Signal Control of Roundabouts

AbstractDuring the last decade many traffic signal controlled intersections have been replaced by roundabouts. There has been a trend towards the establishment of roundabouts where pedestrians and cyclists need to be considered specifically, sometimes by including one or more signal controlled crosswalks. Knowledge on adequate design, control and effects of different solutions, particularly with accessibility and traffic safety in mind, has been limited in Sweden. This lack of knowledge was the basis for a project in 2007 financed by the Swedish National Road Administration and which was divided into two parts. In the first part an inventory of available knowledge on signal controlled roundabouts both in Sweden and abroad was carried out.The following alternative forms of signal control were determined for the projects aspects:A1: Signal controlled crosswalks at the approach and in the direct vicinity of the gyratory (off signal).A2: Signal control of crosswalks at the approach up- and downstream.B1: Complete signal control of an approach. The crosswalks on both directions are passed in a single step.B2: Complete signal control of an approach. The crosswalks are passed in two steps (with intermediate stops).C: Coordinated, fully signal control of the roundabout.In the second part of the project accessibility analysis for the different alternatives was carried out with the help of field studies and calculations using the traffic modeling tool TRANSYT for signal optimization and VISSIM for evaluation of the effects. The traffic safety aspects were analyzed with the aid of specific interviews with the regulatory organizations, accident statistics from STRADA (Swedish Traffic Accident Data Acquisition) and field studies of traffic behavior at two roundabout locations.The project concluded following recommendations regarding accessibility and safety:•Alternative (A1) should be avoided from both a capacity and a traffic safety aspect. Use B.•Alternative (A2) should be placed a minimum of 22 m from the roundabout due to both capacity and a traffic safety aspects.•Alternative (B2), which has higher capacity than (B1) can be applied if there is a need for signalized crosswalks.•Alternative (C) can be considered due to capacity constraints at high pedestrians’ flow of several approaches© 2011 Published by Elsevier Ltd

Updating predictive accident models of modern rural single carriageway A-roads

Reliable predictive accident models (PAMs) are essential to design and maintain safe road networks and yet the models most commonly used in the UK were derived using data collected 20 to 30 years ago. Given that the national personal injury accident total fell by some 30% in the last 25 years, while road traffic increased by over 60%, significant errors in scheme appraisal and evaluation based on the models currently in use seem inevitable. In this paper the temporal transferability of PAMs for modern rural single carriageway A-roads is investigated and their predictive performance is evaluated against a recent data set. Despite the age of these models, the PAMs for predicting the total accidents provide a remarkably good fit to recent data and these are more accurate than models where accidents are disaggregated by type. The performance of the models can be improved by calibrating them against recent data

A space-time multivariate Bayesian model to analyse road traffic accidents by severity

The paper investigates the dependences between levels of severity of road traffic accidents, accounting at the same time for spatial and temporal correlations. The study analyses road traffic accidents data at ward level in England over the period 2005–2013. We include in our model multivariate spatially structured and unstructured effects to capture the dependences between severities, within a Bayesian hierarchical formulation. We also include a temporal component to capture the time effects and we carry out an extensive model comparison. The results show important associations in both spatially structured and unstructured effects between severities, and a downward temporal trend is observed for low and high levels of severity. Maps of posterior accident rates indicate elevated risk within big cities for accidents of low severity and in suburban areas in the north and on the southern coast of England for accidents of high severity. The posterior probability of extreme rates is used to suggest the presence of hot spots in a public health perspective.Areti Boulieri acknowledges support from the National Institute for Health Research and the Medical Research Council Doctoral Training Partnership. Marta Blangiardo acknowledges support from the National Institute for Health Research and the Medical Research Council–Public Health England Centre for Environment and Health. Silvia Liverani acknowledges support from the Leverhulme Trust (grant ECF-2011-576)

Assessing the efficient cost of sustaining Britain's rail network: Perspectives based on zonal comparisons

The objective of this paper is to inform the debate on how efficiency targets for Network Rail (formerly Railtrack) should be set during the 2002/03 Interim Review and beyond. Given the problems experienced during the 2000 Periodic Review, which focused on external benchmarks, we propose an internal benchmarking approach, drawing on data for seven geographical Zones within Railtrack (over the period 1995/96 to 2001/02). Our approach mirrors the yardstick competition method used in other UK regulated industries. Three efficiency measurement techniques are applied to this data (DEA; COLS; SFA). Our results suggest that Railtrack (as a whole) delivered substantial improvements in productivity in the early years after privatisation, although these savings were largely offset by the post-Hatfield cost increases. However, looking forward, Zonal efficiency differences suggest that the company could make significant savings in future years by applying (its own) best practice consistently across the network

Are Britain’s railways costing too much? Perspectives based on TFP comparisons with British Rail: 1963-2002.

Following the Hatfield accident in October 2000, the cost of running Britain’s railways has increased very sharply, leading to considerable debate about whether current cost levels are reasonable. This paper seeks to inform this debate by assessing post-Hatfield cost and TFP levels (2000/01 to 2001/02) against the historical precedents set by British Rail and the early experience of the newly-privatised industry (1963 to 1999/00). The results show that industry cash costs rose by 47% between 1999/00, the last financial year before Hatfield, and 2001/02 - but, surprisingly, with train operating costs (TOCs and freight operators) accounting for 42% of this growth. The results also show that the post-Hatfield cost spike is unprecedented when compared against historical benchmarks, indicating that recent cost rises cannot simply be explained by the investment cycle or so-called “bow-wave” effects. Furthermore, according to the preferred models, post-Hatfield productivity levels are lower than at any time over the last four decades. Analysis of long-term data on quality and safety measures indicates that an excessive focus on rail safety may offer part of the explanation for the recent cost growth, with the emphasis on safety also resulting in less attention to punctuality and reliability

Are speed enforcement cameras more effective than other speed management measures? The impact of speed management schemes on 30mph roads.

This paper presents the results of an evaluation of the impact of various types of speed management schemes on both traffic speeds and accidents. The study controls for general trends in accidents, regression-to-mean effects and migration, separately estimating the accident changes attributable to the impact of the schemes on traffic speed and on traffic volume. It was found that, when judged in absolute terms, all types of speed management scheme have remarkably similar effects on accidents, with an average fall in personal injury accidents of about 1 accident/km/year. In terms of the percentage accident reduction, however, engineering schemes incorporating vertical deflections (such as speed humps or cushions) offer the largest benefits: at 44%, the average reduction in personal injury accidents attributable to such schemes, is twice that at sites where safety cameras were used to control speeds (22%) and they were the only type of scheme to have a significant impact on fatal and serious accidents. Other types of engineering scheme (with a fall of 29% in personal injury accidents) were on average less effective in reducing accidents than schemes with vertical features but more effective than cameras. All types of scheme were generally effective in reducing speeds, with the largest reductions tending to be obtained with vertical deflections and the smallest with other types of engineering schemes

Methodology for development of drought Severity-Duration-Frequency (SDF) Curves

Drought monitoring and early warning are essential elements impacting drought sensitive sectors such as primary production, industrial and consumptive water users. A quantitative estimate of the probability of occurrence and the anticipated severity of drought is crucial for the development of mitigating strategies. The overall aim of this study is to develop a methodology to assess drought frequency and severity and to advance the understanding of monitoring and predicting droughts in the future. Seventy (70) meteorological stations across Victoria, Australia were selected for analysis. To achieve the above objective, the analysis was initially carried out to select the most applicable meteorological drought index for Victoria. This is important because to date, no drought indices are applied across Australia by any Commonwealth agency quantifying drought impacts. An evaluation of existing meteorological drought indices namely, the Standardised Precipitation Index (SPI), the Reconnaissance Drought Index (RDI) and Deciles was first conducted to assess their suitability for the determination of drought conditions. The use of the Standardised Precipitation Index (SPI) was shown to be satisfactory for assessing and monitoring meteorological droughts in Australia. When applied to data, SPI was also successful in detecting the onset and the end of historical droughts. Temporal changes in historic rainfall variability and the trend of SPI were investigated using non-parametric trend techniques to detect wet and dry periods across Victoria, Australia. The first part of the analysis was carried out to determine annual rainfall trends using Mann Kendall (MK) and Sen’s slope tests at five selected meteorological stations with long historical records (more than 100 years), as well as a short sub-set period (1949-2011) of the same data set. It was found that different trend results were obtained for the sub-set. For SPI trend analysis, it was observed that, although different results were obtained showing significant trends, SPI gave a trend direction similar to annual precipitation (downward and upward trends). In addition, temporal trends in the rate of occurrence of drought events (i.e. inter-arrival times) were examined. The fact that most of the stations showed negative slopes indicated that the intervals between events were becoming shorter and the frequency of events was temporally increasing. Based on the results obtained from the preliminary analysis, the trend analyses were then carried out for the remaining 65 stations. The main conclusions from these analyses are summarized as follows; 1) the trend analysis was observed to be highly dependent on the start and end dates of analysis. It is recommended that in the selection of time period for the drought, trend analysis should consider the length xvi of available data sets. Longer data series would give more meaningful results, thus improving the understanding of droughts impacted by climate change. 2) From the SPI and inter-arrival drought trends, it was observed that some of the study areas in Victoria will face more frequent dry period leading to increased drought occurrence. Information similar to this would be very important to develop suitable strategies to mitigate the impacts of future droughts. The main objective of this study was the development of a methodology to assess drought risk for each region based on a frequency analysis of the drought severity series using the SPI index calculated over a 12-month duration. A novel concept centric on drought severity-duration-frequency (SDF) curves was successfully derived for all the 70 stations using an innovative threshold approach. The methodology derived using extreme value analysis will assist in the characterization of droughts and provide useful information to policy makers and agencies developing drought response plans. Using regionalisation techniques such as Cluster analysis and modified Andrews curve, the study area was separated into homogenous groups based on rainfall characteristics. In the current Victorian application the study area was separated into six homogeneous clusters with unique signatures. A set of mean SDF curves was developed for each cluster to identify the frequency and severity of the risk of drought events for various return periods in each cluster. The advantage of developing a mean SDF curve (as a signature) for each cluster is that it assists the understanding of drought conditions for an ungauged or unknown station, the characteristics of which fit existing cluster groups. Non-homogeneous Markov Chain modelling was used to estimate the probability of different drought severity classes and drought severity class predictions 1, 2 and 3 months ahead. The non-homogeneous formulation, which considers the seasonality of precipitation, is useful for understanding the evolution of drought events and for short-term planning. Overall, this model predicted drought situations 1 month ahead well. However, predictions 2 and 3 months ahead should be used with caution. Many parts of Australia including Victoria have experienced their worst droughts on record over the last decade. With the threat of climate change potentially further exacerbating droughts in the years ahead, a clear understanding of the impact of droughts is vital. The information on the probability of occurrence and the anticipated severity of drought will be helpful for water resources managers, infrastructure planners and government policy-makers with future infrastructure planning and with the design and building of more resilient communities

The accident risk of motorcyclists

This report contains the findings of a study to explore and quantify the interacting influences which determine motorcyclist accident liabilities. It was conducted on behalf of Road Safety Division, Department for Transport. The study first reviewed existing data sources to investigate the trends in motorcycling accidents over the last decade or so. The main part of the study was to carry out a survey of nearly 30,000 current motorcyclists in order to explore the relationship between accident risk and variables such as annual mileage, age, experience, journey type, training, personal characteristics of the riders, and the self-reported behaviours and attitudes of the riders. The numbers of accidents reported by riders within the past 12-months of riding were modelled using generalised linear techniques to take into account factors such as mileage, age, experience, bike size and the conditions prevailing when they rode. Models of rider behaviour were developed using other statistical modelling techniques. These models investigated how attitudes/motivations/perceptions and rider style influence rider behaviour, and how rider behaviour influences the likelihood of accident involvement. The influence of age, sex and experience on attitudes and behaviours, and as direct or indirect influences on accidents were also investigated. Accident risk was also directly influenced by the number of miles ridden in the past 12-months. The report makes a number of recommendations for improving the safety of motorcycle riders

Transportation of hazardous materials via pipeline. A historical overview

The transportation of hazardous materials via pipelines is often considered a safer alternative to other transportation modalities such as railway, road and ship. However, pipelines often cross industrial and highly populated areas, so that their failure can pose a significant risk to the surrounding environment and the exposed population: the possible release of flammable and/or toxic materials in such areas can generate catastrophic events with very severe consequences. A number of accidents have actually occurred in the past years, and even when no deaths or injured are reported, significant damages to the surrounding environment often occur. This suggests that, given the extremely wide extension of the network worldwide, and the very high amounts of transported materials, a careful analysis is still required. In addition, the construction of pipelines also involves the contribution of expertise from a range of technical areas. As a consequence, the occurrence of accidents and the impact of their consequences, depend on the combination of a large number of parameters. In the present paper, an analysis of data relative to pipelines transporting hazardous materials has been carried out, and the influence of specific issues connected with their type and operation, has been assessed