Illinois Develops Safety Performance Functions for Network Screening

Summary from: Roadway Safety Data Program | Development of Safety Performance Functions for Network Screening in Illinois

Background

In 2006, the Illinois Center for Transportation, Illinois Department of Transportation (IDOT), and the University of Illinois at Urbana-Champaign performed a research project to develop state-specific SPFs to use in the State’s network screening process. Prior to 2006, IDOT used the High Accident Location Identification System (HALIS) to identify High Accident Locations (HAL) and wet pavement cluster/segments that were based on crash frequency, rate, and equivalent property only. This project addressed the following specific challenges:

• linking crash and roadway data, given each had a different linear referencing system;
• establishing the criteria to assign each roadway segment to a peer group;
• using “reference points” to establish intersection locations;
• currency of crash and traffic data;
• processing a large volume of crash and roadway data; and
• helping users understand the meaning of the results.

Read the Case Study Development of Safety Performance Functions for Network Screening in Illinois for more detailed information.

Utah Collects and Uses Roadway Asset Data

Summary from: Roadway Safety Data Program | Collection and Use of Roadway Asset Data In Utah | FHWA-SA-14-078

Background

Quality data are the foundation for making important decisions regarding the design, operation, and safety of roadways. While crash data have been a consistent element of highway safety analysis, in recent years there has been an increased focus on the combination of crash, roadway, and traffic data to make more precise and prioritized safety decisions. The application of advanced highway safety analysis processes and tools requires a comprehensive inventory of roadway safety data combined with crash data to better identify and understand problems, prioritize locations for treatment, apply appropriate countermeasures, and evaluate the effectiveness of the those countermeasures. Comprehensive roadway safety data include information on roadway and roadside features, traffic operations, traffic volumes, and crashes.

Read the Case Study Collection and Use of Roadway Asset Data In Utah for more detailed information.

Virginia Develops and Uses State-Specific Performance Functions (SPFS)

Summary from: Roadway Safety Data Program | Developing and Using State-Specific Safety Performance Functions (SPFS) In Virginia | FHWA-SA-14-078

Background

The Virginia Department of Transportation (VDOT) emphasizes data-driven decision-making and desires to improve safety and safety data. From this desire, VDOT implemented a comprehensive set of State-specific Safety Performance Functions (SPFs) covering 98 percent of its State-maintained roadway locations. The impetus for VDOT developing their own SPFs and analytical tools arose from the decision that AASHTOWare Safety Analyst™ did not meet their needs. VDOT developed State-specific SPFs using historical crash, traffic, and roadway inventory data. SPF developers worked closely with engineers throughout the development process to see whether each SPF was implementable for all types of improvements (spot, corridor, and systemic). To date, VDOT has developed 24 SPFs covering a majority of roadway facilities, including two-lane roads, intersections, and freeways/multi-lane highways.

After performing network screening, the VDOT central office identifies the top 100 sections and top 100 miles of segments with the largest Potential for Safety Improvement (PSI). The list is then sent to the district engineers who determine which sites to prioritize based on practical experience and knowledge of their area. VDOT has noted several benefits of Virginia’s SPF implementation effort. For example, the advanced data-driven process leads to better use of funds, benefits for both systemic and spot improvements are quantifiable, VDOT can better manage public concerns, and VDOT can compare locations to prioritize projects. The SPF development team conducts training (including an annual “roadshow” to all nine districts) and hosts webinars to ensure district engineers understand the methodology and how to use the SPFs. VDOT has not mandated the use of SPFs and PSIs by the districts because the process of introducing a new methodology takes time, but the district engineers know it is the preferred method for network screening.

Read the Case Study Developing and Using State-Specific Safety Performance Functions (SPFS) In Virginia for more detailed information.

Utah Department of Transportation Uses Safety Data Processes and Governance Practices

Summary from: Roadway Safety Data Program | Utah Department of Transportation Safety Data Processes and Governance Practices | FHWA-SA-15-060

Background

The purpose of this case study is to highlight innovative data management strategies at Utah Department of Transportation (UDOT) that support the use of technology to benefit safety programs. In addition to highlighting forward-thinking strategies for safety data management, data analysis, and reporting, the case study documents the need for a formal data business plan and data governance. Exploring data management practices and the use of innovative tools within UDOT provides safety data management examples of:

• The importance and usefulness of a robust and well-managed data collection program.
• Providing access to integrated data for a variety of purposes.
• How to use integrated data to develop advanced safety analysis capabilities and at the same time support tools for planning, performance measures, and target-setting processes.
• The importance of collaboration and sharing current data strategies and challenges with data stakeholders.

Read the Case Study Utah Department of Transportation Safety Data Processes and Governance Practices for more detailed information.

New Hampshire Department of Transportation Uses Safety Data Systems and Processes to Improve Traffic Safety

Summary from: Roadway Safety Data Program | New Hampshire Department of Transportation Safety Data Systems and Processes | FHWA-SA-15-058

Background

The purpose of this case study is to highlight noteworthy practices of the New Hampshire Department of Transportation (NHDOT) in leveraging technology to enhance safety data management—in particular, NHDOT’s use of an integrated Linear Referencing System (LRS) and use of information technology (IT) tools to analyze safety data (e.g., AASHTOWare Safety Analyst™, American Association of State and Highway Officials (AASHTO) Highway Safety Manual (HSM), and Graphical Information Systems (GIS) tools). New Hampshire’s use of technology improves management of safety data systems by providing mechanisms for:

• Electronic data collection, thereby reducing data errors at the point of collection;
• Integration of data from different systems, using GIS and a consolidated LRS;
• Access to multiple types of safety data through a single portal that extracts and displays crash, traffic, and road inventory data; and
• Analysis of data for identification of high crash “hot spots,” or locations with potential for safety improvement, using safety performance functions to estimate expected crash frequency of all sites across the road network.

Read the Case Study New Hampshire Department of Transportation Safety Data Systems and Processes for more detailed information.

Michigan Department of Transportation Uses Safety Data Processes

Summary from: Roadway Safety Data Program | Michigan Department of Transportation Safety Data Processes and Governance Practices | FHWA-SA-15-059

Background

The purpose of this case study is to summarize how the Michigan Department of Transportation (MDOT) incorporates a data governance structure into their standard business operations and how it has helped them to improve their safety data systems and processes. “Data governance can be defined as the execution and enforcement of authority over the management of data assets and the performance of data functions” (NCHRP Report 666, 2010) and is an integral component used to facilitate management of data systems as part of an agency’s data business plan.

In the case of MDOT, a set of data governance practices provides the foundation needed to develop a comprehensive Data Business Plan, to support MDOT’s Strategic Highway Safety Plan Highway Safety Improvement Program, and improve information systems that manage data needed for safety analysis, planning, and decision-making.

Read the Case Study Michigan Department of Transportation Safety Data Processes and Governance Practices for more detailed information.

New Hampshire Develops Intersection Inventory to Improve Road Safety

Summary from: Roadway Safety Data Program | New Hampshire’s Intersection Inventory | FHWA-SA-15-087

Background

One of the major challenges transportation agencies face when trying to address intersection safety is not having a sufficient intersection inventory that provides location, operations, or geometrics of the intersections. In 2010, the Federal Highway Administration (FHWA) released the Model Inventory of Roadway Elements (MIRE), which is a recommended list of roadway and traffic volume data elements important to safety management and analysis. The New Hampshire Department of Transportation (NHDOT) was one of two States selected by FHWA to participate as a Lead Agency in the MIRE Management Information System (MIS) effort. FHWA conducted the MIRE MIS Lead Agency Program pilot project to test the feasibility of collecting, storing, and integrating MIRE data into an MIS and then linking roadway inventory data with crash and other relevant data for safety analyses.

NHDOT chose to focus their data collection effort on the acquisition of additional intersection elements to expand its use of AASHTOWare Safety Analyst™ primarily to support network screening analyses. After NHDOT completed data collection and integrated the data into the system, they now use the inventory for evaluating roadway safety countermeasures and for performing economic analysis. The intersection inventory supports better safety analysis using data specific to New Hampshire’s roadway network instead of default values or national averages. New Hampshire has benefitted from the state-specific data by targeting their spending by comparing sites and prioritizing locations with greater potential for improvement.

Read the Case Study New Hampshire’s Intersection Inventory for more detailed information.

Iowa Uses Real-Time Data Integration of Snowplow Information and Roadway Safety

Summary from: Roadway Safety Data Program | Iowa’s Real-Time Data Integration of Snowplow Information and Roadway Safety | FHWA-SA-16-030

Background

The Iowa Department of Transportation (DOT) deploys about 900 snowplows each winter to plow 9,479 centerline miles of road and 25,215 lane miles of roadway. The Iowa DOT continuously seeks ways to improve winter operations and provide information to the traveling public. A current effort involves the Iowa DOT deploying the Plow Cam Project—a statewide real-time integration system. The project, started in winter 2013-2014, involves collecting up-to-date photos that create a database of road conditions.

To gather this information, the Iowa DOT used its existing communications infrastructure and the snowplows deployed on a regular basis in the winter. The process also required an iPhone (with camera and GPS), an Iowa DOT-developed app, phone charger, cigarette lighter socket and fuse, and a suction cup phone mount. The iPhone is mounted inside the front windshield of the snowplow; once activated, it automatically takes photos and accumulates data.

The information collected from the snowplow cameras is available for internal and public use. The public accesses the information through its Track A Plow web site, which provides snowplow locations, as well as up-to-date Plow Cam photos.

Read the Case Study Iowa’s Real-Time Data Integration of Snowplow Information and Roadway Safety for more detailed information.

Colorado Uses GIS to Implement Level of Service of Safety

Summary from: Roadway Safety Data Program | Colorado’s Implementation of Level of Service of Safety: Strategies For Using GIS to Advance Highway Safety | FHWA-SA-16-027

Background

Design engineers at the Colorado Department of Transportation (CDOT) developed the LOSS method as an alternative to using crash rates for evaluating safety. The LOSS method compares a roadway segment’s observed crash frequency and severity to the crash frequencies and severities predicted by Safety Performance Functions (SPFs). Relying on crash rates alone to identify safety deficiencies is problematic because crash rates imply a linear relationship between exposure and safety. However, the number of crashes fluctuates based on traffic volume.

Transportation agencies that model crash frequency and severity based on annual average daily traffic (AADT) develop SPFs for public roadways, including segments and intersections. They stratify SPFs by the number of lanes, number of legs, traffic control, terrain, environment, and functional classification. Once transportation engineers and planners develop the SPFs, they can employ the LOSS method. While it is possible to segment roadway data in tabular form, using a Geographic Information System (GIS) greatly facilitates segmentation of these roadways. More specifically, GIS enables analysts to spatially link data describing roadway geometry with crash data. For intersections, it is necessary for analysts to use some special context to link intersecting roadways, as a tabular dataset cannot use GIS to link intersecting roads.

Read the Case Study Colorado’s Implementation of Level of Service of Safety: Strategies For Using GIS to Advance Highway Safety for more detailed information.

Tennessee Develops Horizontal Curve Database

Summary from: Roadway Safety Data Program | Tennessee’s Horizontal Curve Database | FHWA-SA-16-048

Background

In 2012, The Tennessee Department of Transportation (TDOT) accomplished its initial data collection for its entire roadway network, which includes all interstates, state highways, arterials, collectors, and local roads. With these data, TDOT created a horizontal curve database with approximately 40,000 miles of roadways with curves, which is housed in the Tennessee Roadway Information Management System (TRIMS)—a client-server application that allows TDOT to capture, maintain, and view critical roadway data. TDOT uses the horizontal curve database to provide quick, data-derived answers to public concerns, make data-driven decisions, quantify potential benefits from both systemic and spot improvements, and compare curves with similar characteristics to help prioritize projects.

Read the Case Study Tennessee’s Horizontal Curve Database for more detailed information.