This paper focuses on application of crash prediction models in network screening. The two main questions were ( a) What variables should be involved in the model? and ( b) What length should the modeled period be? Answers to these questions should provide guidelines for developing an updatable crash prediction model (i.e., a model that is both reliable and simple so that its updating for periodical network screening is not highly demanding). Data on approximately 1,000 km (600 mi) of a two-lane rural-road network from South Moravia, Czech Republic, were used. On the basis of 8 years of annual crash frequencies, together with exposure and geometrical variables, several variants of prediction models were developed. To study the quality of the models, a series of consistency tests was applied relative to comparison of the models themselves as well as to their diagnostic performance. As a result, simple crash prediction models (that included traffic volume, segment length, and curvature change rate) were found sufficient for network screening. If one supposes that length and curvature are unlikely to change often, only traffic volume data need to be periodically updated. Consistency analyses indicate that this period should be 4 years. Under these conditions, models are being applied in the studied region. Further planned activities include extensions to intersections and also to other Czech regions.
There is a problem with inappropriate speed consequences related to horizontal alignment of Czech rural roads. Evaluation of alignment consistency, i.e. the degree to which a road is designed and constructed to avoid critical driving manoeuvres, has been known as one of promising tools in this regard. The objectives of presented pilot study were (1) to prove the practical application on historical rural road, lacking design data, using low-cost technology, (2) to investigate the relation of obtained alignment consistency measures to actual safety, and (3) to propose further steps for practical implementation, e.g. for the needs of road agency. Given these objectives and literature review findings, GPS technology was chosen for data collection, with the aim of using alignment consistency levels. Pilot rural road section was approximately 2.5 km long and consisted of 3 straight segments and 3 curves. Data processing included determination of central trajectory, determination of horizontal alignment elements and segmentation, calculation of consistency measures, and identification of inconsistencies. The results are given in terms of the consistency level of individual curves, followed by validation by the results of accident data analysis. In the end, several practical applications are listed and described.
Purpose
Given the inconsistent application of various road markings on Czech rural roads, there is a question “How does road marking in horizontal curves influence driving behaviour?” The study objective was to assess how centreline and edgelines influence driving behaviour.
Methods
To focus on the critical conditions, six curves on secondary rural roads, with radii below 200 m, were selected and monitored before and after application of road marking. The studied indicators were average speed and lateral position, which were collected using trajectories detected in calibrated video recordings.
Results
The results indicated that speeds decreased in both edgeline and centreline applications; regarding lateral positions, the edgelines were associated with shifting the driving trajectories towards the centre of the road, and the centrelines were associated with shifting the driving trajectories towards the road edges.
Conclusions
The indicated trends are likely to be influenced also by other factors, such as specific curve radii values, superelevation, speed profile, or parameters of road surroundings. Following study should thus focus on collecting data in a larger sample of sites and building a cross-sectional model, statistically linking the mentioned characteristics with safety.
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