SafeTREC at TRB 2015

December 19, 2014



8:30 a.m. - 10:15 a.m., Convention Center, Hall E
“Variations in Teens’ Perception of Risk Factors for Teen Motor Vehicle Collision Injuries”
Katherine L. Chen, Jill F. Cooper, and Offer Grembek, University of California, Berkeley, SafeTREC, and Russell H. Henk and Stacey Tisdale, Texas A&M Transportation Institute
Presentation: 15-4905; Poster Board Location: J21
Abstract: Teen drivers, especially males, are known to be at greater risk of being involved in a motor vehicle collision than any other age group. While novice teen drivers’ primary risk factors are commonly known, less is known about what teens perceive as risk factors for peers getting hurt or killed in motor vehicle collisions. This study uses survey data from the Teens in the Drivers Seat (TDS) program in California to explore (1) teens' perceived risk factors for motor vehicle collision injury; and (2) the relationship between perceived risks and age, gender, and driving experience. Findings may inform future program development and expansion for TDS and other teen driver safety programming.

10:45 a.m.-12:30 p.m., Convention Center, Hall E
“Complete Streets: From Policy to Practice in the San Francisco Bay Area”
Swati Pande, University of California, Berkeley, SafeTREC, and Martin Martinez, Safe Routes to School National Partnership
Presentation: 15-4299; Poster Board Location: E05
Abstract: The Metropolitan Transportation Commission (MTC) is the regional Metropolitan Planning Organization for the nine county Bay Area region in California. MTC has developed a funding approach called the OneBayArea Grant (OBAG) for the allocation of funds for the 2012-2016 Congestion Mitigation and Air Quality (CMAQ) and Surface Transportation Program (STP) across the Bay Area. All jurisdictions receiving funding through OBAG were required to demonstrate compliance with Complete Streets (CS) either by passing a resolution or by certifying that their General Plan circulation element was compliant with California’s Complete Street Act of 2008. This analysis examines the extent and form of this compliance. The OBAG framework allocated significantly more funding to County Congestion Management agencies as compared to the prior CMAQ/STP cycle (Cycle 1 CMAQ). It also gave counties increased flexibility in decision making by removing program specific silos that were present Cycle 1 CMAQ. This increased flexibility has resulted in an increase in multi-modal projects funded under the Transportation for Livable Communities program. OBAG’s regional funding requirements for Complete Street compliance through policy have the potential to influence Complete Streets implementation by local agencies in the long term.

10:45 a.m.-12:30 p.m., Convention Center, Hall E
“Analysis of Right-of-Way for Different Road Users in China: Passing-Passenger Unit Versus Passenger-Car Unit”
Wen Xiong, Beijing University of Technology, China; Yuanyuan Zhang, University of California, Berkeley, SafeTREC; Xiaohong Chen, Tongji University, China; and Chao Jiang, Beijing University of Technology, China
Presentation: 15-4579; Poster Board Location: E08
Abstract: Being a public resource, the roadway space was distributed between different road users based on the Passing Car Unit (PCU) concept. However, this concept tends to under estimate the capacity of public transportation and non-motorized travel. To improve the traditional car-oriented design to become more human-oriented, this study proposed a Passing-passenger-unit (PPU) and the method to observe the PPU in roadway level and area level. The PPU data were collected for urban arterials and residential areas in China to test the method and to compare the right-of-way distribution at different types of locations. Results showed that the PPU revealed the true efficiency of the facility carrying passengers. Using PPU would tell a different story about the facility or system compared to using PCU. Additionally, using PPU to analyze the right-of-way for the roadway or community could offer guidance for improving pedestrian and bicyclist environment.

2:00 p.m. - 3:45 p.m., Convention Center, Hall E
“Evaluation of Accuracy of Global Positioning System Coordinates for Collision Locations in California”
John M. Bigham, Garrett Strang, and Sang Hyouk Oum, University of California, Berkeley, SafeTREC
Presentation: 15-1278; Poster Board Location: C17
Abstract: Traffic collision reports typically provide descriptive locations indicating where a collision occurred and referencing the nearest intersection. Global Positioning System (GPS) technology can be used to provide latitude and longitude coordinates in addition to the descriptive location and many states now include GPS coordinates in collision reports. However, research has shown that there is potential for numerous errors when police agencies use GPS to complete traffic collision reports. In California, GPS coordinates have been included in the statewide collision database since 2006, but their overall accuracy has never been evaluated. The objective of this paper was to review the status of GPS coordinates in California collision data from 2009 to 2011 and to categorize types of errors or discrepancies that were exhibited, investigate error trends, and develop recommendations for use of the GPS coordinates. Instead of just classifying a GPS coordinate location as correct or incorrect, eleven categorizations were developed to better assess the breadth of differences between the GPS coordinate and descriptive location. Overall, 43% of GPS coordinates were categorized as correct, 2.5% were unknown, and the other 54.5% exhibited some type of discrepancy with the descriptive location. GPS coordinates located off the roadway were the most frequent error type, comprising nearly 20% of the sample, while systematic GPS errors such as truncated coordinates occurred 7% of the time. Accuracy appears to be improving over time, but it is recommended to thoroughly review the coordinate locations prior to conducting any spatial analyses.

7:30 p.m. - 9:30 p.m. Convention Center, 151B
“Traffic Injury on Tribal Lands in California”
David R. Ragland, John M. Bigham, Sang Hyouk Oum, Katherine L. Chen, and Grace Felschundneff, University of California, Berkeley, SafeTREC
Presentation: 15-5824
Abstract: There is a disproportional risk of motor vehicle death and injury among American Indian/Alaska Native (AI/AN) populations in the United States. As home to the nation’s largest population of AI individuals, it is vital that California develop a better understanding of the factors contributing to this risk to guide the development and implementation of interventions to improve traffic safety for this population on the nearly 100 Rancherias and reservations in the state. However, there is very little data about the numbers and types of collisions, and driver and environmental factors contributing to the collisions that occur on tribal lands. As a first step toward better understanding the scope of the risk disparity, and the shortcomings in data collection, SafeTREC conducted a literature review and crash analysis using data from the Statewide Integrated Traffic Record System (SWITRS) and tribal area base maps targeting these communities. As a result of presentations and discussions at a California Tribal Safety conference where these analyses were presented, a number of procedural and institutional challenges were identified. Addressing these issues will not only help policymakers identify interventions to improve traffic safety on tribal lands, but it will give tribal jurisdictions tools to compete for scarce safety funding through the use of data documenting the need for safety improvements. Future research efforts should be aimed at refining these and other initiatives to address both the dire conditions of traffic safety on California’s tribal lands, and the limitations of the data.


8:30 a.m. - 10:15 a.m., Convention Center, Hall E
“Limitations of Data on Cell Phone Involvement in Collisions: A Case Study of California”
Julia B. Griswold and Offer Grembek, University of California, Berkeley, SafeTREC
Presentation: 15-4547; Poster Board Location: I14
Abstract: With the increasing prevalence of mobile technology and high-profile crashes bringing attention to distracted driving, data on cell phone involvement in collisions is critical for understanding the extent of the problem, examining the effectiveness of policies, and developing interventions to improve safety. Some limitations of existing data have been previously identified, but this paper examines the specific case of California’s collision data. Temporal, geographic, and jurisdictional trends are analyzed to identify the source and type of inconsistencies in the cell phone involvement data. Matching and comparison of state and federal data sources highlight further limitations. Data could be improved by simplifying the California crash report form and aligning variables to be more consistent with federal standards. In the meantime, it is not recommended that existing data on cell phone involvement in collisions be used for any analyses to evaluate policy or driver behavior.

2:00 p.m. - 3:45 p.m., Convention Center, Hall E
“Unintended Greenhouse Gas Consequences of Lowering Level of Service in Urban Transit Systems”
Julia B. Griswold, University of California, Berkeley, SafeTREC, and Han Cheng, Samer Michel Madanat, and Arpad Horvath, University of California, Berkeley
Presentation: 15-1843; Poster Board Location: D10
Abstract: Public transit is often touted as a “green” transportation option and a way for users to reduce their environmental footprint by avoiding automobile emissions, but that may not be the case when systems run well below passenger capacity. In previous work, we explored an approach to optimizing the design and operations of transit systems for both costs and emissions, using continuum approximation models and assuming fixed demand. In this paper, we expand upon our previous work to explore how the level of service for users impacts emissions. We incorporate travel time elasticities into the optimization to account for demand shifts from transit to cars, resulting from increases in transit travel time. We find that emissions reductions are moderated, but not eliminated, for relatively inelastic users. We consider two scenarios: the first is where only the agency faces an emissions budget; the second is where the entire city faces an emissions budget. In the latter scenario, the emissions reductions resulting from reductions in transit level of service are mitigated as users switch to automobile.


8:00 a.m. - 9:45 a.m. Convention Center, 151A
“A Database For Active Transportation Infrastructure And Volume”
Frank Roland Proulx, Yuanyuan Zhang, and Offer Grembek, University of California, Berkeley, SafeTREC 
Presentation: 15-5521
Abstract: Information about pedestrian infrastructure and volume is indispensable to monitoring, evaluating, and improving the environment for comfortable and safe walking. However, determining and organizing the various types of data in a way that is easy to update and analyze can present challenges. This study designed and developed a relational database for pedestrian infrastructure and volume, and comprises two core components (node table and approach table) and several sub-components (tables for crosswalks, sidewalks, buffers, signs, transits, bikeways, bicycle parking, and volumes). Important measurements were proposed based on the literature and practice review and grouped into different component categories based on their attributes and relationships. To connect all the components, links were defined according to their relative locations. To prove the feasibility of the database, an infrastructure data collection pilot was conducted across 100 miles of California highways using computer imagery, and across seven miles of highways using field inventory. Time costs associated with collecting infrastructure data for the entire State Highway System were estimated to be 4,006 hours and 8,935 hours for using computer and field collection methods respectively. This study demonstrates that the database is easy to maintain, flexible to update, and feasible for data collection both via computer imagery and in the field. Although most of the data in the database is related to pedestrian, basic bicyclist related information is also included to demonstrate the transferability of the database to store bicyclist infrastructure and volume in the future.

8:00 a.m. - 9:45 a.m. Convention Center, 143A
“Evaluation of Safe Routes to Transit Program in California”
David Weinzimmer, University of California, Berkeley, SafeTREC; Rebecca L. Sanders, University of Oklahoma; and Heidi Dittrich and Jill F. Cooper, University of California, Berkeley, SafeTREC
Presentation: 15-0934
Abstract: This paper elaborates on findings from an evaluation of the San Francisco Bay Area’s Safe Routes to Transit (SR2T) program, which funded enhancements to increase walking and cycling to regional transit stations. To understand how the program influenced travel choices, behavior, and perceptions of safety and local air quality, researchers surveyed transit users and observed driver, pedestrian, and bicyclist behavior in the periods before and after the enhancements were made at multiple transit stations. Data from the treatment and control stations suggest that the streetscape and roadway improvements made through the SR2T program positively influenced the propensity to walk, bicycle, and take the bus to transit stations as reported through surveys. In particular, results show that walking and bicycling increased by 3% among treatment sites compared with control sites. Bicycling also increased at control sites, indicating a general societal shift. Further, driving decreased 2.5% at treatment sites. Perceived air quality, in general, improved in the post-period. When asked about perceived traffic risk, bicyclists more than pedestrians reported feeling safer on the road, with 10% of the bicyclists, on average, feeling safer after the improvements. There were also economic benefits from this project—pedestrians and bicyclists were overrepresented in those who stopped en route to transit for food and drink. The evidence suggests that the SR2T program positively impacted the decision to walk and bicycle to access transit. It is recommended that the program be expanded to additional sites in the future.

2:45 p.m. - 4:30 p.m., Convention Center, Hall E
“Dynamic Programming-Based Pedestrian Hot Spot Identification Approach”
Aditya Medury and Offer Grembek, University of California, Berkeley, SafeTREC
Presentation: 15-4570; Poster Board Location: J12
Abstract: Network screening techniques are widely used by state agencies to identify locations with high collision concentration, also referred to as hotspots. However, most of the research in this regard has focused on identifying highway segments that are of concern to automobile collisions. A major difference between pedestrian and automobile hotspots is that pedestrian-based conflicts are more likely to arise in localized regions, such as near intersections, mid-blocks, and/or other crossings, as opposed to along long stretches of roadway. Hence, in order to address this issue, a dynamic programming-based hotspot identification approach is proposed which provides efficient hotspot definitions for pedestrian crashes. The proposed approach is compared with the sliding window method and the results reveal that the dynamic programming method generates more hotspots with a higher number of crashes, while covering fewer miles.