1,720,983 research outputs found
Influence of lighting on road safety on motorways
No full textContributing towards safety is a primary objective of modern and efficient planning, in accordance with the Directives from the European Union and national legislation. Nowadays, guaranteeing a suitable safety level is the main aim to be pursued by the road engineer and manager of the road infrastructure.
The research verifies the impact of lighting on road safety and its effectiveness in reducing the number and gravity of accidents: in particular, attention is focused on the lighting of the principal Italian motorways.
A descriptive comparison has been done between the macroscopic variables observed in the presence or absence of artificial lighting. A qualitative estimate has been made of how much the lighting contributes towards traffic safety on motorways. It has been verified that artificial lighting makes a decisive contribution, reducing the number and seriousness of night-time accidents by around 30
The accident rate in urban area intersections: the use of neural artificial net to improve the road safety
No full textThe paper presents a research which tackles two issues. The first involves the study of different types of survey reports with reference to road accidents in urban areas: the aim is the identification of characteristics to make the survey reports more functional.
The second one consists of defining the functional relationship between some variables which the hazard level of an intersection depends upon. Particularly, accident data are used to check, with a neural artificial net model, what type of dependence links the accident rate in urban areas to the traffic flows, the geometric features of the intersection and the environmental characteristics (road paving, weather conditions...).
The pursued objectives contemplate a safety increase in the flow of traffic at urban intersections. An improved survey report layout implies a higher level of reliability of the data processing, and the use of neural nets allows a fast identification of the most suitable technical solutions to improve the safety of the intersections
Cold-mix asphalt for road foundations: use of cement and foamed bitumen in "high performance" pavements
No full textThe reduced availability of traditional aggregate, increasing environmental sensitivity and the high intrinsic value of marginal materials from the milling of the old damaged road pavements, have in recent years justified growing interest in “cold recycling” as a technique which can be used in the construction or rehabilitation of pavements, in spite of the use of “poor” materials. Cold recycling can be developed by means of cement and foamed bitumen. The technique gathers the benefits of the cold in situ recycling and those related to the use of the foamed bitumen. Despite its undisputed advantages, the above-mentioned technique has not yet been supported by a consolidated experimentation in Italy that attests to which factors could mainly affect the performances of the foamed mixture.
The paper describes an investigation aimed at testing foamed mixtures to be used in major roads. In particular, the influence of moisture, temperature and fine content on the mechanical performances of the material have been checked. The results demonstrate that pavements with cement and foamed bitumen foundations can be compared – in terms of bearing capacity and durability – with flexible pavements, on the basis of the Italian Design Pavement Catalogue
Mechanical characterisation of hydraulically bound mixtures for road foundations made with waste foundry sand and C&D aggregate
No full textThe paper describes a study of hydraulically bound mixtures, composed of foundry sands and C&D aggregate, produced for use in the foundation of road pavements. The investigations involved a physical and mechanical characterisation of the individual components, followed by that of the mixtures (by means of tensile strength, compressive strength, elastic modulus etc.). The results of the tests have been compared with the requisites for acceptance of traditional hydraulic mixtures in the main italian Contract Specifications, which has demonstrated that the analysed material is suitable for use
Acquisizione, elaborazione ed analisi spaziale di immagini per la gestione del degrado delle pavimentazioni stradalI
No full textRoad maintenance is till today, in many cases, left to improvisation. It is often performed when the pavement has been damaged, through interventions and repairing times based upon previous experience or consolidated practice. The continuous increase in road traffic and stresses on the pavements, the necessity to ensure high safety levels and, moreover, the reduction of the available funds for the Public Administrations impose different and innovative managerial choices. Therefore, repair works need to be planned and executed with the best quality-cost rate, in the shortest time possible and with the smallest discomfort to road users.
The automatic survey technique represents the only possible solution to carry out a modern and efficient Pavement Management System (PMS).
The paper describes a research which defines a systematic method for the analysis and the study of the image acquisition and processing techniques useful to develop a non-destructive automatic system for the maintenance state survey of the pavement and for the management of the optimum interventions in a GIS.
Once defined the procedure to use for image acquisition, the processing was made through operations of segmentation, extraction and classification. After reclassifying the image and vectorializing the cracks, was estimated the entity of the damage.
Furthermore, it was verified how spatial resolution and brightness are fundamental factors for a correct implementation of the entire system.
The ArcGIS proves to be the most suitable support to integrate all the procedures used for imaging elaboration and spatial analysis. This software presents user-friendly interfaces and provides efficient visualizations of surveyed results, not only for the use of transportation engineers (engaged in maintenance management), but also for Road Administrators
Use of Ultra-Thin Whitetopping in the rehabilitation of degraded flexible pavements
No full textThe choice of the most appropriate functional and structural rehabilitation technique for damaged road pavements obviously mainly depends on the type of surface degradation. The most common rehabilitation technique for flexible pavements deals with the resurfacing of the degraded wearing course by means of a bituminous layer, when it can't be completely replaced by similar mixtures.
Nevertheless, maintenance of degraded flexible pavements can be carried out resorting to a different procedure, which is rarely used in Italy, although it is quite popular abroad: Ultra-Thin Whitetopping (UTW). It involves the damaged pavement being resurfaced with small thin cement concrete slabs.
The interaction between the existing bituminous pavement and concrete layer generates a monolithic system, the performance of which is conditioned by various parameters: the volume of vehicular traffic, environmental conditions, the thickness of cement and bituminous concrete layers, the distance between joints, the adhesion between layers and maintenance technique.
The paper describes the results of an Italian application of this technique. The experiments regarded the identification and characterization of the existing bituminous pavements (through cores and bearing capacity tests), the design of the UTW, the cement concrete mix design (PP and SB fibres were added to the mixture to enhance compressive strength and elasticity), the mechanical characterization of the new layer (by means of compressive strength and dynamic modulus), the construction of joints, the execution of loading tests on the slabs and measurement of longitudinal, transversal and vertical deflections by strain gauges and LVDTs.
The study emphasizes the effectiveness of the maintenance technique. The UTW ensures a good bearing capacity to the pavement, thanks to high values of compressive strength and elastic modulus of the concrete, according to future traffic needs. Moreover, deflections are rather limited. Adequate functional properties (evenness, skid resistance) are also guaranteed
Guidelines for an airport safety management system
No full textThe Italian Regulations for airport construction and service, drawn up by ENAC, recommend the airport manager to adopt a Safety Management System (SMS), by the end of 2005.
The SMS is the instrument considered necessary in order to enhance the safety levels in the airport. This need arises from the fact that, in the last few years, air traffic has continuously increased and consequently, airfield operations have similarly grown. This has caused an increase in “runway incursion” phenomena, associated with physical interferences and “contacts” between aircraft manoeuvring in the aprons or taxiways.
This paper highlights that, with the objective of appropriate airport activity, each component of the airport area being designed according to the operational standards of the airport itself it is not sufficient, whereas rules and procedures suitable for different functional scenarios are a necessity for a safe exploitation of the infrastructure.
The paper explains the requirements for a correct airport system implementation: a safety-oriented management approach, an organization effectively based on safety requirements and a system with safety being its main goal.
The paper also presents the guidelines to be followed for drawing up an airport SMS, paying attention to each single phase of the procedures, such as: identification of the objectives to be reached, planning of the intervention priorities, selecting the most suitable procedures to achieve these objectives, evaluation of the performance levels through continuous monitoring of the system condition
Experimental research on the performances of cement bound granular materials containing recycled aggregate
No full textAmong the techniques adopted to stabilise road foundations, the use of cement bound granular materials is worth mentioning: although this technique isn’t properly innovative, it represents a satisfying solution in case a layer with rather contained deformations (produced by heavy vehicular traffic, to which pavement fatigue failure is often associated) is needed.
Up to now, the research has been mainly carried on cement-bound granular mixtures containing natural aggregate. On the contrary, in Italy, researches evaluating the characteristics of cement-bound granular aggregate made by recycled material are still at an early stage. More precisely, it can be stated that, despite the common re-utilisation of recycled material in the building sector (this re-use, especially in the last few years, has aroused growing interest thanks to strong economic reasons and environmental awareness), it is not yet adequately supported by extended scientific knowledge. Furthermore, there is an ever growing need to identify techniques not only to reduce the quantity of milled road material to be conveyed to waste dumps, but also to seek alternative material to be used in road construction, in order to take into account the reduced availability of non-renewable natural resources.
Under these circumstances, the performances of a cement-bound granular mixture containing milled aggregate (from road pavements) have been compared with those of a cement-bound mix containing natural aggregate; for both types of materials the grading curve, dosage of cement, water content and mechanical properties of the mixtures (compressive strength and indirect tensile strength) have been evaluated. The results have been compared with those required in the Specifications and Regulations in force in Italy.
The experimental study has demonstrated that the performances of both mixtures are equivalent and the milled aggregate from road pavements can be used as material for road foundations
- …
