Road Safety Audits (RSA)

Road Safety Audit Case Studies: Using Three-Dimensional Design Visualization in the Road Safety Audit Process

Executive Summary

The purpose of this document is to help Federal, State, Tribal, and local agencies understand the benefits of utilizing interactive, three-dimensional (3-D) visualization to assist a road safety audit (RSA) team in performing a safety performance examination of potential roadway designs. This effort included performing four pre-construction stage RSAs in four different regions of the country that incorporated 3-D visualization in the standard eight-step RSA process (see Table 1).

Table 1: Pre-construction Stage RSAs Conducted Using 3-D Visualization

Three-dimensional models of the proposed concepts and designs were developed using digital terrain models, design surface models, associated 2-D or 3-D computer-aided design (CAD) files, and other information necessary to create a detailed rendering of the proposed roadway and surrounding environment. This included traffic control signs, pavement markings, lane configurations, major landscaping, roadside appurtenances, traffic signals, and other items within the right-of-way to render a realistic visualization of the roadway and its environment. The 3-D models were exported to a 3-D PDF format that allowed them to be viewed using Adobe software that is both free and readily available to the general public. Furthermore, the 3-D PDF controls were easy to use for someone with basic computer skills. The user could easily rotate 360 degrees while virtually "walking" or "driving" through stations spaced 100 feet apart along the proposed alignment. Using the technique of creating the model in the 3-D PDF format enabled the RSA team and roadway owner to share and review the 3-D models to ensure their accuracy.

The use of this tool during the RSA allowed team members to visualize the project designs and identify elements that may pose a safety concern to future road users. These elements can then be further discussed and evaluated during design phases, allowing changes to be more easily made to plans rather than after the roadway has been constructed.

Three-dimensional visualization can be a useful tool in assisting RSA teams to make a more thorough assessment of safety. When used effectively, the 3-D model is a tool that will save the RSA team time and yield a heightened awareness of safety issues related to the design project. In general, the benefits associated with 3-D visualization include the following:

• Enabling persons who are not proficient at reading roadway design plans to comprehend the proposed improvements This is particularly important for large, complex projects, innovative designs, significant differences in elevation and/or grade, unusual designs, and understanding key engineering concepts.
• Illustrating how proposed features (e g , signs, structures, and traffic signals) will affect the roadway environment.
• Allowing users to view the proposed conditions from a countless number of vantage points which may reveal issues not otherwise obvious from a review of standard 2-D plans.
• Providing visual support of the RSA team's findings and recommendations to the project owners, stakeholders, and others.
• Helping to maximize the effective time of the RSA team members.
• Understanding and visualizing inaccessible locations (due to weather, terrain, security restrictions, etc).
• Identifying potentially significant impacts to community, cultural, or historic interests and other sensitive areas.
• Providing another set of collective eyes to review the project designs and engineering studies.
• Promoting a holistic design process, ensuring that, if done early, potential design issues are identified and can be addressed in a timely manner, rather than late in the design process when changes can be timely and costly.

Moving forward, techniques are continually advancing the ability to utilize 3-D visualization. Future tools will be more efficient and graphic capabilities more advanced, which will allow the further integration of 3-D visualization in the RSA and other safety processes. It is recommended that 3-D visualization continue to be incorporated within RSAs of future/potential construction projects.