Statistics for Spatial Data.

Principles and Practice of Structural Equation Modeling (2nd ed.)

Highway Capacity Manual改訂の動向--テイラ-教授の講演より

Bayesian Data Analysis (2nd ed.) (Book)

Identifying crash “hotspots”, “blackspots”, “sites with promise”, or “high risk” locations is standard practice in departments of transportation throughout the US. The literature is replete with the development and discussion of statistical methods for hotspot identification (HSID). Theoretical derivations and empirical studies have been used to weigh the benefits of various HSID methods; however, a small number of studies have used controlled experiments to systematically assess various methods.

Using experimentally derived simulated data—which are argued to be superior to empirical data, three hot spot identification methods observed in practice are evaluated: simple ranking, confidence interval, and Empirical Bayes. Using simulated data, sites with promise are known a priori, in contrast to empirical data where high risk sites are not known for certain.

To conduct the evaluation, properties of observed crash data are used to generate simulated crash frequency distributions at hypothetical sites. A variety of factors is manipulated to simulate a host of ‘real world’ conditions. Various levels of confidence are explored, and false positives (identifying a safe site as high risk) and false negatives (identifying a high risk site as safe) are compared across methods. Finally, the effects of crash history duration in the three HSID approaches are assessed.

The results illustrate that the Empirical Bayes technique significantly outperforms ranking and confidence interval techniques (with certain caveats). As found by others, false positives and negatives are inversely related. Three years of crash history appears, in general, to provide an appropriate crash history duration.

Experimental evaluation of hotspot identification methods

A comparison of collision-based and conflict-based safety evaluations: The case of right-turn smart channels

The Highway Safety Manual (HSM) provides an algorithm and associated knowledge to predict crashes on different types of facilities. This algorithm requires calibration to current local conditions through a procedure prescribed in the HSM to enhance its transferability. However, no procedure assesses the transferability. To fill this void, this paper focuses on a methodology to assess the transferability of the key HSM algorithm components—the baseline safety performance function and the crash modification factors (CMFs)—and uses the Italian road network as an illustrative case study. The calibration of the HSM crash prediction model is investigated with a data set for two-lane two-way rural highways to demonstrate some tools that could be used by jurisdictions around the world to assess the validity and compatibility of the CMFs and the base models, as well as the performance of the complete algorithm. A comparison with the results from a similar study carried out in Canada is provided to supplement the c...

/pdf/assessing-international-transferability-of-highway-safety-1pg7eguelj.pdf

Assessing International Transferability of Highway Safety Manual Crash Prediction Algorithm and Its Components

Investigation of models for relating roundabout safety to predicted speed

In road safety analysis, safety performance functions (SPFs) are used to predict the average number of collisions per year at a road site. SPFs are a function of various amounts of exposure and, in some cases, site-specific characteristics. Exposure is a measure of opportunities for collisions to occur. The circulating traffic volume is commonly adopted for this purpose. However, not all vehicles interact unsafely at a road site. Alternatively, traffic conflicts may provide a more appropriate exposure measure for collisions because they represent only unsafe interactions between vehicles. There has been some research on this topic, mainly based on aggregated data including all conflict types. In this study a stratified analysis was conducted by type of conflict. Hence, the main objectives of this research were to establish a relationship between predicted collisions and predicted conflicts by using an SPF with traffic conflicts as an exposure measure and to predict the number of specific types of conflict...

Emanuele Sacchi

Papers

A comparison of collision-based and conflict-based safety evaluations: The case of right-turn smart channels

Assessing International Transferability of Highway Safety Manual Crash Prediction Algorithm and Its Components

Investigation of models for relating roundabout safety to predicted speed

Conflict-Based Safety Performance Functions for Predicting Traffic Collisions by Type

Collision modification functions: incorporating changes over time.