scholarly journals New geometric design consistency model based on operating speed profiles for road safety evaluation

2013 ◽  
Vol 61 ◽  
pp. 33-42 ◽  
Author(s):  
Francisco J. Camacho-Torregrosa ◽  
Ana M. Pérez-Zuriaga ◽  
J. Manuel Campoy-Ungría ◽  
Alfredo García-García
Keyword(s):  
Road Safety ◽  
Safety Evaluation ◽  
Geometric Design ◽  
Operating Speed ◽  
Model Based ◽  
Consistency Model ◽  
Design Consistency

scholarly journals New Consistency Model Based on Inertial Operating Speed Profiles for Road Safety Evaluation

2018 ◽  
Vol 144 (4) ◽  
pp. 04018006 ◽  
Author(s):  
David Llopis-Castelló ◽  
Francesco Bella ◽  
Francisco Javier Camacho-Torregrosa ◽  
Alfredo García
Keyword(s):  
Road Safety ◽  
Safety Evaluation ◽  
Operating Speed ◽  
Model Based ◽  
Consistency Model

Time-Based Calibration of the Inertial Operating Speed to Enhance the Assessment of the Geometric Design Consistency

2018 ◽  
Vol 2672 (38) ◽  
pp. 223-232 ◽  
Author(s):  
David Llopis-Castelló ◽  
Francesco Bella ◽  
Francisco Javier Camacho-Torregrosa ◽  
Alfredo García
Keyword(s):  
Human Factors ◽  
Short Term Memory ◽  
Weighted Average ◽  
Geometric Design ◽  
Accurate Estimation ◽  
Operating Speed ◽  
Speed Profile ◽  
Consistency Model ◽  
Global Consistency ◽  
Design Consistency

Road crashes are mainly caused by three concurrent factors: infrastructure, vehicle, and human factors. The interaction between the infrastructure and human factors leads to the concept of geometric design consistency. Recently, a global consistency model was developed based on the difference between the inertial operating speed profile and the operating speed profile. The first was defined as the weighted average operating speed of the previous road section based on distance, and represents drivers’ expectancies, whereas the second represents road behavior. However, drivers’ expectancies are related to short-term memory which declines gradually and depends on time. Thus, a time-based inertial operating speed would allow a more accurate estimation of the phenomenon. This research analyzes different periods of time and weighting distributions to identify how drivers’ expectancies should be estimated. A set of 71 homogeneous road segments located in Italy were considered in the study. As a result, 25 seconds and a convex parabolic distribution should be used to calculate the inertial operating speed profile. This new way of estimating drivers’ expectancies showed better results than those obtained based on distance. Finally, the proposed consistency model was compared with the previous models and was found to be able to assess more accurately the geometric design consistency. Therefore, the proposed consistency model is a useful tool for engineers to estimate the number of crashes so that they can incorporate road safety considerations into the geometric design of either new two-lane rural roads, or improving the existing ones.

scholarly journals COUNTERMEASURES TO IMPROVE ROAD ALIGNMENT CONSISTENCY OF UNDIVIDED RURAL ROADS

2017 ◽  
Vol 12 (4) ◽  
pp. 211-217 ◽  
Author(s):  
Francesca Russo ◽  
Salvatore Antonio Biancardo
Keyword(s):  
Evaluation Process ◽  
Weather Conditions ◽  
Operating Speed ◽  
Speed Profile ◽  
Negative Exponential Function ◽  
Crash Rates ◽  
Consistency Model ◽  
Global Consistency ◽  
Design Consistency ◽  
Circular Curves

The research aims to assess the relationships between the crash rates and road consistency. Design consistency assessment is a tool employed by designers to improve road safety. The case study involved a rural two-lane two-way road in Southern Italy located on a flat terrain without spiral transition curves between tangent segments and circular curves. Road alignment consistency was examined in two steps: by adopting standards in force in Italy based on the design speed profile and by plotting operating speed profile to determine the area bounded by the speed profile and the average weighted speed, and the standard deviation of operating speeds for each geometric segment. Operating speed prediction model, which returns the 85th percentile of the speed distribution of the only cars under free flow conditions, right weather conditions, and lighting was adopted. A negative exponential function was performed to predict the global consistency of a road as a whole. Finally, a model for predicting the crash rate was calibrated, confirming an increase of design consistency when the crash rates decrease significantly. The consistency model represents a useful tool during the geometric design process or the evaluation process for two-lane rural highways.

Formulation and Validation of Operating Speed-Based Design Consistency Models by Bootstrapping

1997 ◽  
Vol 1579 (1) ◽  
pp. 97-103 ◽  
Author(s):  
John McFadden ◽  
Lily Elefteriadou
Keyword(s):  
Additional Data ◽  
Original Data ◽  
Statistical Technique ◽  
Geometric Design ◽  
Operating Speed ◽  
Horizontal Alignment ◽  
Alternative Means ◽  
Design Speed ◽  
Design Consistency ◽  
Consistency Models

Current U.S. policy for designing rural two-lane highways is based on design speed to ensure consistency among consecutive highway segments. The design speed concept, however, does not ensure that a consistent alignment will be achieved. A recent FHWA-sponsored project (Horizontal Alignment Design Consistency for Rural Two-Lane Highways) led to three operating speed-based geometric design consistency models, which have not yet been validated. Traditionally, the validation of such models involves the collection of additional data. The statistical technique known as “bootstrapping” was used to formulate and validate the operating speed-based geometric design consistency models by using the existing FHWA database. Bootstrapping involves random sampling with replacement from the existing database, which becomes the population. One-half of the original data collected are used in formulating the models. The remaining half of the data are subsequently used for validation. The models resulting from bootstrapping were statistically equivalent to the models developed in the FHWA study. In addition, the model validation indicated that the bootstrapping technique used to validate the operating speed models is a viable alternative means of validation. It was concluded that bootstrapping is a very useful tool that can be exploited in many related areas in the transportation field, especially because of the large amounts of data typically required in developing and validating empirical models.

scholarly journals Research on the Safety Audit Methods for Two-Lane Highway Based on HRV

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Zhan-dong Zhu ◽  
Ying-chih Lu ◽  
Cheng-hong Fu ◽  
Ting Xu
Keyword(s):  
Velocity Gradient ◽  
Road Safety ◽  
Evaluation Criteria ◽  
Safety Evaluation ◽  
Operating Speed ◽  
Acceleration Rate ◽  
Design Speed ◽  
Route Safety ◽  
The Relationship ◽  
Speed Gradient

In order to explore stable route safety evaluation indicators, this study discusses the relationship between the heart rate variability (HRV) and other factors, such as design speed, operating speed, acceleration rate, and velocity gradient through a lot of experiments. The results show that operating speed coordination and velocity gradient (Gv) outperform others as road safety indicators. Speed coordination evaluation criteria:|ΔV85|≤10 km/h, good coordination; 10 km/h≤|ΔV85|≤ 20 km/h, general coordination, route indicators of adjacent sections should be adjusted, so that the speed difference is not more than 10 km/h;|ΔV85|≥20 km/h, poor speed coordination, it needs to readjust the design of the adjacent sections. Speed gradient evaluation criteria:Gv≤0.10, good road safety;0.10≤Gv<0.15, common road safety;Gv>0.15, poor road safety and the adjacent sections need to readjust. The conclusions provide the theoretical reference for highway safety evaluation.

Effect of geometric design consistency on road safety

2004 ◽  
Vol 31 (2) ◽  
pp. 218-227 ◽  
Author(s):  
Joanne C.W Ng ◽  
Tarek Sayed
Keyword(s):  
Road Safety ◽  
Prediction Models ◽  
Model Development ◽  
Geometric Design ◽  
Highway Design ◽  
Rural Highways ◽  
Accident Prediction ◽  
Design Characteristics ◽  
Design Consistency ◽  
The Impact

Geometric design consistency is emerging as an important rule in highway design. Identifying and treating any inconsistency on a highway can significantly improve its safety performance. Considerable research has been undertaken to explore this concept including identifying potential consistency measures and developing models to estimate them. However, little work has been carried out to quantify the safety benefits of geometric design consistency. The objectives of this study are to investigate and quantify the relationship between design consistency and road safety. A comprehensive accident and geometric design database of two-lane rural highways is used to investigate the effect of several design consistency measures on road safety. Several accident prediction models that incorporate design consistency measures are developed. The generalized linear regression approach is used for model development. The models can be used as a quantitative tool for the evaluation of the impact of design consistency on road safety. An application is presented where the ability of accident prediction models that incorporate design consistency measures is compared with those that rely on geometric design characteristics. It is found that models that explicitly consider design consistency may identify the inconsistencies more effectively and reflect the resulting impacts on safety more accurately than those that do not.Key words: geometric design consistency, road safety, quantification, accident prediction models.

Operating speed models for two-lane rural roads in Pakistan

2008 ◽  
Vol 35 (5) ◽  
pp. 443-453 ◽  
Author(s):  
Rizwan A. Memon ◽  
G. B. Khaskheli ◽  
A. Sami Qureshi
Keyword(s):  
Global Positioning System ◽  
Prediction Models ◽  
Geometric Design ◽  
Operating Speed ◽  
Rural Roads ◽  
Horizontal Curves ◽  
Measuring Devices ◽  
Global Positioning ◽  
Speed Prediction ◽  
Design Consistency

One of the suitable techniques used to improve safety on roads is to check the consistency of geometric design. The concept of design consistency has emerged worldwide, but no research has been found to date on design consistency in Pakistan. The most common parameter for the evaluation of design consistency is operating speed. Several models have been developed to predict operating speed on two-lane rural roads. However, these models were based on spot speed data collected through traditional speed measuring devices. This study uses continuous speed profile data collected using a vehicle equipped with a VBox (a global positioning system based device). Eleven test sections were selected in two provinces of Pakistan (i.e., Sindh and Balochistan). Driver behavior is also studied in the present research. Models were developed for prediction of operating speed on horizontal curves and on tangents. Validation of the developed models shows compatibility with the experimental data; hence, the developed speed prediction models can be used to evaluate the geometric design consistency of two-lane rural roads in Pakistan.

scholarly journals OPERATING SPEED PREDICTION MODEL AS A TOOL FOR CONSISTENCY BASED GEOMETRIC DESIGN OF FOUR-LANE DIVIDED HIGHWAYS

Transport ◽  
2019 ◽  
Vol 34 (4) ◽  
pp. 425-436 ◽  
Author(s):  
Gourab Sil ◽  
Avijit Maji ◽  
Suresh Nama ◽  
Akhilesh Kumar Maurya
Keyword(s):  
Prediction Model ◽  
Lateral Position ◽  
Geometric Design ◽  
Operating Speed ◽  
Vehicle Speed ◽  
Horizontal Curve ◽  
Passenger Cars ◽  
Horizontal Curves ◽  
Speed Prediction ◽  
Design Consistency

Researchers have studied two-lane rural highways to predict the operating speed on horizontal curves and correlated it with safety. However, the driving characteristics of four-lane-divided highways are different. Weak lane discipline is observed in these facilities, which influences vehicle speed in adjacent lane or space. So, irrespective of its lane or lateral position, vehicles in four-lane divided highways are considered free flowing only when it maintains the minimum threshold headway from any lead vehicle. Examination of two conditions is proposed to ensure the free flow. Vehicles meeting both conditions, when tracked from the preceding tangent section till the centre of the horizontal curve, are considered as free flowing. The speed data of such free flowing passenger cars at the centre of eighteen horizontal curves on four-lane divided highways is analysed to develop a linear operating speed prediction model. The developed model depends on curve radius and preceding tangent length. The operating speed of passenger car in four-lane divided highways is influenced by horizontal curve of radius 360 m or less. Further, longer tangent would yield higher operating speed at the centre of the curve. Finally, two nomograms are suggested for conventional design, consistency based design and geometric design consistency evaluation of four-lane divided horizontal curves.

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