Accident Prediction Models for Freeway Segments and Feasibility Study for Improving the Utilization of TASAS. PDF Download

Author: Jean Gilbertson
Publisher:
ISBN:
Category : Expert systems (Computer science)
Languages : en
Pages : 61

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Author: Yuanlin Huang
Publisher:
ISBN:
Category : Expert systems (Computer science)
Languages : en
Pages : 100

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Author: Nancy Dutta
Publisher:
ISBN:
Category : Traffic accidents
Languages : en
Pages : 0

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Book Description
Crash analysis methods typically use annual average daily traffic as an exposure measure, which can be too aggregate to capture the safety effects of variations in traffic flow and operations that occur throughout the day. Flow characteristics such as variation in speed and level of congestion play a significant role in crash occurrence and are not currently accounted for in the American Association of State Highway and Transportation Officials' Highway Safety Manual. This study developed a methodology for creating crash prediction models using traffic, geometric, and control information that is provided at sub-daily aggregation intervals. Data from 110 rural four-lane segments and 80 urban six-lane segments were used. The volume data used in this study came from detectors that collect data ranging from continuous counts throughout the year to counts from only a couple of weeks every other year (short counts). Speed data were collected from both point sensors and probe data provided by INRIX. The results showed that models that used data aggregated to an average hourly level reflected the variation in volume and speed throughout the day without compromising model quality. Crash predictions for urban segments underwent a 20% improvement in mean absolute deviation for total crashes and a 9% improvement for injury crashes when models using average hourly volume, geometry, and flow variables were compared to the model based on annual average daily traffic. Corresponding improvements over annual average daily traffic models for rural segments were 11% and 9%. Average hourly speed, standard deviation of hourly speed, and differences between speed limit and average speed had statistically significant relationships with crash frequency. For all models, prediction accuracy was improved across all validation measures of effectiveness when the speed components were added. The positive effect of flow variables was true irrespective of the speed data source. Further investigation revealed that the improvement achieved in model prediction by using a more inclusive and bigger dataset was larger than the effect of accounting for spatial/temporal data correlation. For rural hourly models, mean absolute deviation improved by 52% when short counts were added in comparison to the continuous count station only models. The respective value for urban segments was 58%. This means that using short count stations as a data source does not diminish the quality of the developed models. Thus, a combination of different volume data sources with good quality speed data can lessen the dependency on volume data quality without compromising performance. Although accounting for spatial and temporal correlation improved model performance, it provided smaller benefits than inclusion of the short count data in the models. This study showed that it is possible to develop a broadly transferable crash prediction methodology using hourly level volume and flow data that are currently widely available to transportation agencies. These models have a broad spectrum of potential applications that involve assessing safety effects of events and countermeasures that create recurring and non-recurring short-term fluctuations in traffic characteristics.

Author: Albert Gan
Publisher:
ISBN:
Category : Traffic safety
Languages : en
Pages : 170

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Author: Vasin Kiattikomol
Publisher:
ISBN:
Category : Express highways
Languages : en
Pages : 125

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Author: Imalka Chiranthi Matarage
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Crash prediction models in the Highway Safety Manual (HSM) are used to quantify the safety experience of existing and new roadways. Safety performance functions (SPFs) or crash prediction models are statistical formulas developed on limited data from a few selected states, Kansas not being one of those states. Therefore, the HSM recommends calibration of HSM-default SPFs, or development of local SPFs, to enhance accuracy of predicted crash frequency. This dissertation demonstrates the HSM calibration procedure and its' quality assessment for freeway segments, speed-change lanes, ramp segments, and crossroad ramp terminals in Kansas. The study used three years of recent crash data, the most recent geometric data, and HSM-recommended sample sizes for all facilities considered for the calibration. The HSM methodology overpredicted all fatal and injury (FI) crashes and underpredicted all property damage only (PDO) crashes for freeway segments. The HSM methodology consistently underpredicted both FI and PDO crashes for both entrance- and exit-related speed-change lanes. The HSM methodology overpredicted all FI crashes, underpredicted multiple vehicle PDO crashes, and overpredicted single vehicle PDO crashes for entrance ramp segments. In the case of exit ramp segments, the HSM methodology underpredicted all multiple vehicle crashes and overpredicted all single vehicle crashes. The HSM methodology overpredicted all FI crashes and underpredicted all PDO crashes for both signal- and stop-controlled crossroad ramp terminals. Cumulative residual plots and coefficient of variation were used to evaluate the quality of calibrated HSM-default SPFs. Results of calibration quality assessment indicated that estimated calibration factors were satisfactory for all freeway and ramp facilities considered in this study. However, for further accuracy and comparison purposes, calibration functions were developed to improve the fit to local data. Calibration functions were better fitted compared to calibrated HSM-default SPFs for freeway and ramp facilities in Kansas. Challenges faced, how those challenges were addressed, and data collection techniques used in this study are discussed. In summary, estimated calibration factors and developed calibration functions of this study would greatly improve making accurate decisions related to freeway and ramp safety in Kansas.

Author: Petros Ioannou
Publisher: Springer Science & Business Media
ISBN: 1475745737
Category : Technology & Engineering
Languages : en
Pages : 366

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Book Description
Experts address some of the main issues and uncertainties associated with the design and deployment of Automated Highway Systems (AHS). They discuss new AHS concepts, technology, and benefits, as well as institutional, environmental, and social issues - concerns that will affect dramatically the operation of the current highway system from both the vehicle and infrastructure points of view.

Author:
Publisher: AASHTO
ISBN: 1560514280
Category : Pavements
Languages : en
Pages : 87

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Book Description
This report contains guidelines and recommendations for managing and designing for friction on highway pavements. The contents of this report will be of interest to highway materials, construction, pavement management, safety, design, and research engineers, as well as others concerned with the friction and related surface characteristics of highway pavements.

Author: Dean T. Jamison
Publisher:
ISBN:
Category : Medical
Languages : en
Pages : 264

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Book Description
This review of China's health sector begins by noting China's achievements in population control, health status, and nutrition. The policies, sources of financing, and resource use that have contributed to China's successes are cited, and the evolution of several influences on health from outside the sector are discussed, including nutritional improvements, greater access to clean water and sanitary waste disposal, and fertility reduction. Two major challenges now face China's health sector: (i) extending the methods that have been successful to areas where mortality rates and deaths due to infectious diseases remain high; and (ii) developing and implementing approaches to management of chronic disease that combine prevention, low-cost treatment, rehabilitation, and humane care. Major innovation will be essential because resources are limited and plans for meeting the health needs of the population are ambitious. Institutions capable of innovation, experimentation, and analysis of public health problems must be developed. The report includes discussion of specific issues in the sector.

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309124883
Category : Computers
Languages : en
Pages : 377

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Book Description
All U.S. agencies with counterterrorism programs that collect or "mine" personal data-such as phone records or Web sites visited-should be required to evaluate the programs' effectiveness, lawfulness, and impacts on privacy. A framework is offered that agencies can use to evaluate such information-based programs, both classified and unclassified. The book urges Congress to re-examine existing privacy law to assess how privacy can be protected in current and future programs and recommends that any individuals harmed by violations of privacy be given a meaningful form of redress. Two specific technologies are examined: data mining and behavioral surveillance. Regarding data mining, the book concludes that although these methods have been useful in the private sector for spotting consumer fraud, they are less helpful for counterterrorism because so little is known about what patterns indicate terrorist activity. Regarding behavioral surveillance in a counterterrorist context, the book concludes that although research and development on certain aspects of this topic are warranted, there is no scientific consensus on whether these techniques are ready for operational use at all in counterterrorism.