The recently released Highway Safety Manual (HSM) published by AASHTO provides a comprehensive set of tools for evaluating and identifying opportunities to improve safety for highway facilities. Included in the HSM is a quantitative method for predicting crashes on the basis of recently developed scientific approaches. These predictive methods currently exist for three facility types: rural two-lane roads; rural multilane highways; and urban and suburban arterial highways. To enhance precision, each HSM predictive method should be calibrated for location conditions. This paper demonstrates the HSM calibration procedure for total crashes in Oregon. The research identified three critical data collection limitations on information about pedestrian volumes, minor road traffic volumes at rural locations, and minimum sample size for underrepresented crash locations. Most of the calibration factors for Oregon were determined to be considerably lower than the expected value of approximately 1, and this observation was attributed to Oregon crash reporting thresholds and procedures. The paper includes an evaluation of crash severity distribution methods and an assessment of the significance of collision type distributions on the overall predicted crashes.

Street layout and design, once established, are then not easily changed. Urban form affects community development, livability, sustainability, and traffic safety. There has been an assumed relationship between urban form and traffic safety that favors designs with less through streets to improve safety. An empirical study to test this assumed relationship was carried out for crash data for Portland, Oregon. This thesis presents an empirical methodology for analyzing the relationship between urban form and traffic safety utilizing a uniform grid for the spatial unit. Crashes in the Portland, Oregon city limits from 2005-2007 were analyzed and modeled using negative binomial regression to study the effect of urban form and street layout through factors on exposure, connectivity, transit accessibility, demographic factors, and origins and destinations. These relationships were modeled separately by mode: vehicle crashes, pedestrian and bicycle crashes. Models were also developed separately by crash type and by crash injury severity. The models found that urban form factors of street connectivity and intersection density were not significant at 95% confidence for vehicle and pedestrian crash rates, nor for different crash severity levels, indicating that high connectivity grid street layout may have comparable safety to loops and

The Highway Safety Manual (HSM) was published by the American Association of State Highway and Transportation Officials (AASHTO) in the spring of 2010. Volume 2 (Part C) of the HSM includes safety predictive methods which can be used to quantitatively estimate the safety of a transportation facility. The resulting information can then be used to provide guidelines to identify opportunities to improve transportation safety. The safety performance functions (SPFs) included with this content, however, were developed for several states other than Oregon. Because there are differences in crash reporting procedures, driver population, animal populations, and weather conditions (to name a few), the State of Oregon needs to use calibrated SPFs when applying the HSM procedures to local Oregon facilities. Currently, the predictive methods have been developed for three facility types: rural two-lane two-way roads, rural multilane roads, and urban and suburban arterial roads. In this project, the research team calibrated SPFs for all three facility types based on their historic safety performance in Oregon. The report illustrates methods of site selection, the collection of crash and site-specific data, and analysis methods for calibration. Also, the report includes an evaluation of the crash severity distribution methods. With this information, Oregon agencies can use the calibrated HSM predictive methods to assess expected facility safety performance for Oregon conditions and facility alternatives.17.

Street layout and design, once established, are then not easily changed. Urban form affects community development, livability, sustainability, and traffic safety. There has been an assumed relationship between urban form and traffic safety that favors designs with less through streets to improve safety. An empirical study to test this assumed relationship was carried out for crash data for Portland, Oregon. This thesis presents an empirical methodology for analyzing the relationship between urban form and traffic safety utilizing a uniform grid for the spatial unit. Crashes in the Portland, Oregon city limits from 2005-2007 were analyzed and modeled using negative binomial regression to study the effect of urban form and street layout through factors on exposure, connectivity, transit accessibility, demographic factors, and origins and destinations. These relationships were modeled separately by mode: vehicle crashes, pedestrian and bicycle crashes. Models were also developed separately by crash type and by crash injury severity. The models found that urban form factors of street connectivity and intersection density were not significant at 95% confidence for vehicle and pedestrian crash rates, nor for different crash severity levels, indicating that high connectivity grid street layout may have comparable safety to loops and