Related Experiment Video
Updated: Jul 31, 2026
11:41
Evaluation of an Exclusive Spur Dike U-Turn Design with Radar-Collected Data and Simulation
Published on: February 1, 2020
Modeling accident occurrence at signalized tee intersections with special emphasis on excess zeros
1Department of Civil Engineering, National University of Singapore, Singapore. engp0436@nus.edu.sg
Traffic Injury Prevention
|October 3, 2003
Summary
This study uses a zero-inflated negative binomial model to analyze accident data from Singapore intersections. It identifies key geometric and traffic factors influencing crash risk, distinguishing true safety from random chance.
Area of Science:
- Traffic Engineering and Safety
- Transportation Science
- Statistical Modeling in Road Safety
Background:
- Identifying hazardous intersection factors is crucial for effective remedial treatments.
- Distinguishing truly safe intersections from those with no accidents due to random chance is a common challenge in accident studies.
- Accident data analysis often requires specialized models to handle excess zero-accident records.
Purpose of the Study:
- To develop a statistical model for identifying geometric and traffic factors contributing to accident occurrence at signalized intersections.
- To address the issue of 'excess zeros' in accident data by employing a zero-inflated negative binomial model.
- To analyze accident data from 104 signalized tee intersections in Singapore over a 9-year period.
Main Methods:
- Utilized accident data from 104 signalized tee intersections in Singapore spanning 9 years.
- Employed the zero-inflated negative binomial (ZINB) model to account for excess zero-accident records.
- Analyzed the probability of accident outcomes based on various geometric and traffic variables.
Main Results:
- Factors increasing accident occurrence include uncontrolled left-turn slip roads, permissive right-turn phases, horizontal curves, short sight distances, numerous signal phases, and high total/left-turn approach volumes.
- Factors reducing accident occurrence include right-turn channelization, left-turn lane acceleration sections, median railings, and gradients over 5%.
- A discernible trend of decreasing accidents over the study period was observed.
Conclusions:
- The zero-inflated negative binomial model effectively distinguishes between inherently safe intersections and those with no accidents due to chance.
- Specific geometric designs and traffic conditions significantly influence accident risk at signalized tee intersections.
- Findings provide valuable insights for targeted safety improvements and urban traffic management strategies in Singapore.
Related Concept Videos
01:19Routh-Hurwitz Criterion II
In the application of the Routh-Hurwitz criterion, two specific scenarios can arise that complicate stability analysis.
The first scenario occurs when a singular zero appears in the first column of the Routh table. This situation creates a division by zero issues. To resolve this, a small positive or negative number, denoted as epsilon (∈), is substituted for the zero. The stability analysis proceeds by assuming a sign for ∈. If ∈ is positive, any sign change in the first column of the Routh...
The first scenario occurs when a singular zero appears in the first column of the Routh table. This situation creates a division by zero issues. To resolve this, a small positive or negative number, denoted as epsilon (∈), is substituted for the zero. The stability analysis proceeds by assuming a sign for ∈. If ∈ is positive, any sign change in the first column of the Routh...
01:19Introduction to Horizontal Curves
Horizontal curves are essential in highway and railroad design, ensuring smooth and safe transitions between straight path segments, or tangents. These curves allow vehicles to maintain speed without abrupt changes, minimizing accidents and improving travel efficiency.A horizontal curve is typically defined by its geometric relationship to two tangents that meet at an intersection point (P.I.), where a simple curve is introduced to connect them. The back tangent refers to the initial tangent...
01:24Introduction to Vertical Curves
Vertical curves are parabolic transitions that connect different grades on highways and railroads, ensuring a smooth alignment between back and forward tangents. The back tangent represents the initial grade, while the forward tangent defines the subsequent grade. These curves can be symmetrical, with equal tangent lengths, or nonsymmetrical, with varying lengths. The key points defining a vertical curve include the Point of Vertical Intersection (P.V.I.), where the tangents meet; the Point of...
01:23Vertical Curve: Problem Solving
Vertical curves provide the transition between two roadway grades, ensuring safety, comfort, and functionality. Calculating elevations at specific stations along the curve involves several systematic steps based on the curve's geometry and provided design parameters.The vertical curve is defined by its length, grades, Point of Vertical Intersection (P.V.I.) location, and P.V.I. elevation. The stations of the Point of Vertical Curvature (P.V.C.), where the curve begins, and the Point of Vertical...
01:20Elevation of Intermediate Points on Vertical Curves
Vertical curves are essential in roadway design because they provide smooth transitions between varying roadway grades. Designing vertical curves involves calculating intermediate elevations and identifying the curve's highest or lowest point, which is essential for optimal roadway performance.Intermediate elevations on a vertical curve are determined using the tangent offset method. This method considers the initial elevation at the start of the curve, the grades, and the curve's geometry. The...
01:27Real Zeros of Polynomials
Polynomials are algebraic expressions of terms with variables raised to non-negative integer powers. A central aspect of analyzing polynomial functions is determining their real zeros—values of the variable for which the polynomial evaluates to zero. These values represent the x-intercepts of the polynomial’s graph.The Rational Zeros Theorem lists possible rational solutions for a polynomial equation with integer coefficients. If f(x)=anxn+....+a0, then every rational zero is of the form p/q,...