1,721,089 research outputs found
Analysis of the effects of the cross-section width on dirver’s behaviour from driving simulation
No full text
New model to estimate speed differential in tangent-curve transition
No full textAn experimental study was conducted to define a new model for estimating the speed differential value
between tangents and curves, based on the speed profile of each driver along the tangent-curve transitions.
The CRISS (Inter-University Research Center for Road Safety) interactive fixed-base driving simulator was
used. A predicting model of the speed differential was developed by regression analysis of data recorded in
16 tangent–curve configurations. It shows that the speed differential value depends on the operating speeds,
on the approach tangents and on the curve radius. The model was subsequently verified with the data
recorded in 5 configurations of a real two-lane rural road reconstructed in the driving simulator. The
comparative analysis of the proposed model and the predicting models available in literature shows that the
new model avoids some criticalities of the previous models and is fully consistent with the expected driver
behavior in the tangent - curve transition
Sull’influenza della marcia a plotoni nella determinazione degli standard di progetto: la distanza di visibilità per il sorpasso
No full textDriver Perception of Crest and Sag Combinations at the Driving Simulator: Effects on Drivers’s Behaviour
No full textSeveral researches have pointed out that optical illusions may occur when the horizontal curve is combined with a vertical curve. Crest and sag combinations can cause a significant different driver’s behaviour compared to the behaviour adopted on the horizontal curves on flat grade. In particular the literature reports the hypothesis that horizontal curves appear sharper or flatter when overlapping with crest o sag vertical curves, respectively. This hypothesis was validated from studies on the visual perception of the road through the use of computer animation techniques. On the basis of these researches models were proposed to estimate the horizontal radius perceived on the combined curve as a function of the actual horizontal radius to evaluate the operating speed through 2-D predicting models.
A drawback of computer animation techniques though is that they are limited and not interactive. Interactive driving simulation systems, on the contrary, have high potentials for the analysis of the effects of the combined alignment.
An experimental survey at the driving simulator of CRISS (Interuniversitary Research Center on Road Safety) was carried out in order to assess the driver’s behaviour on crest and sag combinations, compared to the behaviour on horizontal curve with the same radius but on flat grade. Two road alignments for the experiment were designed according to the technical Italian guidelines on the coordination of horizontal curves overlapping with vertical curves. One alignment had a flat longitudinal grade, the other had three crest combinations and three sag combinations but with the same horizontal alignment. The vertical grade on the approach tangent of each combined curve was flat in order to avoid the influence of the grade on driver’s behaviour. 35 drivers carried out two driving sessions at the simulator (one for each road alignment) during which the local speeds and the local lateral placement were recorded.
On the crest combinations the result of statistical analysis of the speeds was entirely consistent with the hypothesis of perception on crest combinations: at beginning of the circular curve on the reference curves the speeds are greater than those on the correspondent crest combinations. Furthermore the outcomes of the unilateral Z-test showed that the differences between the speeds on reference curves and those on crest combinations tend to decrease as the curve radius increases. Also the influence of the crest vertical curve on the trajectory was clear: the mean deviations from the ideal trajectory at the beginning of the circular curve with radii medium and great were significantly higher on the crest combinations than the mean deviations recorded on the reference curves.
On the sag combinations the speeds were not significantly higher (at 5% significance level) than those on the correspondent reference curves. Such result does not seem to strengthen the hypothesis of perception on sag combinations and suggests that the models to estimate the horizontal radius perceived on the sag combinations as a function of the actual horizontal radius to evaluate the operating speed through 2-D predicting models are inappropriate. No significant effect of the sag vertical curve was observed on the trajectory
Operating speed predicting models on two-lane rural roads from driving simulation
No full textThis paper shows the results of an experimental survey carried out using the interactive driving
simulator of the Interuniversitary Research Center on Road Safety with the objective of: evaluating how crosssection
width affects driving speed; validating the data obtained from simulation in order to define predicting
models for operating speed (V85); proposing new predicting models for V85, differentiated for cross-section
width. An alignment of a two -lane rural road was designed and implemented in a driving simulator with three
cross-section widths. 32 drivers were selected in order to have a homogeneous set of people. Each driver
performed the simulation drivings on the three two-lane rural roads with different cross-sections. The speeds
were sampled every 5 meters along the alignment. The analysis of data highlighted how the driver’s choice of
speed is affected by cross-section width. The way the driver adjusts his speed on the different design elements
along the alignment is not affected by the cross-section width but only by geometry of axis of the alignment. In
order to predict operating speed, the validation of the data recorded in driving simulations was performed
through a comparison of the simulation results against Lamm-Institute for Highway and Railroad Engineering
model. The study proposes some relationships between Curvature Change Rate of the Single circular curve with
transition curves (CCRs) and V85 to predict operating speed on two-lane rural roads with different cross-section
widths
Can driving simulators contribute to solving critical issues in geometric design?
No full textResearch on driving simulation in virtual reality has not been recommended
by strategic documents for solving critical issues in geometric
design. However, several research efforts have demonstrated the
usefulness of driving simulators in road design. The objective of this
paper is to initiate a discussion on the effective contribution of driving
simulators to issues of geometric design. The paper gives an overview
of the main experiences acquired in geometric design using advanced
driving simulators and points out their potential as well as their
limits. It then outlines the critical issues in promoting their use in
geometric design and provides recommendations for overcoming
these issues
Safety in Work Zones: Experiences with Driving Simulator
No full textInterferences caused by work zones with vehicle flow can lead to a significant
increase in the accident risk level. It is agreed that the improvement of work zone design is
essential in order to provide an optimal driver guidance. This work reports on the outcomes
of an experimental survey accomplished with the aid of virtual reality and with the aim of
analysing the drivers behaviour close to work zones, identifying eventual abnormal
behaviours and finding useful measures able to avoid a local decrease in safety conditions.
A sample of drivers, homogeneous as far as driving experience, carried out several virtual
reality driving tests on four-lane highways (with two lanes in each direction) using the
driving simulator at the Inter-university Research Centre on Road Safety (CRISS) placed at
University of Rome 3. The surveyed scenarios include a work zone configured according to
the scheme for temporary signalling for work zones as defined in the Italian rules and three
alternative work zone configurations. Speed analysis in various areas of a work zone
allowed to individuate anomalous behaviours. This paper provides the designer with useful
suggestions to choose the safest and most effective work zone design
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