckinghamshire

Abstract: The paper covers the author's experience over a period of time when the use of roundabouts became very popular as a means of traffic control at important junctions in Buckinghamshire. The importance of attention to detailed design is stressed if roundabouts, particularly those of the small and mini variety, are to operate safely. The need for adequate deflection to control traffic speed through the roundabout is also emphasised. Extensive analysis of injury accident records at different types of roundabouts has been undertaken and comparisons made. The paper also deals with constructional and lighting aspects and concludes with comments on some of the advantages/disadvantages of roundabouts as opposed to traffic signal control in the management of traffic on urban road networks. The paper makes a plea for the development of a hybrid type of signal/off side priority control which would combine the best features of roundabouts and signal management. (Author/TRRL)

Tyre walls in highway construction

Abstract: Scrap tyres are a disposal problem. They are strong, durable and freely available in large quantities. Tyres can be a substitute for expensive civil engineering construction materials. West Yorkshire MCC has developed and implemented a system using scrap tyres as face and anchor units for retaining walls. Savings of over 75 per cent of the cost of a conventional retaining wall have been obtained. Details of construction and cost are given for a particular structure which was built using this system on M62 near Bradford. Tyres can also be used in new embankments to increase the steepness of the side slopes. Savings of at least 10 per cent are possible by designing embankments reinforced with tyres so as to obtain varying gradient side-slopes that efficiently match ground conditions. Examples on good and poor ground are considered. (TRRL)

Recent developments in surface dressing

Abstract: The paper reviews developments in the technology of surface dressing and describes how the use of such technology can lead to both improved performance and value for money. A rational design approach to selecting the surface dressing specification is introduced. Important design parameters such as the average least dimension of chippings and existing road surface texture, which allow the engineer to design for his particular requirements rather than typical average conditions are discussed. Experience of new techniques including double dressings and "racked-in" chipping systems is quoted as the basis for advice when specifying these techniques. Developments in specifications need to be complemented by developments in other aspects of the technology, and the paper also discusses developments in plant, binders, aggregates and the management of surface dressing. (Author/TRRL)

The practical impact of reduced investment in highway maintenance

Abstract: The progressive reduction in recent years in funds available to UK highway authorities for highway maintenance and improvement has resulted in substantial shifts in policy and in organisational and working methods at works unit level. The first section of this paper, dealing with the public sector, is primarily concerned with the practical effect of reduced investment at this level. The effect of legislative and other events on the use of resources in addition to the real terms reduction in funds is briefly discussed with particular reference to the Local Government and Planning Act, 1980. A review of the fluctuation in government and local authority expenditure in the maintenance and minor improvements sector since the 1960s opens the second section and is compared with the history of the industry's activity over the same period. Particular emphasis is placed on steps which the industry has had to take in order partially to protect the return on its investment and hence its ability to respond to the requirements of society and the public sector when such demands are made. Both sections of the paper conclude with a discussion of the possible future trends and consequences which would result from continuing low investment in the highway system. (Author/TRRL)

The homologation system

Abstract: In order to control better the quality and effectiveness of materials used in roadmarkings, the French government instigated, 25 years ago, a product homologation system whereby only homologated (i.e. approved) materials may be used on French roads. This was done with a view to ensuring a higher standard of markings and thus an improved road safety tool. In this paper the author describes how a product is homologated and details the strenuous trials it must undergo before it may be used on the road network. (Author/TRRL)