Francisco Calvo

Analysis of traffic accident injury severity on Spanish rural highways using Bayesian networks

Several different factors contribute to injury severity in traffic accidents, such as driver characteristics, highway characteristics, vehicle characteristics, accidents characteristics, and atmospheric factors. This paper shows the possibility of using Bayesian Networks (BNs) to classify traffic accidents according to their injury severity. BNs are capable of making predictions without the need for pre assumptions and are used to make graphic representations of complex systems with interrelated components. This paper presents an analysis of 1536 accidents on rural highways in Spain, where 18 variables representing the aforementioned contributing factors were used to build 3 different BNs that classified the severity of accidents into slightly injured and killed or severely injured. The variables that best identify the factors that are associated with a killed or seriously injured accident (accident type, driver age, lighting and number of injuries) were identified by inference.

Analysis of traffic accidents on rural highways using Latent Class Clustering and Bayesian Networks

One of the principal objectives of traffic accident analyses is to identify key factors that affect the severity of an accident. However, with the presence of heterogeneity in the raw data used, the analysis of traffic accidents becomes difficult. In this paper, Latent Class Cluster (LCC) is used as a preliminary tool for segmentation of 3229 accidents on rural highways in Granada (Spain) between 2005 and 2008. Next, Bayesian Networks (BNs) are used to identify the main factors involved in accident severity for both, the entire database (EDB) and the clusters previously obtained by LCC. The results of these cluster-based analyses are compared with the results of a full-data analysis. The results show that the combined use of both techniques is very interesting as it reveals further information that would not have been obtained without prior segmentation of the data. BN inference is used to obtain the variables that best identify accidents with killed or seriously injured. Accident type and sight distance have been identify in all the cases analysed; other variables such as time, occupant involved or age are identified in EDB and only in one cluster; whereas variables vehicles involved, number of injuries, atmospheric factors, pavement markings and pavement width are identified only in one cluster.

A classification tree approach to identify key factors of transit service quality

A key aspect to take into consideration when developing indices to evaluate transit service quality is to determine how much weight passengers give to each attribute when making a global assessment of service quality (SQ). The simplest method of a direct question in customer satisfaction survey (CSS) poses a number of problems, and therefore statistical regression methods have been developed to infer attribute importance on the basis of CSS or stated preference surveys. However, most regression models have their own model assumptions and pre-defined underlying relationships between dependant and independent variables. If these assumptions are violated, the model could lead to erroneous estimations. This paper proposes using a classification and regression tree (CART) that does not require any pre-defined underlying relationship between dependent and independents variables, to identify the key factors affecting bus transit quality of service. The paper uses the data gathered in a CSS conducted on the Granada metropolitan transit system in 2007, which was a non-research oriented survey. Two CART models were developed to compare the key attributes identified before and after making passengers reflect on the main aspects of the system. The outcomes show that, in a preliminary evaluation, passenger perception of SQ is basically influenced by frequency. After being asked to evaluate all the attributes, however, other attributes (e.g. proximity, speed and safety) become more important than frequency.

Proposed Infrastructure Pricing Methodology for Mixed-Use Rail Networks

A pricing methodology adapted to specific railroad infrastructures and the trains that use them is one way to ensure that railroad networks used by several different operators are used optimally. The diversity of railway networks (new lines and old lines) and services (long-distance and suburban passenger trains, freight trains, etc.) makes it difficult to develop such a pricing methodology. A pricing methodology is proposed for a mixed-use rail network designed to encourage efficient network use and thereby contribute to development of a sustainable transport system. The proposed methodology considers internal and external costs. It could be applied by different network operators (e.g., national rail networks) differently on the basis of policy objectives. One feature of the pricing methodology is that it would partially subsidize a rail services infrastructure charges on the basis of savings in external costs when a certain level of demand is met by railroad rather than road. The proposed methodology also considers the rail service operators willingness to pay and public service issues. How the proposed methodology would be applied for different train services is described. Conclusions show that under the proposed pricing methodology, charges would increase in the following order: suburban, regional passenger trains, and freight trains (lowest) to high-speed trains (highest).

Relationship between Predicted Speed Reduction on Horizontal Curves and Safety on Two-Lane Rural Roads in Spain

According to different studies, speed reduction is considered one of the major factors in contributing road safety. For that reason, several guidelines have been recommended for maximum desirable speed reductions from tangents to horizontal curves and for maximum differentials between design and operating speeds on horizontal curves. The Interactive Highway Safety Design Model (IHSDM) Design Consistency Module presents an analysis of the relationship between speed reduction and crashes for horizontal curves on U.S. two-lane rural highways. This paper presents the relationship between speed reduction and crashes for horizontal curves on Spanish two-lane rural roads. A model for using regression analysis to predict crashes is presented. Exposure, curve length (CL), and difference in 85th-percentile speeds (ΔV85) between successive tangents and horizontal curves, as well as between successive curves, are used. The models coefficients were different from the ones obtained for U.S. highways, although the values of the goodness-of-fit criteria were similar. In addition, the relationship between crashes and different speeds is analyzed, taking the difference in speed as a speed differential not exceeded by 85% of the drivers traveling under free-flow conditions (Δ85V), instead of considering it as ΔV85. The two models (ΔV85 versus Δ85V) give very similar results. Language: en

Opening of the European Railroad Network: A Lost Opportunity for European Unification

The opening of railroad infrastructure to new transport operators in Europe has made it necessary to develop a pricing system for its use. The European Union (EU) has proposed guidelines for establishing a similar pricing system for all EU members. Nonetheless, pricing systems continue to differ substantially from one country to another. These differences reduce continuity between networks and distort the competitive conditions between countries and negatively affect domestic trade. This paper analyzes the pricing systems of eight European countries and presents several proposals for harmonizing them.

How to Expand Subway and Urban Railway Networks: Light Rail Extensions in Madrid, Spain

Residential areas of detached houses were built in north and east Madrid, Spain, during the last decade of the 20th century. Because the population density in those areas is low, implementing an efficient transport system is complicated. In south Madrid in the 1960s, however, huge commuter towns developed. Some of them were linked to a suburban network at some point, whereas others were far away. The Madrid region promoted the construction of several light rail lines to resolve this issue. The lines function as extensions to the existing rail network (subway or suburban trains). The determining factors that enabled these lines to be implemented and operated successfully are analyzed. The recommendations for implementing a light rail transit system, on the basis of that analysis, are: (a) the lines should not be very long; (b) they should have a segregated right-of-way; (c) the quality of service should be good; and (d) they should be coordinated with other modes of transport. Apart from public funding, they could be funded by additional resources collected from property tax and the concessionaire company (private funding). A concessionaire consortium may comprise construction companies, transport operators, financial institutions, rolling stock manufacturers, and consultancies. Finally, the concession should be granted for a 30- to 40-year period so that private stakeholders can recover their investment.

Light Rail Transit Experience in Madrid, Spain: Effects on Population Settlement and Land Use

The development of new transport systems often leads to demographic and socioeconomic changes in the implementation area. The extent and the type of such impacts vary, however, and can depend on existing settlement patterns, socioeconomic conditions, and project objectives. For a better understanding of such impacts better, this paper examines the effects of two new light rail transit lines (ML1 and ML2) in Madrid, Spain. The two lines were planned to serve different functions, and the service areas have different land use characteristics. ML1 was designed to help promote urban development in a lightly settled area, while ML2 was designed to encourage public transport in an already developed area. As expected, the analysis showed that the impacts of these two lines were quite different. Along ML1, much new development took place, and large increases occurred in the population. Along ML2, land use and population remained largely unchanged. This finding demonstrates the critical importance of integrated transport and land use planning in the development of cities.

Proposal of a New Global Model of Consistency: Application in Two-Lane Rural Highways in Spain

Consistency is the relationship between the geometric characteristics of a highway and the conditions a driver expects to encounter. In this study, based on operating speed, consistency was calculated in two-lane rural highways of the province of Granada, Spain. Three consistency measures were calculated for 506 homogeneous road sections: the relative area, which represents the area bounded by the speed profile and average speed of a road segment; the standard deviation of the operating speed in each design element along the road segment; and a consistency model based on the previous measures introduced. Some discrepancies regarding the obtained results lead the authors to propose a new model of consistency that overcomes the identified disagreements.

A proposal for cost-related and market-oriented train running charges

This paper examines some key aspects of a charging system for promoting railway transport, including charges reflecting a clear relationship with costs (transparency) and charges reflecting the quality of the infrastructure managers service. Train running charges recover track-related costs and can help to develop a charging system that meets these requirements. To orient train running charges to the market, a method for processing track maintenance and renewal costs is proposed whereby the quality of the service provided by an infrastructure is measured according to its utility to the railway undertaking. To achieve transparency, a single indicator is used for cost planning and the subsequent levying of costs on railway undertakings. The paper includes an example of how proposed train running charges would be calculated according to data from 14 European countries. The example shows that short-distance trains generate the lowest maintenance and renewal costs, followed by long-distance trains and freight trains.